Hydrologic Outlook – An Anomalously Warm And Increasingly Unstable Atmosphere Will Have To Be Closely Monitored For Additional Waves Of Heavy Rainfall In Coming Days
Although the chance for showers & thunderstorms will increase by mid-week ( Wednesday – February 21 ), and should be closely monitored, the highest risk for more heavy to excessive rainfall is currently timed for the February 24-25 period. Stay tuned for updates.
Monday Night Into Tuesday Morning
Partly-mostly cloudy. Windy. S-SSW winds 10-20 mph, with higher gusts, on mountain ridges-exposed plateaus below 2700 feet. SSW-SW winds 15-25 mph, with higher gusts, along mountain ridges above 2700 feet. Mild with temperatures widespread from low 50s to low 60s ( mid-upper 40s in coolest valley locations ).
Partly-mostly sunny. Unseasonably warm. Windy. Winds S-SW at 10-20 mph, with higher gusts. Temps varying from mid-upper 50s in upper elevations to the low-mid 70s.
Tuesday Night Into Wednesday Morning
Partly-mostly cloudy. Windy. SSE-SSW winds 10-20 mph, with higher gusts, on mountain ridges-exposed plateaus below 2700 feet. SSW-SW winds 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Mild with widespread temperatures in the 50s.
Mostly cloudy. A chance of showers & thunderstorms. Downpours possible. SSW-SW winds 5-15 mph, with higher gusts. Temperatures varying from 50s in upper elevations to the upper 60s to lower 70s.
Wednesday Night Into Thursday
Mostly cloudy. A chance of showers & thunderstorms. Winds SSW-SW at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges. Mild with widespread temps in the 50s to near 60 degrees.
Up to 73.0″ of snow ( at least, and likely more ) fell at the summit level of the High Knob Massif during February 2015 as a huge snowpack ( 3 to 4+ feet ) developed this week only three years ago. Air temps dropped to -23 degrees below 0 in Clintwood into morning hours of February 20, and very likely to below -30 degrees in high valleys of the massif ( * ).
*This was prior to the beginning of high-resolution data collection in high valleys of the massif as part of UVA-Wise undergraduate field research; however, observed differences between Clintwood and high valleys since that time suggests MIN temps would have easily been colder than -30 degrees below zero.
Although just over a foot of snow has fallen at the summit level of the High Knob Massif this month, it has really been all about heavy to excessive rainfall with a general 11.00″ to 13.00″+ observed in upper elevations above 3000 feet from the High Knob high country to the crest of Black Mountain.
A total of 7.68″ being measured in Clintwood ( just shy of the 8.08″ record established during February 2003 ).
Precipitation measured during Winter 2017-18, and this month, has been FAR from even across southwest Virginia as is so often the case ( it is part of long-term climatology ).
And it is not just due to Blacksburg being located within the valley of the New River, but also includes sites at the top of the plateau ( such as Bluefield ).
Totals of 6.63″ to 7.09″ in Blacksburg-Bluefield since the start of Meteorological Winter ( December 1, 2017 ) versus general totals of 21.00″ to 22.00″+ in the High Knob Massif during this same time.
It is a true orographic rain shadow effect, but along an axis that is oriented differently than textbook cases. During February, above, low-level air flowing into the High Knob Massif has arrived via the open expanse of the Tennessee Valley versus locations to the east in southwest Virginia where a SSW flow has to first cross the long axis of the TN-NC border, and SW North Carolina, where moisture extraction occurs. Looking at the entire winter season ( below ) a WSW component in low-levels means air must first cross the High Knob Massif and Cumberland Mountains before reaching locatons farther east in southwestern Virginia. Again, a shadowing effect.
Composite mean flow vectors reveal part of the reason as to why there is such a HUGE difference in precipitation across southwestern Virginia, between the High Knob Massif and sites farther east, with low-level 925 MB flow observed in February ( above ) and since the start of winter ( below ).
With a FOOT or more of precipitation already accumulated at upper elevations, it now is only a matter of how high will totals get before this month finally ends ( lets all hope and pray it can end without any more serious high water issues ).
Looking Ahead: Late Week-Weekend
There is significant concern for later this week. While many love warm weather, it is February and record level warmth is seldom ever a good thing in winter since it is a signal that the atmosphere is greatly out of balance and will be working to restore the balance ( the restoration of such being the problem since that = more rain upcoming ).
Since the GFS Model has recently been closest to actual rain amounts ( although it too under-estimated totals ), I will use it for a look ahead at possible rain yet to come through this weekend ( the GFS 21-Member Ensemble Mean is below ).
With the first CAPE of this year showing up in models, a concern is that thunderstorms will develop and/or become embedded within a rain shield to enhance amounts and the downpour potential.
This run of the GFS Model group shows that the operational run is pretty much in agreement with the 21-Member Ensemble Mean.
From low to upper levels a notable tropical connection is very visible on GOES-16 images ( an atmospheric river of moisture that needs only a focus to trigger release of its tremendous latent energy ).
Increased amplitude of the flow pattern shows up well on this 500 MB Earth View ( at link ), with a High pressure off the southeastern USA coast anchoring the flux of warm, moist air into the central-eastern USA.
Emergency Managers as well as everyone living along creeks and typical poor drainage, flood prone locales, will need to increase alert levels in coming days.
ALERT For High Water Levels Through Saturday Night Into Early Sunday
Note that 22 hours of missing data occurred during the flood event, such that the peak was both higher and broader than shown by the hydrograph of the stream level above ( blue line ).
Creeks are near flood stage ( a little below or above ) and will remain at high levels through Saturday night into Sunday, especially where around 1.50″ or locally more of rain fell in the High Knob Massif – Black Mountain corridor during Saturday.
As of 8:00 PM Saturday the stage was only 0.2 feet ( two-tenths of a foot ) below flood stage on Big Stony Creek in northern Scott County. This marks the third time that the creek has reach around or above flood stage in February, and unfortunately it is not likely to be the last time.
A total of 2.24″ of rain has been reported by the automated gauge at Big Cherry Dam since I measured the NWS rain gauge on Feb 14. This has pushed February precipitation to at least 12.21″ ( the 2018 total to nearly 18.00″ and the winter tally to more than 21.00″ ).
ALERT For Strong Rises On Streams During Saturday Afternoon-Evening And Possible Flooding
Moderate-heavy rainfall will develop and spread across the mountain area Saturday. Due to saturated conditions, and near record February precipitation amounts, strong rises on creeks are expected. Mud-rock slides & local power outages will also be possible.
Remain alert to NOAA weatehr radio and your favorite media sources for possible warnings that may be needed.
Overnight Into Saturday Morning
Low clouds. Areas of dense fog ( widespread at the upper elevations ) and drizzle into the overnight, with freezing fog-drizzle at highest elevations before temps begin rising by morning. Winds N-NE at 5-10 mph into the overnight, then shifting SSE to SW at 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures in the 30s ( around 30 degrees at highest elevations before rising toward morning ). Wind chills in the 20s to low 30s.
Saturday Morning Through The Afternoon
Rain developing by the predawn-morning. Heavy at times into the afternoon. Areas of fog. Winds becoming variable at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges-plateaus. Temps in the 30s to lower 40s.
Saturday Night Into Sunday Morning
Rain during the evening ( heavy early ) tapering off to showers & drizzle into the overnight. Turning colder with freezing fog-drizzle at upper elevations. Winds NW to N at 5-15 mph, with higher gusts. Temperatures dropping into the middle 20s to middle 30s ( coldest highest elevations ). Wind chills in the 10s and 20s on higher mountain ridges.
Sunday Morning Through The Afternoon
Low clouds & fog giving way to partly sunny skies ( high clouds ). Warmer. Winds SE-S at 5-15 mph, with higher gusts. Temperatures in the 40s to low-mid 50s ( coolest upper elevations ).
Sunday Night Into Monday Morning
Increasing clouds with rain showers developing overnight into morning. Windy. SSE-S winds 10-20 mph, with higher gusts, along mountain ridges-exposed plateaus below 2700 feet. S-SW winds 15-25 mph with higher gusts on mountain ridges above 2700 feet. Temperatures varying from the low 40s to low 50s ( falling into 30s in sheltered valleys during the evening before rising ), tending to rise toward morning.
The currently forecast upper air pattern into next week continues to look most favorable for another high water event, with deep tropical moisture set to generate additional heavy to excessive rainfall. See my updated discussion below for more details.
Weather Discussion ( More R+ )
Sometimes the atmosphere gets stuck in a rut, and in this case it means more heavy rain for locations that need not nary another drop!
Rainfall totals during Friday ranged up to around 0.80″ at Big Cherry Dam of the High Knob Massif, pushing the total for February up to around 11.00″ . Locally higher amounts have also occurred in the high country along the Wise-Scott border ( and the month has 12 more days to go ).
These excessive rain amounts have, of course, not been just restricted to the high country with more than 9.00″ having now occurred in February at the Big Stone Gap Water Plant and the Appalachia Lake Water Plant.
Forecast models are again converging upon this area once more for the heaviest rainfall amounts through Saturday.
Forecast amounts of 1.00″ to 2.00″ would not typically be a great concern, but during a month when MAX precipitation amounts are approaching a FOOT in headwater creek basins it has to be taken with respect. It is good that NWS Forecast Offices have come together to post a Flood Watch ahead of this system ( especially since locally heavier amounts will be possible due to orographics and the seeder-feeder process I highlighted in the previous discussion ).
Reference My 021418 Forecast to read about the Seeder-Feeder Precipitation Process and to see recent orographic feeder clouds.
Once more, a signal that rainfall will again become heavy is a connection to the tropical Pacific Ocean as shown well by this GOES-16 Mid-Level Water Vapor Image:
This shows up well on the current ( as of Midnight Feb 17 ) streamline flow fields at 700 to 500 MB across the Earth:
The only good news is that the system will be progressive and moving along, with around a 12-hour window where rainfall will have the potential to be moderate-heavy in between chilly air ( currently felt and again to be felt by later Saturday Night into Sunday Morning ).
This pattern is truly stuck in a rut between blocking ridges of High pressure.
One blocking High off the southeastern USA coast is acting as a latent heat ( energy ) pump, with anomalous moisture and warmth streaming into the SE USA.
The other blocking High, over the Gulf of Alaska and Aleutians, is threatening to keep a SW upper air flow locked across the United States through the extended forecast period ( with a Pacific moisture connection ).
I continue to be worried about this forecast setting, which will feature a heavy to excessive rain potential for locations from the Mississippi Valley into at least the western side of the Appalachians ( where flooding has already occurred, as you well know ).
ALERT For A Continuation Of Strong SW Winds At Mid-Upper Elevations During Thursday Night Into Friday, With Increasing Gusts Into Lower Elevations During The Overnight-Predawn Of Friday
A strong SW flow of air will continue in advance of an approaching cold front through Thursday Night into the morning hours of Friday before a wind shift to W then N directions occurs during the day Friday. Local power outages will remain possible.
The leading edge of this front may be marked by a line of heavy rainfall, followed by widespread rainfall of lesser intensity. Remain alert for possible water level rises.
An ALERT For DENSE Fog Is Likely For Late Friday Into Friday Night With Dropping Cloud Bases On Northerly Upslope Flow Along & North Of The High Knob Massif And Tennessee Valley Divide ( A Limited Period )
Hydrology ALERT For Significant Rainfall Amounts
A moist low-level air mass will combine with strong SW winds to produce rain showers at times through coming days. Downpours will be possible, especially within the upslope corridor along and southwest of the High Knob Massif & Tennessee Valley Divide.
A large region with significant rainfall will be possible during the next 5-7 days, with heaviest amounts expected to again fall along and west of the Appalachians from the mountains to Ohio River.
Due to saturated conditions in wake of recent flooding persons living along streams and in low-lying, flood prone locations will need to remain alert for the possibility of water level rises.
ALERT For Dense Fog Across Mid-Upper Elevations And Within The SW Flow Funneling Zone Along U.S. 23 At Powell Valley Overlook
Dense fog was present throughout the daylight hours of Wednesday along the flanks of the High Knob Massif and highest elevations, as well as within the Head of Powell Valley where SW flow rises to funnel through Little Stone Mountain Gap ( on either side of Powell Valley Overlook ).
This has been causing a sudden reduction is visibility along U.S. 23 such that caution is advised for those traveling between the Town of Big Stone Gap and City of Norton.
Overnight Into Wednesday Morning
Cloudy and windy. Rain developing with a chance of downpours. Low clouds with widespread dense fog at upper elevations. SSW to SW winds 10-25 mph, with higher gusts. Temperatures widespread in the 40s to around 50 degrees.
Wednesday Morning Through The Afternoon
A chance of rain showers. Local downpours possible. Low clouds with dense fog at high elevations. SSW-SW winds 10-20 mph with higher gusts. Temperatures in the upper 40s to middle 50s.
Wednesday Night Into Thursday Morning
Rain showers. Downpours possible. Low clouds with dense fog at mid to upper elevations. SW winds 10-20 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. SW-WSW winds 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Unseasonably mild with temperatures mainly in the 50s.
Thursday Morning Through The Afternoon
A chance of rain showers. Downpours possible. Low clouds with dense fog at upper elevations and in SW upslope flow sites at mid elevations ( e.g., Powell Valley Overlook ). SSW-SW winds 15-25 mph, with higher gusts. Unseasonably mild with temperatures from the low 50s to the low 60s.
Overnight Into Friday Morning
Mostly cloudy. Windy. Unseasonably Warm. Chance of showers developing toward morning. SW Winds 15-30 mph, with higher gusts. Temperatures in the 50s to lower 60s.
Friday Morning Through The Afternoon
Morning rain, heavy at times. Windy. Turning colder with rain tapering to showers or a mix. Rain changing to snow at the upper elevations by mid-late afternoon before ending, or becoming flurries. Morning temperatures in the 50s to lower 60s dropping sharply during mid-late afternoon into the lower 30s to lower 40s ( coldest highest elevations ). A drop in cloud bases with dense fog formation for a period during late afternoon-early evening at elevations above 2500-3000 feet. Developing mid-later afternoon wind chills in the 20s & 30s.
Friday Night Into Saturday Morning
Low clouds & fog giving way to mostly cloudy skies. Areas of dense fog possible at low elevations. Winds becoming light & variable. Temperatures varying from low 20s to lower 30s ( coldest in upper elevations ).
*Another wave of rain, with locally heavy amounts, is expected to overspread the area during Saturday. This could cause strong rises on creeks.
The currently forecast upper air pattern into next week continues to look most favorable for another high water event, with deep tropical moisture set to generate additional heavy to excessive rainfall. See my updated discussion below for more details.
Weather Discussion ( Wet Pattern )
Thursday Night ( Feb 15 ) Update
A couple more rain producing systems will be crossing the mountain area into this weekend, with strong SW winds in advance of the first system into Friday morning.
A general 1.00″ to 2.00″ of rain will be possible with these two waves ( heaviest amounts centered on the morning to early afternoon hours of Friday and again Saturday afternoon-early Saturday evening ).
Due to orographic clouds capping high elevations, and moderate to strong lift, locally higher rain amounts will be possible. What do I mean by orographic clouds?
Once higher level clouds dissipated the orographic capping clouds became visible. Note how the cloud bank stretched across the High Knob Massif ( above ) is stationary over time ( below ), indicating that it is being supported by orographic lifting on strong SW flow ( in this case ).
This is part of an important seeder-feeder precipitation process in which rain falling out of a higher altitude seeder cloud falls down through the moisture rich environment of the feeder cloud and becomes enhanced, with more rainfall subsequently reaching the surface than falls out of the seeder clouds ( and more than is able to be detected by Doppler radar whose beam shoots over top the orographic feeder clouds capping the high country ).
This is part of the reason why rainfall is always under-estimated for the High Knob Massif area, with my climatology showing that this process is important throughout the year but especially in the orographic forcing season ( November-April ) when strong winds generate long-lived orographic cloud masses.
People living along streams, and in low-lying poor drainage locations, will need to remain alert for water level rises into Friday afternoon and again later Saturday into Saturday night. Given general 5.00″ to 10.00″+ amounts already observed this month, it will not take as much rain to generate water level rises.
As noted above, I continue to think next week will offer a more serious threat to the mountain region with more heavy to excessive rainfall becoming likely.
Although specific rainfall forecasts vary from run to run and among models, and no single model run should be taken as being accurate ( like above ), composite ensemble means for the European Model group and GFS are again showing a strong signal for heavy to excessive rainfall amounts.
A western Atlantic High, analogous to a summer-like Bermuda High, in combination with a deep upper air trough anchored by Gulf of Alaska ridging is truly an ominous signal for heavy-excessive rainfall from the mountains west to the Mississippi River.
A wet pattern will continue to dominate the mountain region through coming days, with a strong SW air flow helping to enhance the potential for showers and local downpours. While a change in the flow is expected to briefly occur by late week-early this weekend, an even more potent flow with a deep, tropical connection may develop by next week. A truly worrisome pattern.
A general 2.50″ to 3.00″ of basin average rainfall is now expected from the High Knob Landform west & northwest during the next 5 to 7 days. Like during the previous event this is a broad generalized composite of model forecasts and does not fully account for orographic forcing.
*Low clouds ( widespread fog in orographic clouds ) currently engulfing much of the high country are expected to be a notable feature through coming days, signaling that an efficient seeder-feeder precipitation process will be in place to help enhance rainfall amounts with orographic forcing on strong SW flow.
All forecast models under-estimated rainfall amounts during the previous event, with the GFS Model being the closest to final storm totals ( it was still up to 3.00″ lower than MAX amounts observed in the High Knob Massif ).
The current pattern has Gulf of Mexico & Atlantic moisture inflow ( as observed by the 7 PM Tuesday 850 MB chart ) plus a connection to the tropical Pacific Ocean as seen on this full view of the Earth ( Western Hemisphere ).
Since I created this website I have had an Earth Flow Field Tool Embedded, and if you have not been using it then you have missed a great resource to view the big picture.
Note this tool is interactive. The Earth can be rotated in any direction and different parameters can be selected for viewing by clicking the word EARTH. Once selected, click the word EARTH again to remove the selection panel for complete viewing.
Next week it currently appears that the flow field will become even more conducive to tapping deep tropical moisture from the Pacific + Gulf of Mexico, as we now refer to as an Atmospheric River. We must hope this changes, and that rainfall during the next 3-5 days will be manageable.
This February is on pace to become the wettest on record. Reference The High Knob Landform for a look at the wettest.
ALERT For Dense Fog Formation & Freezing Fog-Drizzle At Middle To Upper Elevations Along And North of the High Knob Massif And Tennessee Valley Divide Into Monday Morning
A shift to northerly upslope flow behind the passage of a cold front will drop cloud bases and temperatures into the predawn-morning hours of Monday. Light freezing rain or drizzle, and freezing fog, will be possible at middle to upper elevations along and north of the High Knob Massif.
3:00 PM Monday Update – A nearly isothermal atmosphere has developed with temperatures +/- 2.0 degrees of 32 F degrees from Clintwood ( 1560 feet ) all the way up to the summit level of the High Knob Massif ( 4223 feet ).
Lonesome Pine Airport ( LNP ) has been having sensor problems, such that the following temperatures ( near the Airport on Pole Bridge Road ) are the most accurate:
Some places in Scott and Lee counties have been experiencing persistent cloud breaks, but that is due to downsloping off the high country of the High Knob Massif on NE air flow.
Moisture beneath a low-level temperature inversion will threaten to keep conditions cold and damp Monday, with best odds of this happening in locations along and north of the High Knob Massif-Tennessee Valley Divide where low-level northerly air flow will be rising and cooling.
ALERT Continues For High Water Levels Across The Area With Flooding On Main Stem Rivers Into Monday
Although water levels along headwater creeks are dropping, the danger has not yet passed with ROARING water gushing on creeks draining the High Knob Massif-Tennessee Valley Divide. A recap of some rainfall totals reveals why ( noting IFLOWS tend to read low ):
Storm Rainfall Totals February 10-11 Flood
Georges Fork: 3.80″ ( John Mullins )
Clintwood 1 W: 3.90″
Fort Blackmore IFLOWS: 4.16″
Big Stony Creek IFLOWS: 4.22″ ( SE Base of High Knob Massif )
Herald IFLOWS: 4.31″ ( Sandy Ridge )
Pole Bridge Road: 4.54″ ( Layton Gardner – Wise )
Stone Creek IFLOWS: 4.78″ ( Lee County )
Ben Hur IFLOWS: 5.24″ ( Lee County )
Little Mountain IFLOWS: 5.24″ ( Route 237 )
Black Mountain Mesonet: 5.35″ ( Near Harlan-Wise Line )
*Big Cherry Dam IFLOWS: 5.40″
Robinson Knob IFLOWS: 6.65″ ( High Chaparral-Robinson Knob Communities )
*Prior to this big storm event I measured 8.08″ at Big Cherry Dam during January 1-February 9, some 14% more than the IFLOWS and both totals are too low due to wind induced under-catches caused by air blowing across the Dam. I hope to add an Alter Shield to the NWS hand-measured gauge at some point this year to help reduce some of these losses due to wind ( the Black Mountain Mesonet site has an alter-shielded rain gauge ).
Flooding was especially bad in the Ramsey-Tacoma-Coeburn valley corridor as MAX reported storm rainfall fell over the headwaters of the Clear Creek and Burns Creek watersheds of the Guest River basin & the Little Stony Creek watershed of the Clinch River basin ( Guest River is also a tributary of the Clinch River but first cuts through Guest River Gorge of the High Knob Massif prior to joining the main river ).
Other areas with significant flooding were along and down-stream of the South Fork of Powell & Big Stony Creek basins in the Cracker Neck-East Stone Gap to Big Stone Gap section of Wise County and the Ka-Fort Blackmore section of Scott County ( translating to general main-stem river flooding along both the Clinch and Powell ).
During our UVA-Wise undergraduate field research trip on February 9 ( reference notes below ) rather extensive snow cover was documented from Bowman Mountain ( head of Clear Creek basin ) across High Knob Lake basin into the basin of Big Cherry Lake. Snow core data found 1.00″ to 2.00″ locked in the snow, meaning that roughly 1.50″ of water was added to totals reported from Robinson Knob southwest to Big Cherry Dam ( creating effective storm totals of 7.00″ to 8.00″ from these headwater locations ).
Very few places on Earth could handle 7.00″ to 8.00″ of water input without causing flooding, and it is actually amazing ( incredible ) that flooding was not more severe. The only explanation being that max rainfall and snow melt run-off occurred from basins that are heavily forested with trees ( and in the case of Big Cherry Lake basin, have valleys filled with water absorbing Sphagnum moss species ).
And I will state with absolute certainty, if these head- water locations had not been heavily forested, intact watersheds that flooding would have not only been MUCH more severe but likely deadly.
This is simply a critical point that can not be denied and should be considered by all in light of a pending 7,464 acre project planned to impact the Clear Creek-Burns Creek basins with notable logging & burning.
Mountain Area Forecast ( Feb 12-13 )
Overnight Into Monday Morning
Lowering cloud bases. Turning colder. Showers changing to freezing rain & drizzle. Dense fog and freezing fog at mid to upper elevations along and north of the High Knob Massif. Winds shifting NNW to NNE at 5-15 mph with higher gusts. Temperatures dropping into the middle 20s to low-mid 30s, coldest at upper elevations. Wind chills falling into the 20s, with 10s at upper elevations.
Monday Morning Through The Afternoon
Low clouds & chilly. Damp. Winds N-NE at 5-15 mph, with higher gusts. Temperatures nearly steady in the 20s to low-mid 30s. Wind chills in the 20s to around 30 degrees, except colder at high elevations.
Monday Night Into Tuesday Morning
Partly-mostly cloudy. Areas of fog. Chance of light rain or freezing rain showers. Winds shifting to E-SE at 5-10 mph, with higher gusts, along mountain ridges and exposed plateaus. Temperature falling slowly in mountain valleys to near steady-rising along mountain ridges and exposed plateaus in the 20s to low-mid 30s. Rime formation again within upper elevations ( above 3300 feet ).
Mostly cloudy. Chilly. Small chance of a rain shower. Winds SSE-SW at 5-15 mph with some higher gusts. Temperatures in the 30s to lower 40s.
Previous Flood Statements & Updates:
Mountain Area Flood Watch
12 Midnight Update – Sunday ( February 11 )
A general 3.00″ to 5.00″+ of rain has now fallen across the mountain area, from Wise-Scott-Lee counties into Dickenson County ( I measured 3.25″ as of 2345 hours on February 10 ) and the situation is getting worse in many places as rain and run-off continues.
*I have had water from the creek that goes by my home beneath the house at least 3 times during past years, and I fully understand the pain, misery, fear or whatever you may feel in these situations as the stream gradients here in the mountains add greatly to the danger of flowing flood waters. So please DO NOT take chances, as a single slip of the foot could be deadly, let alone even thinking about trying to drive through any flood waters.
We have had some trees and limbs fall, in addition to mud-rock slides to add complications to increasing flooding. If you are in a safe place now, please stay there. If you live along a creek, like I do, it will be a LONG night. Water levels have to be closely watched but please do not take unnecessary chances.
Know that current river levels forecasts are likely going to have to be adjusted UPWARD, as the full magnitude of this event becomes more apparent.
Note that while the main-stem Powell River in Big Stone Gap was last reported at around 10 feet, my records show that flooding typically begins on the South Fork of Powell in East Stone Gap and portions of Powell Valley when the level goes above 6.0 feet ( to indicate how serious this current setting is becoming ). Another indicator is that the spill-way at Big Cherry Dam is now reporting around 1.5 feet of overflow, which is huge given the width of the overflow, and its increasing!
*The South Fork of Powell is a subterranean stream; however, yesterday the below ground conduits were already full and the river running completely above ground. Always a bad signal in advance of a heavy precipitation event.
I like ( hate, but you know what I mean ) the HRRR Model prediction of future rainfall in the next 15-hours better than the NAM and new GFS which have been ( along with the ECMWF ) under-estimating rainfall rates ( the former GFS runs doing better on basin average amounts by the conclusion of this event…not up to this point in time! ).
Air temps are the warmest of this event at elevations above 4,000 feet, indicating a more buoyant and totally saturated column that will be productive in generating more rain, with a focus overnight into Sunday morning toward the major mountain barriers ( High Knob Massif-Tennessee Valley Divide ) on gusty and upsloping SW winds.
While this may help Dickenson, northern Wise, and Buchanan counties by offering at least the chance for more downslope forced lulls or weakening of radar echoes, it is not good news for much of Wise County, northern-central Scott and Lee counties.
It is obvious, but should be noted that since the Tennessee Valley Divide forms the southern border of Dickenson County and the top of the Russell Fork Basin watershed ( Sandy Ridge to Hazel and Big A mountains ) that is not good news for main-stem rivers. Highest rainfall totals so far in Dickenson have fallen along the top of the basin, meaning all that run-off has to drain downstream on the Pound, Cranes Nest, McClure, and Russell Fork…with a notable convergence in the Haysi area where the McClure and main-stem of the Russell Fork meet ( outflow from John Flannagan Dam then enters the Russell Fork downstream toward Bartlick ).
*If you still doubt SW flow is important, I reference the great April 1977 Flood Event ( the benchmark ) which was dominated by SW flow. While all locations in the echo training corridor had excessive rainfall amounts, greatest totals were within upslope locales.
Lifted indecies drop below zero, meaning that I will have to introduce the possibility that thunder ( convection ) may be a factor Sunday until a cold front passes and introduces a notable drop in temperatures Sunday Night-Monday AM.
We must all hope and pray that convection, thunder, does not develop Sunday as that could exacerbate the situation where ever such activity forms ( even across downslope locations ).
5:00 PM Update – Saturday ( February 10 )
I have now had 2.00″ of rain in Clintwood and the IFLOWS are running behind actual totals. That should be noted due to the heavy, fine, fasting falling nature of this type of rain.
Many creeks in the area are now near or beginning to go above flood stage ( the creek beside my house, only a tertiary stream, is approaching its flood stage ).
The highest automated rain gauge total is now 2.62″ from the Robinson Knob community of the High Knob Massif; however, at least 3.00″ has likely fallen ( * ).
*Otis & Nancy Ward measured for years by hand near this IFLOWS in Robinson Knob and consistently measured 10-20%+ more.
The bottom line, while totals are important it is going to become moot as the area goes into flood with still a long corridor of moderate-heavy rain upstream.
10:00 AM Update – Saturday ( February 10 )
As of 10 AM Saturday a general 1.00″ to 1.50″ of rain has fallen along the High Knob Massif in the past 12 hours, above model forecast’s for this time period.
*Specific Automated Totals Include:
Big Stony Creek: 1.62″ Robinson Knob: 1.43″ Little Mountain: 1.04″ Fort Blackmore: 1.04″ Big Cherry Dam: 0.92″ Dungannon: 0.88″
*Automated IFLOWS totals tend to be somewhat less than hand-measured amounts, especially when downpours occur as recently observed along the Wise-Scott border area.
Heaviest rainfall is currently expected to develop by later Saturday afternoon into Saturday Night-Sunday Morning, with a long feed of moisture streaming northeast from the Gulf of Mexico. Snow continues to retain water at highest elevations, with the main release likely to occur by late Saturday into early Sunday. Significant spikes will be possible on Big Stony Creek & South Fork of the Powell.
Hydrologic Outlook – A Heavy To Excessive Rainfall Pattern Will Be Developing From This Weekend Into Next Week With Multiple Waves Of Rain Creating A Setting Favorable For High Water And Flooding
The above is a generalized broad-brush of the upcoming rainfall pattern from the Weather Prediction Center, without factoring in complex terrain features and orographics beyond a larger-scale.
While specific models may vary on exact rain amounts from run to run, there is scary agreement in the focus of heavy to excessive rainfall being concentrated along western slopes of the southern Appalachians, as depicted by NOAA with a composite view above during the next week. This does not factor in local orographics or the snow melt water that will also be added during the next couple of days.
Local Setting – Mesoscale Discussion – February 9
From my perspective all EMS officials need to plan for the worst case scenario and hope for the best, with moderate to strong orographic forcing being forecast by terrain models during the next 48-hours ( the initial rounds of this event ).
To simplify, a strong and moist low-level air flow will be streaming into the Cumbeland Mountains on wind speeds currently forecast to be SW at 30-40 knots at elevations above 3000 feet. This will enhance lift of air into the High Knob Massif-Tennessee Valley Divide corridor ( which includes Black Mountain ) to impact headwaters of the Clinch, Powell, Russell Fork and Cumberland rivers within this area.
People living along creeks draining to these rivers, in addition to those along these main-stem rivers, will need to remain alert for strong water level rises this weekend. Please stay tuned to local officials and the NOAA Weather Radio ( and favorite media sources ) for possible warnings that may be needed by later Saturday into Sunday.
Snowpack Update – Snow Core Data
A substantial amount of concentrated snow remains across the High Knob Lake and Big Cherry Lake basins in the high country of the High Knob Massif as of February 9 ( PM ).
This despite more than 1.50″ of rainfall during February 7-8 ( approximately 3.00″ of precipitation at Big Cherry Dam so far in February, with 8.08″ so far this year ).
A clean snow core found 0.40″ of water content per 1″ of snow depth, with a general 3″ to 5″ of snow depth remaining across the High Knob Lake basin into a significant portion of the sprawling Big Cherry Lake basin ( ice-packed to slushy snow remained on the road at elevations above 3000 feet downstream of Big Cherry Dam toward the Big Stone Gap Water Plant ).
Previous snow melt pushed Big Stony Creek to 0.7 feet above flood stage in wake of a general 1.50-1.75″ of rain, with added snow melt resulting in the stream response observed by the gauge ( above ).
While the bulk of deepest and most widespread snow melted away, what remains is concentrated and will add locally to run-off into both the Clinch River and Powell River.
My recorded amount of 16.5″ of snow on Eagle Knob during the January 29-February 5 period looks on target, if not too low given what a larger survey by our UVA-Wise research students found Friday afternoon ( with 6″ to 12″ drifts still measured in numerous places from the High Knob Peak to Big Cherry Dam ).
Rainfall From Different Forecast Models
The 7 PM Friday run of the European Model is forecasting 2.50″ to 4.50″ of rain along the Cumberland Mountains during the next 48-Hours ( ending 7 PM Sunday ).
ALERT For Slick Patches Developing On Roadways With Dropping Temperatures Wednesday Evening
Caution is advised for those planning to travel through Wednesday Night with a combination of dropping temps and upslope snow showers and flurries.
ALERT For High Water Levels Along Creeks Draining The High Knob Massif Into Thursday Morning ( Feb 8 )
The combination of significant rain and melting snow has pushed stream levels above flood stage in local areas, with ROARING whitewater along creeks draining the High Knob high country along both sides of the Wise-Scott border.
The Big Stony Creek stream gauge in northern Scott County crested 0.7 feet above flood stage, the highest level observed in 2018, and is expected to begin declining Wednesday evening as below freezing air increases and the freezing level drops.
Although snow cover continues to be solid across northern slopes at upper elevations, and patchy on south slopes, and air temperatures have now dropped below freezing again at upper elevations, run-off will maintain high but declining levels on creeks through Wednesday night.
Strong Rises On Creeks, Especially Those Draining The Snow Covered High Knob Massif, Will Become Possible By Wednesday Afternoon
A live view from Eagle Knob of the High Knob Massif shows that clouds are engulfing upper elevations. Air temperatures have been below freezing all day until recently, with a climb to around and just above 32 degrees.
Substantial snow covering upper elevations across Black Mountain and the High Knob Massif will be melting with significant rain and dense fog into Wednesday.
People living along creeks draining the high country will need to remain ALERT for strong water level rises during Wednesday before colder air returns to diminish run-off.
Alert For Strong SSE-SW Winds Developing During Tuesday Night Into Wednesday Morning
A tightening pressure gradient in advance of significant rains will generate strong winds at mid-upper elevations, beginning first in upper elevations and working downward through middle into the lower elevations ( especially locally where mountain waves form ) during Tuesday night into Wednesday morning.
Overnight Into Tuesday Morning
Increasing and lowering clouds overnight into morning with a small chance of light snow or mixed precipitation. Windy across higher mountain ridges. Winds S-SW at 5-15 mph with higher gusts on mountain ridges-plateaus below 2700 feet. Winds SW-WSW 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Temps varying from 20 to 25 degrees to around 30 degrees, tending to rise overnight into morning. Wind chills in the 10s and 20s, except single digits along highest mountain ridges.
Mostly cloudy. Chilly. Generally light & variable winds. Temperatures in the 30s to lower 40s ( struggling toward freezing at highest elevations ). Wind chills in the 10s to lower 20s at highest elevations.
Tuesday Night Into Wednesday Morning
Rain developing. Becoming windy. Rain may be heavy at times overnight into morning. A chance of thunder. SSE to S winds 10-20 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. Winds S-SSW 20-30 mph, with higher gusts, on mountain ridges above 2700 feet. Temps near steady or slowly rising from the 30s to low-mid 40s. Areas of dense fog, especially at upper elevations. Wind chills in the 20s and 30s. Nasty!
Wednesday Morning Through The Afternoon
Rain, heavy at times, tapering to showers and drizzle. Turning colder. Rain changing to snow showers or to freezing drizzle at by late afternoon. Widespread dense fog at higher elevations. SW winds shifting NW at 5 to 15 mph with higher gusts. Temperatures falling back through the 30s ( into 20s at upper elevations by mid-late afternoon ). Wind chill factors dropping into 10s & 20s ( coldest at highest elevations ).
Wednesday Night Into Thursday Morning
Low clouds. Turning colder with snow showers & flurries. Snow accumulations mainly less than 1″, with some locally higher amounts possible. Winds WNW to NW at 5-15 mph, with higher gusts. Temps dropping into the low-mid 10s to low-mid 20s ( coldest at highest elevations ). Low clouds with rime formation at upper elevations. Wind chills dropping into the 10s to lower 20s, with single digits at upper elevations.
Hydrologic Outlook – A Heavy To Excessive Rainfall Pattern Will Be Developing From This Weekend Into Next Week. Please Stay Tuned For Later Updates.
A Watch For A Major Arctic Outbreak Impacting The USA May Be Needed Within The Next Week To 10 Days ( refer to my weather discussion section for more details ).
Weather Discussion ( Volatile Pattern )
Wednesday Afternoon Update
Falling temperatures ( 20s as of 5 PM at upper elevations in the High Knob Massif ) is causing a relatively rapid drop in freezing levels. This is good to help reduce run-off where creeks draining the High Knob Massif are simply ROARING. On the other hand, this is bad news since it will generate slick patches on area roadways.
Main concerns through Wednesday evening center around the possibility of slick conditions developing with freezing of moisture on roadways ( State Route 619 is already getting slick at highest elevations ), so caution is advised for those traveling, as well as for those who may live or be around the high water levels on creeks draining the massif along both sides of the Wise County-Scott County border.
The most exciting period of Winter 2017-18 is upcoming, with a highly volatile pattern taking shape across the Northern Hemisphere through the next few weeks.
Really the excitement has already been observed, with up to 5″ of new snow falling at the summit level of the High Knob Massif during the predawn-morning hours of Sunday.
Conditions were wicked, with air temps in the low-mid 20s and strong S-SW wind gusts over 30 miles per hour. Snow continued into mid-morning before changing to freezing rain and then rain.
Layton Gardner reported around 1″ of snow at his station near Lonesome Pine Airport, while I measured only 0.5″ in Clintwood as snow became mixed with sleet and freezing rain before changing to rain.
Heaviest snow in valleys actually fell along the windward side of the High Knob Massif with respect to S winds, with a corridor from the Duffield Valley to Fort Blackmore picking up significant snow as air was being forced to rise upward over not only the massif but an orographic standing wave which developed along the high country.
Although temperatures aloft were going above freezing to cause snow to transition to sleet, freezing rain, and rain in all locations surrounding the High Knob Massif in far southwestern Virginia, the formation of an orographic wave over & along the windward side of the massif forced air upward and over the wave, with this rising generating enough cooling to overcome the transport of warming air at and above the 875-825 MB layer.
Like water rolling off a breaking ocean wave approaching the beach, air was sinking upon crossing the wave crest and high country to generate a change into mixed precipitation toward Wise and Clintwood ( which received significantly less snow than Duffield and places on the Clinch River, in northern Scott County, which tend to be robbed of snowfall when air is flowing out of WNW to NE directions ( and sinking down off the high country ).
A majestic sun dog, formed by the refraction & scattering of light through high altitude ice crystal clouds, produced a rainbow of beautiful color above UVA-Wise Monday afternoon.
The second part of this system, which appeared to be the easiest to forecast, actually ended up producing much less NW flow snow than predicted. Joe Fields measured 0.5″ of new snow in the High Chaparral community, with around or just over 1″ on Eagle Knob, while much of the area had only a dusting. Roads were still slick with freezing from lingering moisture and what little snow that did fall.
Deposition of cloud vapor ( below ) added to moisture in the high country where riming, as so often occurs, developed once again in sub-freezing air. Deposition releases 680 calories of heat energy per gram into the atmosphere, so despite such cold conditions the process of rime formation is actually exothermic in nature and releases heat into the air ( perhaps a warming thought to keep in mind the next time you are up there and think “something” is just going to drop off your body in this dang cold air!!! ).
Now attention turns toward another nasty looking system which will spread significant rain across the mountain area Tuesday Night into Wednesday as a band of heavy snow sets up along and north of the Ohio River.
A local concern is a significant amount of snow ( as noted above ) on the ground across the high country, with depths generally varying from 2″ to 3″ on southern slopes at the 3000 to 3300 foot level to 4″-8″+ above 3300 feet on north slopes and at highest elevations ( all slopes ). The water content of this snowpack has had time to build, with the bottom oldest snow layer having been deposited during January 29-30 ( so rime + rain has been added over time ).
Snow is deep enough to absorb quite a bit of rain and the melt period will be somewhat less than 24-hours before temperatures drop below freezing again. Dense fog vapor, within orographic clouds; however, is always a concern.
*Latent heat of condensation can be a powerful agent applied to melting, so this situation will bear close watching with respect to run-off on Wednesday.
Latent heat of condensation releases 600 calories of heat energy per gram of water to the atmosphere. In this case a combination of orographically forced rising of air and the movement of milder air across the cold, snow will generate latent heat release via condensation in the air and at the surface of the snowpack. Rapid snow melt can occur in such cases.
Some energy; however, is absorbed at the same time, around 80 calories per gram, in the melting process to offset a little of the latent heat that is released with condensation at the snow surface.
Total precipitation in this area has been significantly above locations toward the south in the Tri-Cities, with January 1 to February 5 totals of 5.35″ at the City of Norton WP and between 6.00″ to 7.00″ across the High Knob high country versus 2.57″ measured officially at TRI ( Tri-City Airport ).
This gorgeous photograph by my friend Wayne Riner shows as much snow on the ground across the Apple Orchard as the TRI officially has measured so far during the 2017-18 winter.
Snowfall atop the High Knob Massif has been 10 times greater than down in the TRI just since January 1 ( 30″ versus 3″ ).
Another system with potential to tap into a stronger feed of Gulf Moisture is expected by this weekend so elevated water level concerns may increase in the mountains. It is all part of what is shaping up to be a volatile weather pattern.
Major Changes Across North America
Looking ahead huge changes are underway across the Northern Hemisphere, with a Major Stratospheric Warming Event starting that is currently beginning to stretch out the Polar Vortex ( above ) at top of the stratosphere.
Observe that a downward translation of the above flow pattern would suggest more zonal to even southwesterly flow aloft into the United States. It is, in fact, not uncommon for milder periods to develop in wake of a Major SSW event, initially, prior to major arctic outbreaks following these episodes by a couple weeks.
Note the above pattern could have short-term help…
It should be noted, before I continue on with a discussion of Polar Vortex changes, that the Madden-Julian Oscillation or MJO ( an eastward traveling tropical wave disturbance ) is forecast to leave Phase 7 and to enter Phase 8.
MJO Graphics Courtesy of The Climate Prediction Center.
Observe that Phase 7, the current MJO phase, favors milder than average conditions in the central-eastern USA while Phase 8 favors colder than average temperatures. So any zonal to SW flow initially trying to be forced by changes in the Polar Vortex could be helped in the short-term by MJO Phase 7. By mid-late February; however, if the MJO wave enters Phase 8 then colder conditions will be favored, and IF changes in the Polar Vortex are favorable it could help enhance development of surges of late winter arctic cold.
If the MJO continues to progress from Phase 8 into Phases 1-3 that would be favorable for cold lasting into or through March, since at this time of year those tend to be cold phases for the eastern USA. The bottom line, the MJO alone suggests there is much winter to come and only time will tell if these polar vortex changes will aid or work against the MJO forcing. If both wave forcings from these should align to interfere in a constructive manner, then look out for big time wintry conditions to develop during the second part of February and March. Remember the type of conditions occurring at any given place is due to the summation of all the atmospheric forcings and how they interact with each other ( all are essentially waves such that they can theoretically be thought of as working together to increase amplitude or working against each other to diminish the amplitude, or impact, of any particular pattern ).
Back to the polar vortex changes….
Although the outcome of SSW events are never certain, an increasingly volatile pattern is likely to generate forecast model chaos that translates to headaches for all forecasters during the next couple of weeks as the Polar Vortex splits and warming rotates around the great gyre.
This is currently forecast by the GFS and European models to become a Major SSW ( Sudden Stratospheric Warming ) event, with reversal of winds at 60 degrees North latitude and 10 MB from westerly to easterly ( above ) in direction.
A temperature rise equivalent to 50-70+ degrees F is expected to rapidly occur during the coming week.
Not locally, or at the surface of the North Pole, but aloft where the air is being violently lifted by breaking tropospheric waves which will be breaking and releasing their contained momentum and energy to force dramatic changes in both atmospheric temperatures and wind speeds-directions.
This is expected to span the depth of the Polar Stratosphere with strongest warming forecast to rotate around a main vortex lobe that splits off and moves over North America.
Another way to view these dramatic changes is via a model cross-section of temperature between the Equator and the North Pole, with the current situation ( above ) changing to a much different zonal profile ( below ).
Observe that the temperature change above 70-90 N, centered on 30 to 40 MB, rises by some 40 degrees Celsius ( 72 F degrees ) in the next 10 days ( between above and below graphics ). That is HUGE. Observe also that as the vertical temperature gradient weakens over the North Pole that it increases above Middle Latitudes!
Yet another way to view these changes is by looking at a cross-section of atmospheric winds between the Equator and North Pole ( Northern Hemisphere ).
At the current time ( above ) both the Polar Night Jet over the Arctic and the Polar Front Jet Stream over the Middle Latitude are clearly visible ( both are westerly ).
Compare the current setting ( above ) to the forecast in ten days ( below ), with a shift to deep, strong Easterly winds throughout the vertical depth of the atmosphere over the 70-90 degree North latitude zone. Easterly flow has also developed above 60 N at 10 MB to meet the official WMO criteria for a Major Sudden Stratospheric Warming.
Easterly flow near the surface, associated with the Trade Winds, can also be observed between the Equator and 28 degrees North. In addition, east flow associated with the Quasi-biennial Oscillation can be seen above the Equator ( this is a -QBO winter season ).
So what does this all mean?
It means, at the least, a major atmospheric event is taking shape that will impact weather conditions across all of the Northern Hemisphere through coming weeks.
While an Arctic Outbreak matching historic levels, as was experienced during January 1985, is not likely ( it can not be ruled out ) the odds of having outbreaks of arctic air will be increased by this event for portions of the middle latitudes. The timing and regions of impact are yet to be determined, but it is a wonderful thing to live during a time in which knowledge has advanced enough to understand the potential implications of current changes.
To understand that the troposphere and stratosphere are not disconnected, separated entities that do not influence each other. In fact, this event is being triggered by waves that originated in the troposphere and have propagated upward to the stratosphere where they, much like ocean waves rolling over onto a sandy beach, will break and release their contained momentum and energy to force changes in atmospheric conditions many miles above the surfaces upon which they originated. In turn, these changes in the stratosphere will feedback to generate tropospheric changes ( impacting where you and I live ).
It is, of course, more complicated than what I have written but this captures the big picture idea of what is happening.
*These Sudden Stratospheric Warming Events are a normal part of atmospheric climatology and are not something new, and due to global warming. Only in recent decades has recognition of these events increased enough to begin developing an understanding of how the troposphere and stratosphere can couple in such intimate ways to impact each other and all living things.
ALERT For Hazardous Conditions Developing Overnight Into The Predawn-Morning Hours Of Sunday ( February 4 )
ALERT For Strong SSE-SSW Winds Developing Along Mid-Upper Elevation Mountain Ridges Into Sunday
Another fast moving weather system will begin impacting the mountain region Saturday Night into Sunday Morning, with development of strong winds at mid-upper elevations and lowering cloud bases that will give way initially to snow.
Snow may become heavy before a transition to sleet and freezing rain and rain occurs during Sunday. A change back to snow, with additional accumulation, is expected Sunday Night into Monday morning as air once again turns bitterly cold. Numerous school schedule changes are expected to become necessary for Monday.
Friday Night Into Saturday Morning
Partly-mostly clear through the evening, then increasing high clouds overnight into morning. Bitterly cold. Light winds, becoming WSW-W at 5-10 mph, with higher gusts, along high mountain ridges. Temperatures in the single digits to low 10s, except below zero in colder mountain valleys at upper elevations of the High Knob Massif to Burkes Garden corridor. Sub-zero wind chills on high mountain ridges. Temps tending to rise along upper elevation mountain ridges overnight.
Mostly cloudy ( mid-high clouds ). SSE-SSW winds 5-10 mph, with higher gusts, below 2700 feet. Winds SSW-SW at 5-15 mph, with higher gusts, above 2700 feet. Temps varying from the 20s to near 30 degrees in upper elevations to the mid-upper 30s. Wind chills in the 10s & 20s along higher mountain ridges.
Snowfall Forecast – Two Different Periods
I ). Predawn-Morning Hours Of Sunday
A general 1″-2″ with locally higher amounts possible
This is the most difficult period to forecast since it has HUGE BUST potential, let that be stated CLEARLY with either little to no snow accumulation if warm air advection is fast enough to overcome evaporative cooling and other factors, or with significantly more snow should column cooling trend toward an isothermal vertical profile during the period of heaviest precipitation. I have gone in between these two scenarios, with 1″ to 2″ prior to a transition.
The High Knob Massif and Norton-Wise to Sandy Ridge area is of most concern with a potential to over-achieve, while lower elevations in Powell Valley and farther north into portions of northern Wise-Dickenson-Buchanan counties have the highest potential to under-achieve ( with little to no snow ), especially if winds can penetrate through a low-level inversion which will be trying to develop above the cold, still snow covered ( in many places ) ground.
II ). Sunday Night Into Monday Morning
A general 1″-2″ along the Upslope Side of the mountains with respect to NW flow ( i.e., along and west-northwest of the Cumberland-Allegheny Front ).
This is the easy period of the forecast with upslope snow showers developing as bitter cold air pours back into the mountains during Sunday Night into Monday. This will generate low density, fluffy snow with high snow to water ratios.
Saturday Night Into Sunday Morning
Lowering cloud bases. Becoming windy. Snow developing overnight into the morning, becoming mixed with sleet or changing to rain at lower elevations. Snow may be heavy. SSE-S winds 10-20 mph, with higher gusts, below 2700 feet. S-SW winds 20 to 30+ mph, with higher gusts, on mountain ridges above 2700 ft. Temperatures in the 20s to lower 30s. Wind chills in the 10s and 20s, except single digits possible at highest elevations.
Any snow or mixed precipitation changing to rain. Low clouds and areas of widespread dense fog. Nasty. Winds SSE-SW and shifting to W by late at 5-15 mph with higher gusts. Temperatures mainly in the 30s ( rising into the lower 40s in downslope locations if winds are able to penetrate a low-level inversion. Wind chill factors in the 20s to lower 30s.
Sunday Night Into Monday Morning
Turning bitter cold with rain changing to snow showers. Wind shifting NW at 10-20 mph, with higher gusts. Temps dropping into the 10s to around 20 degrees at low-middle elevations and into single digits at the highest elevations. Dense fog ( clouds ) with riming at upper elevations around and above 3300 feet. Wind chills plunging into the single digits above and below zero, except to colder than -10 F below zero at highest elevations.
February 1-2 Winter Storm Recap
Although a SW upslope flow snow did not develop, a rain-snow mix occurred Thursday afternoon at the summit level of the High Knob Massif prior to a change to heavy snowfall between 6 to 7 PM. A while later heavy snow also developed at UVA-Wise ( above ).
*Reference later notes on why a SW upslope flow snow did not realize its potential, and it was predicted to only be a potential.
This webcam at UVA-Wise is named the High Knob Massif cam since it looks at part of the lofty crest line which rises just south of Wise; however, at this time the massif was still standing amid clouds producing rime and snow.
Ground Depths (Snowfall Totals )
Clintwood: 2″ to 3″ ( 2.3″ at Clintwood 1 W )
Norton-Wise: 2″ to 4″+ ( 3.6″ measured by Layton Gardner )
High Chaparral: 3″ to 5″+ ( 4.5″ measured by Joe & Darlene Fields )
*High Knob-Eagle Knob: 3″ to 12″+ ( 6.0″ of snowfall )
*Note the large snow depth variations at high elevations in the High Knob Massif, with wind driven horizontal snowfall. The actual fall could have been higher than the total estimated.
Can you detect a trend in this data, certainly, a notable increase in snow amounts with increasing elevation.
While that might often be the case, in this event it was especially true due to faster changes to snow at middle to upper elevations versus lower elevations ( below 2K feet ).
A gorgeous conclusion to a bitterly cold winter day featured orographic standing wave clouds illuminated by the setting sun, with flakes of snow still falling in flurry form.
A beautiful array of mountain wave and instability clouds were captured by the daily MODIS pass of the Terra satellite.
My snowfall forecast verified because the system was intense, with good orographic forcing despite its rapid movement.
A couple factors prevented the SW upslope from producing snow. A slow but steady increase in moisture allowed the atmosphere to saturate from the top downward in advance of precipitation to help minimize evaporative cooling + the advection or transport of warm air around and just above 850 MB was just a little stronger than initially forecast; therefore, I only predicted this as being a potential.
It was a very close setting, with snow mixed with rain at the summit level of the High Knob Massif Thursday afternoon prior to an early evening change. Temps at high elevations fell quickly to freezing given they did not have far to drop.
Past climatology shows there is a somewhat higher probability of having SW upslope flow snow events during La Nina winters.
ALERT For Significant Snow Accumulations During Thursday Into Friday – Bitterly Cold Air And Wind Chill Factors Are Expected To Make This A Significant Impact Event In The Mountains
*Many school closings and schedule changes are expected for Friday ( Hey Teachers!!! ).
Significant snowfall is expected during Thursday Night into Friday Morning with a change to snow at all elevations in the 7:00 PM to Midnight period of Thursday evening.
The Potential For A Period Of Snow On SW Upslope Flow Exists For The Locations Indicated Above During Thursday Afternoon Prior To A Change To Snow At All Elevations And Sites Into Thursday Evening
The potential for SW Flow Upslope Snow is being monitored for Thursday in locations along and to the southwest of the orographic lifting zone generated by the High Knob Massif and Tennessee Valley Divide.
Main aspects that could prevent formation of this unique feature of Appalachian Climatology are development of a cross-contour ageostrophic flow that cuts across high terrain to force sinking air over valleys, instead rising, and stronger warm air advection above 850 MB than models indicate.
Locations inside the RED above will be most favored where low-level air will be forced to rise to highest levels, with areas in the black in the potential zone where air rises 1000 vertical feet or more upon valley floors between the Virginia-Tennessee border and the City of Norton.
Wednesday Night Into Thursday Morning
Mid-high clouds. Windy. SSW-SW winds 10-20 mph, with higher gusts, at elevations below 2700 feet. SSW-SW winds 15-30 mph, with higher gusts, along mountain ridges above 2700 feet. Temps varying from 20s in sheltered valleys to the mid-upper 30s. Wind chills in the 20s and 30s, except locally below 20 degrees in stronger gusts on high peaks.
Thursday Morning Through The Afternoon
Increasing & lowering cloud bases with rain, mix, and snow developing. The chance of snow-mix more likely along and southwest of the High Knob Massif-Tennessee Valley Divide, with mix or rain northeast of this corridor. SW-WSW winds 5-15 mph, with higher gusts, at elevations below 3000 feet. SW-W winds at 10-20 mph, with higher gusts, at elevations above 3000 feet. Temperatures in the upper 20s to low-mid 30s, or falling to these levels, except middle to upper 30s in downslope locations ( coldest at highest elevations ). Wind chills in the 20s to lower 30s, except in the 10s at the high elevations in the High Knob Massif.
Thursday Night Into Friday Morning
Rain or a mixture changing to snow. Snow heavy at times. Turning bitterly cold. SW to W winds shifting NW at 10-20 mph with higher gusts. Temperatures plunging into the 10s by morning, with single digits at highest elevations. Wind chills dropping into the single digits above and below zero, except to under -10 degrees F at highest elevations. Rime formation at elevations above 3000 feet.
Preliminary Snowfall Forecast ( Into Friday AM )
2″ to 4″ at elevations below 2500 feet
4″ to 8″ at elevations above 2500 feet
Target Snowfall of 4″ for Norton-Wise ( +/- ) 1″ Error Potential. This suggests a 3″ to 5″ snowfall potential for the Norton-Wise area, with higher amounts likely across the sprawling high country ( above 3000 feet ) in the High Knob Massif.
A potentially more significant winter storm will impact the mountain region this weekend into early next week.
Weather Discussion ( Interesting )
A very interesting, to say the least, weather pattern is now taking shape. Although the next wave arriving by later this weekend will be much stronger, the disturbance impacting the mountain area Thursday into Friday has potential and will have a notable impact even if the rain-snow change does not occur until after sunset Thursday.
From a research perspective the Thursday system will be very interesting to me and has potential to develop snow on a SW upslope flow. Although I have documented these SW upslope snowfall events back into the 1970s, I have a composite chart displaying 925 MB flow during a few “younger” events.
If SW upslope flow snow occurs it will only be for part of this event, with the main snow period being Thursday night into Friday morning. That is generally the case, with only a few events in the past being almost completely dominated by SW upslope flow snowfall. At the least, this type of flow will keep temperatures colder and make for a faster change to snow in the SW upslope flow corridor versus locations under downslope flow on SW winds.
Recent terrain model forecast trajectories are nearly identical, as noted below, but translating that to reality requires the model to be accurate with both flow trajectories and the magnitude of warm air advection around and above 850 MB.
Looking at new 00z data on Wednesday I think that this is trending toward mostly an all snow event for locations in upper elevations of the High Knob Massif, with snow levels during Thursday afternoon prior to the widespread change into all snow ( at all locations ) being the only real question. Places that get snow during the SW flow period will pick up general 1″-3″ amounts; therefore, I have factored that into my preliminary snowfall forecast for upper elevations.
If snow levels should drop to the floor of Powell Valley prior to the main, widespread change to snow then final snowfall amounts in such locations will tend to be near the top, or above, my current forecast ranges.
Meanwhile, I introduce a new weather station courtesy of one of my field research students, Layton Gardner, who graduated with honors from UVA-Wise in Spring 2017.
Layton is currently assisting with the High Knob Project as he prepares to later attend graduate school.
Layton’s station is less than 2 air miles from Lonesome Pine Airport and is about 100 feet higher in elevation. It should not be surprising, of course, that the air temperature runs lower ( I have only talked about this now for YEARS ).
At a slightly higher elevation than the Airport cold air drainage can certainly not be blamed, and since Layton’s station has a small solar radiation shield I highlight current data when incoming and any reflected insolation is not a factor ( on a well mixed night ).
A 4 degree F air temperature difference at current recording times ( note 39 degrees at 8:14 PM versus 43 degrees at 8:15 PM ).
Recap Of The January 29-30 Event
A beautiful Great Lakes connection was featured during the January 29-30 event, with orographic mountain waves even visible on this night image from GOES-16.
Snow depths varied from 1″ at UVA-Wise to 3″ at Layton’s station, only a short distance away, with 2″ measured by Superintendent Andrew Greear at the City of Norton’s Water Plant ( 3.81″ of total precipitation in January ).
Snow depths of 3″ to 5″+ were common at upper elevations across the High Knob Massif and Black Mountain, with 3″ being measured at my station in Clintwood.
ALERT For Moderate To Heavy NW Upslope Flow Snowfall Monday Night Into Mid-Morning Tuesday
A upper air wave and significant moisture transport from the Great Lakes is likely to generate heavy upslope snowfall during Monday Night into Tuesday, especially along & west northwest of the Cumberland Front ( High Knob Massif and Tennessee Valley Divide ).
Locations along the west-northwest side of Clinch Mountain, as well as the secondary lifting zone from Mount Rogers southwest along the Tennessee-North Carolina stateline to the summit level of the Great Smokies are also included; however, the most widespread impacts will occur along and to the northwest of the Cumberland-Allegheny Front. Reference the end of this page for Mesoscale-Synoptic notes.
Bursts of intense snow are expected to reduce visibility and create hazardous driving conditions Monday Night into the overnight of Tuesday. Please use extreme caution.
Cold Air Is Expected Tuesday Into Wednesday Morning
Temperatures are currently expected to drop into the 10s to around 20 degrees on Tuesday Morning, with single digits to around 10 degrees at highest elevations. Wind chills will be significantly lower at mid-upper elevations.
The potential for the coldest temperatures to occur in mountain valleys is being monitored for Tuesday Night into Wednesday AM, with single digits and 10s. Local below zero readings will again be possible within coldest mountain valleys at upper elevations of the High Knob Massif ( especially if snow is on the ground ).
Sunday Night Into Monday Morning
Periods of Drizzle. Dense fog at mid-upper elevations above 2000-2500 ft, then cloud bases lifting at upper elevations. Areas of dense fog possibly developing or reforming at low-middle elevations. NNW-NNE winds 5-10 mph with higher gusts. Temperatures dropping into the 20s to around 30 by morning, coldest upper elevations. Wind chills dropping into the 20s to around 30 degrees, except 10s at highest elevations in gusts. Freezing fog at the highest elevations into overnight prior to clouds lifting.
Monday Morning Through The Afternoon
Low clouds giving way to a mid-high cloud-sun mix before increasing clouds during late afternoon. A chance of snow flurries or sprinkles late. WNW-NW winds 5-15 mph, with higher gusts. Temperatures varying from upper 20s to low 30s at highest elevations to the upper 30s to lower 40s. Wind chills in the 20s and 30s, except 10s high peaks.
Snowfall Forecast Through Mid-Morning Tuesday
2″ to 4″ along and north-northwest of the Cumberland Front, with locally higher amounts, especially at upper elevations within the High Knob Massif. A more narrow zone, along the secondary lifting zone, is expected with similar to somewhat less amounts from Mount Rogers southwest along the TN-NC border to the Smokies.
A dusting up to 1″ in downslope locations along the Powell, Clinch and Holston river valleys ( any bursts here being due to instability aloft and not orographic rise ).
Monday Night Into Mid-Morning Tuesday
Turning colder with snow showers & squalls. Bursts of intense snow. NW winds increasing to 10-20 mph, with higher gusts. Blowing-drifting at high elevations. Temps dropping into the 10s to lower 20s at low-middle elevations along and northwest of the Cumberland Front, with single digits to low 10s at upper elevations. Wind chills in the single digits to low 10s, except 0 to -15 below at upper elevations above 3000 feet. Rime formation at high elevations. Widespread hazardous travel conditions developing across the upslope zone.
Mid-Morning Tuesday Through Tuesday Afternoon
Snow showers & flurries gradually ending. Becoming partly to mostly sunny. Cold. NW winds 5 to 10 mph with higher gusts. Temperatures varying from mid-upper 10s to mid-upper 20s to around 30 degrees ( coldest upper elevations ). Wind chills in the 10s to low 20s, except single digits at highest elevations.
Tuesday Night Into Wednesday Morning
Mostly clear through the evening, then increasing mid-high clouds overnight into morning. Large vertical temperature spreads developing between frigid mountain valleys and rising temperatures on mountain ridges. Light & variable winds becoming SSE-SSW at 5-10 mph on ridges. Temps dropping into single digits & 10s, then rising on mountain ridges into the 20s overnight into morning. Local below zero temperatures possible in upper elevation valleys.
The potential for more heavy snow is being watched for the February 1-2 period, with additional waves expected to bring more snow by February 4-5 and beyond into next week. A very snowy period is upcoming for the mountain area.
Weather Discussion ( Very Active )
A very active ( energetic ) winter pattern will be returning to dominate the mountain landscape through coming days.
The initial priority features low cloud bases, drizzle, and dense fog through Sunday Night into Monday on northerly upslope flow and dropping temperatures.
A short break during Monday will feature a dissipation of low clouds as mid-high clouds appear overhead to signal the next weather system rapidly approaching. An increase in clouds will occur later Monday as bases begin to drop once more on increasing NW upslope flow.
Prime conditions develop Monday Night into Tuesday for snow showers & squalls. I expect heavy snow with intense bursts of whiteout type snowfall at times to greatly drop visibility and create hazardous driving conditions.
*There are likely to be many school delays and cancellations by Tuesday morning, especially in counties along and west of the Cumberland-Allegheny Front.
Good orographic forcing will be aided by steepening lapse rates and a passing upper wave to really help intensify the snow showers into squalls. For those unaware, this setting could really catch them off-guard so be warned now if you have travel plans Monday Night into Tuesday Morning.
Albedo will make certain that Tuesday is a cold day with continuation of low sun angles once the snow showers and flurries end and low clouds break. A rather classic setting follows into Tuesday Night with light winds and a plummet in temperatures over snow cover through the evening, this will be enhanced by warm advection aloft with a strong temperature inversion forming above valleys.
A couple examples, of many, from January 2018 of rapid evening temperature drops analogous to what is expected Tuesday evening in high valleys of the High Knob Massif are cited here ( with strong drops in all valleys, these just being part of our high country mesonet ).
Reference my 010618 Forecast in the “Previous Discussion” section to review the above period of time as I was forecasting it to occur. The above data was downloaded during a January 27 Field Trip with research students from UVA-Wise.
At Midnight on January 7 the temp was -8.4 degrees Fahrenheit below zero, with the following regional temperatures reported at the same time courtesy of the WCYB-TV 5 archive.
Beyond Wednesday the main focus will be on upstream waves in the jet stream that will threaten the mountain region with a potential winter storm. Right now it remains only a potential, but the totality of ensemble guidance from the European group suggests that a threat is justified. This should become clear by mid-week, so stay tuned.
The following was written Monday afternoon-early evening, then an internet outage prevented posting until near Midnight on January 29.
Mesoscale-Synoptic Forecast Notes – January 29
From my perspective this was the easiest winter forecast of the season, as it was very clear as to the result. That is far from being true regarding numerous NW flow settings in the southern Appalachians, with the main difficulty being marginal Great Lake air flow trajectories ( which can be calculated in reverse during and after events ).
11:00 PM Update: 2″ to 3″ of snow is on the ground at my official station in Clintwood. This snow was due to the cold frontal band and upper wave. Now the Great Lake moisture follows to continue snow into sunrise to mid-morning Tuesday when dry air will surge into the region to dissipate low-level moisture.
Remember, of course, my elevation is 1560 feet above mean sea level or just a bit higher than Tri-City Airport. The main difference being this location is embedded within the initial lifting zone with respect to NW flow trajectories, the main emphasis of these notes.
It is important to note that my use of terrain features is based upon 30 years of research, during which time the collection of data has demonstrated that the concept of lift should be applied in respect to orographic forcing based on which lifting zone should receive the most emphasis under what atmospheric conditions.
In the middle, bursts of snow, like observed in the Great Valley during this event tend to be dynamically supported via steep lapse rates and/or upper divergence and cyclonic vorticity advection. Once that departs the Great Valley is subjected to inverse forcing, which from an orographic viewpoint = downsloping to be overly simple.
These notes; however, are about orographic forcing and the primary and secondary lifting zones which it generates and some concepts that forecasters need to apply.
It is generally understood, for example, by forecasters that SE air flow streaming into the Blue Ridge generates heavier precipitation along the Blue Ridge escarpment versus more interior locations along the Blue Ridge ( Mount Mitchell and Grandfather Mountain tend to get more than mountains on a northeast-southwest transect through Mount LeConte on this type of flow, and Meadows of Dan tends to get more than Whitetop Mountain ).
Even through Meadows of Dan is significantly lower in elevation than Whitetop Mountain, the initial lifting of moist air along the flank of the Blue Ridge generates the heaviest precipitation on SE air flow trajectories in the MEAN ( there always can be exceptions during any particular weather event ). This is also the reason that southwestern North Carolina contains the wettest terrain in the southern-central Appalachians since it is situated in a position to obtain initial lifting of inflow from both the Gulf of Mexico as well as the Atlantic Ocean ( total mean annual precipitation tending to decrease with increasing distance from the zone of initial lift due in large part to increasing moisture extraction by orographics that force repeated rises and sinking of air along a flow trajectory ).
The Blue Ridge ( and especially its escarpment ) is the primary lifting zone with respect to SE flow trajectories. Leeward sinking generates an enhanced minimum in total precipitation along the Great Valley corridor, followed by an increase in amounts again along the secondary lifting zone of the Cumberland-Allegheny Front on SE flow.
The secondary lifting zone produces less total precip than the primary lifting zone, due in part to mountains being lower in mean elevation but also due to upstream moisture extraction along the primary lifting zone = less total moisture within a vertical column of the atmosphere to be precipitated out ( * ).
*While this is generally true, I have identified a unique winter circulation that appears indigenous to the High Knob Massif which greatly enhances snowfall on SE air flow trajectories under specific conditions. But that is not what these notes are about.
Flip this to NW flow. Since NW flow during winter is often cold, only snowfall will be considered. During NW flow the primary lifting zone is formed by those mountains & their adjacent foothills which are along & west of the southeast flank of the Cumberland-Allegheny Front.
During NW flow the Cumberland-Allegheny Front becomes the focus of the primary orographic lifting, and in the mean the greatest snow amounts with initial lifting ( the towns of Wise and Clintwood, for example, have higher annual snow totals than Big Meadows at the top of Shenandoah National Park even though they are much lower in elevation ).
Shenandoah National Park reports that 43 cm ( 37.0″ ) of snow falls annually in Big Meadows at 3500 feet above mean sea level versus around 112 cm ( 44″ ) at 1560 feet elevation in Clintwood, and up to 196-274 cm ( 77-108″ ) in the 3200-4200 foot elevation zone of the High Knob Massif. Granted all air flow trajectories comprise mean annual snowfall totals, but a significant amount of the annual tally is comprised of NW flow snow and even more is associated with air flow trajectories having westerly components.
A major, major problem in past decades were models that always tended to “model” heaviest snow toward the ECD, or Eastern Continental Divide, on NW Flow snow and most other flow trajectories ( the ”horseshoe” pattern that now shows up well in modeling around the Great Valley was not present during past decades ). Although model resolution has improved, it is still lacking in part because elevation remains a controlling factor + models can not understand or parameterize the initial lifting concept with still poor resolution of important complex terrain features ( ** ).
**This remains a major factor for the Cumberland Front more so than the Allegheny Front, since it becomes part of the Eastern Continental Divide at the latitude of central-northern West Virginia + there are many more NWS Cooperative stations at elevations above 3000 feet which are used as data inputs.
Although much terrain is above 3000 feet along the Cumberland Front, no stations are officially inputting any data into modeling now that the Black Mountain Cooperative has closed.
So initial lifting during NW Flow snowfall events continues to be under-estimated by both models and forecasters, with too much emphasis consistently placed upon what is the secondary lifting zone ( Blue Ridge ) in this type of flow.
I applaud Baker Perry & Charles Konrad for highlighting this fact years ago, yet it seemed to make little difference in the general forecast community to again exemplify the hole of disconnect that exists between operational forecasters in private, commercial and government sectors with those in the field doing on the ground research.
Even this above graphic is MUCH under-estimated since it incorporates no data from the snowiest mountain mass in Virginia where model errors on snowfall of all trajectories, but certainly on the NW Flow snowfall events, are much more than 30.5 cm listed for the Wise NWS Cooperative.
Wise tends to receive 40-60% less snow than upper elevations in the High Knob Massif, which is obvious to anyone in this area who may live or visit the area. Many residents live above 3000 feet on both the Wise & Scott County side of the high country. Leaving the portion in Scott County consistly out of most winter advisories is another problem that needs addressing ( it could be solved easily by joining that portion of Scott County north of the Clinch River with Wise County in winter weather settings such as NW flow ).
Moisture extraction along the initial lifting zone of the Cumberland-Allegheny Front on NW Flow snowfall means there is less moisture in a vertical atmospheric column to be precipitated out along the secondary lifting zone of the Blue Ridge, such that air has to be lifted to higher elevations in order to achieve as much snowfall. That is why it is nearly impossible, if not impossible, to find locations along the Blue Ridge where 75-100″+ of snowfall occurs annually at elevations as low as 3000 to 4200 feet ( *** ).
***Mount LeConte, at 6400 feet above mean sea level, at the summit level of the Great Smokies, on the windward side of the mountain range, has an annual snowfall average of around 100″ .
When Great Lake moisture transport into the initial lifting zone is vertically shallow in nature then it is impossible in many cases, regardless of elevation along the Blue Ridge, to achieve as much snowfall as on the Cumberland-Allegheny Front. If moisture transport is deeper; however, and also if orographic forcing is moderate-strong + upper dynamics are also favorable, then snow amounts reported at higher elevations along the Blue Ridge can match or occasionally exceed those at lower elevations along the Cumberland-Allegheny Front. This is especially true for peaks standing along the front of the Blue Ridge, such as Roan Mountain and Mount LeConte.
For forecast purposes, in particular, forecasters remain too limited and under-estimate the amount and coverage of NW flow snowfall along & west of the Cumberland Front as such events produce widespread accumulations ( # ). While this is of course partly due to a continued need for better terrain resolution by forecast models, it is also due to a fact that despite decades of forecasting and recorded climatology there never seems to be the needed adjustments.
#The widespread snow having enhancements with superposition of snow squalls and snow streaks developing in the 925 to 850 MB flow field to add to the widespread coverage. Leeward of initial lifting, coverage of accumulating snowfall is typically hit or miss and too often this hit-miss nature that is so common in downslope locations ( like the Great Valley ) is applied to the primary lifting zone in forecasts ( when only heavier local amounts should be stressed upon an otherwise widespread accumulation ).
The main focus from my perspective as both a researcher and teacher is this most important fact…the human brain remains the superior forecasting tool and is often forgotten with too much emphasis being placed upon computer model output, statistics, fancy graphics, and zone forecasts. Each forecaster should ideally make their own personal forecast from scratch, using raw model data and past climatology of analogous events, and if it then agrees with other forecast sources then that is great. In other words, do away with copy, slightly adjust, and paste!
An ALERT Continues For Strong-Gusty SSE-SW Winds During Monday Night Into Tuesday Morning As Temps Begin To Turn Colder. The Coldest Air Is Expected To Arrive Tuesday Night Into Wednesday.
A general SSE-S wind flow and mild conditions will continue through Monday evening, with highest elevations and favored mountain wave zones having the strongest wind speeds. Local gusts over 50 mph will be possible.
A wind shift to SW overnight is expected to begin to focus the strongest winds into the Wise & Sandy Ridge plateaus and upper elevations of the High Knob Massif during the predawn to mid-morning period Tuesday, with general strong-gusty conditions across the area in a widespread nature along and behind the passage of a cold front. Air temperatures Tuesday will display falling trends during mid-late afternoon, following any small rises or steady nature through early Tuesday PM.
Cold air will surge into the mountains Tuesday night into Wednesday with enough low-level moisture to generate some snow showers, flurries, and a chance for local squalls.
Monday Night Into Tuesday Morning
Mostly cloudy and mild through the evening with a chance of rain showers. Rain showers becoming likely overnight. A chance of thunder. Turning chilly by morning. Windy. SSE to S winds shifting SW at 10-20 mph, with higher gusts below 2700 feet. Winds SSE to SW at 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures dropping into the low 30s to low 40s by morning ( coldest at highest elevations ). Wind chills dropping into the 20s to low 30s, except 10s at the highest elevations, by morning.
Tuesday Morning Through The Afternoon
Predawn to mid-morning clearing giving way to cloudy skies. Turning colder. Gusty. A chance of flurries by late. SW to W winds 10-20 mph with higher gusts. Temps near steady to falling into the 20s at upper elevations and into the 30s at lower-middle elevations along and north to west of the High Knob Massif-Tennessee Valley Divide. A little milder in downslope locations of the Clinch, Powell, and Holston river valleys. Wind chills in the 10s and 20s, coldest at highest elevations.
Snowfall Forecast – General dusting up to 1″ between Tuesday Night & Midnight Wednesday ( locally more possible at upper elevations of the High Knob Massif )
Tuesday Night Into Wednesday Morning
Snow showers & flurries developing late into overnight. Light snow accumulations. Cold. W-WNW winds 5-15 mph, with higher gusts. Temps varying from the middle-upper 10s to the middle-upper 20s ( coldest at upper elevations ). Low cloud bases with rime formation becoming possible at highest elevations. Wind chill factors dropping into the 10s to low 20s, except single digits to around 0 degrees in gusts on highest mountain ridges.
Wednesday Morning Through The Afternoon
Partly-mostly cloudy. A chance of snow showers, flurries. Light accumulations possible. Cold & blustery. WNW winds 5 to 15 mph with higher gusts. Temperatures varying from upper 10s to lower 20s at upper elevations to upper 20s to lower 30s at low-mid elevations along and north to west of the High Knob Massif-Tennessee Valley Divide. Wind chills in 10s to low 20s, except colder on highest peaks.
Wednesday Night Into Thursday Morning
Partly-mostly cloudy. A chance of flurries. A heavier local snow shower possible during the evening. WNW winds 5-15 mph, with higher gusts. Temperatures widespread in the 20s and 10s ( coldest at upper elevations ). Wind chills in the 10s and single digits ( below zero in gusts on highest peaks above 3500 feet ).
The potential for a significant storm system featuring a rain to snow transition is being monitored for the late weekend-early week period of January 28-29. Stay tuned for updates.
Reference January 1985 Arctic Blast for a review of a great cold wave that froze the mountain landscape 33 years ago this week.
Weather Discussion ( Up-Down Pattern )
January 23 Update
This update is to include light snow accumulations with activity developing late Tuesday night into Wednesday, amid limited moisture, and to slightly adjust temps.
A little blush of color on clouds that increased during Tuesday afternoon to cap off a very windy period.
As expected, the strongest winds developed in the Wise area as low-level winds shifted SW overnight into Tuesday with gusts topping 40 mph. A peak gust of 52 mph was recorded by the Black Mountain Mesonet, with no doubt higher gusts in open meadows from the High Knob peak to Camp Rock.
*The Camp Rock Meadow ( a quarter to one-half mile long ) is often very windy on air flows possessing both southern components and northerly components ( elevation around 3900 feet ).
Temperatures reached a mid-morning MIN then climbed amid sunshine to a early afternoon MAX before slowly beginning a decline during mid-late afternoon.
*The MAX temp for the day occurring just after Midnight.
Although moisture is limited with incoming continental Polar air, given Great Lake moisture injection is missing the southern Appalachians toward the north, a couple of upper air waves in the flow field will combine with WNW upslope to generate snow showers and flurries. A heavier burst of snow, on at least a localized basis, can not be ruled out.
Most of the activity is expected overnight into Wednesday morning with the initial cold air advection and developing WNW upslope, then again late Wednesday with a stronger upper air wave and 850 MB thermal MIN.
*I expected the heaviest snow to fall in the area of Canaan Mountain and Canaan Valley in the northern mountains of West Virginia, with totals of more than 6″ being possible there into Thursday AM.
A up-down temperature regime is expected to rule the remainder of January 2018, with increasing signs that another prolonged wintry lock-down will develop during February across the eastern USA. Could the worst of this 2017-18 winter season be upcoming?
Frequent mountain waves were observed through Monday as strong winds blew across the High Knob Massif ( below ).
Although most mid-upper elevations locations were in the 50s during Monday, temperatures varied from upper 40s at the summit level of the High Knob Massif to middle 60s in downslope locations like Clintwood ( 64 degree PM MAX ).
Strong low pressure over the center of the nation began to impact the mountains Monday, with gusty winds and a mild flow of southerly air ( it is difficult to get a truly warm feel to the air at the top of the high country in January, with 40s and wind gusts over 30 mph, but compared to last week it was a ”balmy” day with modified maritime tropical air mass advection ongoing in advance of a cold front ).
Showers, with embedded thunder, are developing in the warm sector of the current cyclonic storm where warm conveyor belt air is being lifted ahead of the system’s cold front and its descending dry conveyor belt air which is sinking downward from the mid-upper troposphere to generate a dry slot that is visible on satellite imagery.
Thunderstorms developing in the warm sector west of the mountains are forming in a Theta-E ridge, or low-level axis of available potential energy, which is forecast to fade as activity propagates east into the mountains, thus I have only a chance of thunder as the front approaches.
Observe the large swirl of the current cyclone dominates this view of North America, with a pronounced comma-head of low clouds in its cold conveyor belt that have risen beneath the warm conveyor belt into middle portions of the troposphere and wrapped cyclonically around the center of low pressure.
A pronounced dry slot and warm conveyor belt ( with a Pacific-Gulf of Mexico moisture tap carrying deeper moisture south and east of the Appalachians ) are also clearly visible.
Due to the large, cyclonic circulation around this system air will be turning cold on SW winds as it begins to pull a mass of air featuring continental Polar properties into the area during the predawn-morning hours of Tuesday.
Note that while this is different from the continental Arctic air mass of last week, a rather dramatic change will still occur with falling temperatures & wind chills Tuesday into Wednesday.
Enough low-level moisture will be present to generate snow showers, flurries, and the chance for some local squalls as cold air increases Tuesday Night-Wednesday.
With the best low-level moisture currently expected to flow into the central-northern highlands of West Virginia, that is where the greatest snowfall amounts will likely occur.
A WNW flow field will favor heaviest amounts along and west of the Cumberland-Allegheny Front, as well as within a narrow zone from Mount Rogers southwest along highest elevations of the Tennessee-North Carolina border. Lifting will be aided by passage of a couple upper air waves, such that amounts of 1-2″ will be at least locally possible in the southern Appalachians ( stay tuned for updates ).
Increased wave forcing into the stratosphere, with warmth building above Siberia expected to move across the Pole to above Alaska and western Canada, will aid the rebuilding of tropospheric ridging upstream of the eastern USA during the next 1-2 weeks.
Looking down the rocky road, it appears that much more significant cold air will return to the eastern USA with a variety of factors beginning to come into alignment.
A changing SOI ( Southern Oscillation Index ) with an eastward propagating Madden-Julian Oscillation wave is forecast to enter cold phases for the eastern USA.
It is looking like some very interesting weather times are upcoming as this 2017-18 winter season is not even close to being finished ( with respect to cold and snow ).
Strong SSE-SSW Winds Will Be Developing By Late Monday Into Monday Night As The Next Weather System Arrives With Colder Air & Falling Temps Expected During Tuesday ( January 23 )
Remain Alert For Possible Black Ice From Refreezing
Strong & gusty winds will continue to generate notable wind chills along mountain ridges and plateaus through Saturday, with low cloud formation likely along and to southwest of the High Knob Massif and Tennessee Valley Divide enhancing chilly conditions ( general cloudiness across the remainder of the area with possible downslope breaks northeast of the high terrain ).
Overnight Into Saturday Morning
Increasing clouds overnight into morning. Windy along mountain ridges & exposed plateaus. SW winds 8-18 mph, with higher gusts, at elevations below 2700 feet. Winds SW at 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures varying from 10s in colder valleys to the lower 30s, with valley temps tending to rise toward morning. Wind chills in the 10s and 20s.
Saturday Morning Through The Afternoon
Mostly cloudy. Chilly. Downslope breaks in northern portions of Wise-Dickenson and Buchanan counties. SW winds 10-20 mph with higher gusts below 2700 feet. WSW-WNW winds 10-25 mph, with higher gusts, at elevations above 2700 feet. Temperatures in the 30s to mid 40s. Wind chill factors in the 20s & 30s ( coldest at upper elevations ).
Saturday Night Into Sunday Morning
Partly to mostly cloudy. Winds SW-W at 5-15 mph, with higher gusts, mid-upper elevation mountain ridges and exposed plateaus. Temperatures in the 20s in sheltered mountain valleys versus near steady or slowing rising in the 30s to low-mid 40s on mountain ridges. Wind chills in the 20s & 30s, coldest at the upper elevations.
Partly to mostly cloudy. Winds S-WSW at 5-15 mph, with higher gusts. Temperatures varying from the low-mid 40s to the low-middle 50s. Wind chills in the 30s along upper elevation mountain ridges.
Sunday Night Into Monday Morning
Partly to mostly cloudy. SSE-S winds 5-15 mph on mountain ridges-plateaus below 3000 feet. S-SW winds 5-15 mph with higher gusts at upper elevations. Temperatures from 20s to low 30s in colder valleys to the 40s on mid-upper elevation mountain ridges-exposed plateaus.
Mostly cloudy & windy. SSE-S winds 10-20 mph, with higher gusts, below 2700 feet. S-SSW winds 20-30 mph, with gusts 40-50+ mph, at elevations above 2700 feet. Temps varying from 40s at highest elevations to the mid-upper 50s.
Weather Discussion ( Slow Warming )
Saturday Aftenoon Update
I updated for removal of drizzle chances this afternoon, leaving in a small chance for tonight with air not far from being saturated at high elevations.
Temperatures have mainly climbed into the 40 to 45 degree range, amid gusty S-SW winds.
The January 20 MODIS satellite image did capture cloud breaks across portions of Dickenson-Buchanan counties and into adjacent counties.
Low sun angles ( 32 degree solar angle in Wise on Jan 19 ) and snow cover impacted air temperatures Friday and will continue to do the same through Saturday, with strong and gusty winds at mid-upper elevations adding to the chill.
Although much milder than the peak of recent bitter cold, air remained chilly on the Campus of UVA-Wise Friday with notable chill factors being created by gusty SW winds.
Several interesting features on the MODIS Terra image for January 19, with widespread snow cover remaining from the Piedmont of North Carolina and Virginia across the Appalachians into the Midwest, and a deck of low clouds creeping up the lower Mississippi Valley.
If low-level moisture over the lower Mississippi Valley is lifted up over the mountains into Saturday it will really keep the lid on air temperatures, with best odds of this happening being where the low-level SW flow rises beneath the 850 MB field. Temperatures may struggle to get above freezing atop the high country during Saturday, such that any travel along Route 619, 238, 237, 704, to note a few, should be done with caution.
Friday afternoon MAXS varied from the low 30s atop the High Knob Massif to 43 degrees in Clintwood; although, most middle to upper elevation locales felt significantly colder with gusty SW winds.
SW winds are really cranking tonight at mid-upper elevations and are at a threshold where an alert should actually be issued, but I have them headlined at the top.
When factoring in the frequent gusts, conditions continue to feel like the 10s at high elevations and low-mid 20s in Wise. Sheltered mountain valleys are just cold with calm conditions ( 17.6 degrees in Clintwood as of 12:50 AM Saturday ).
The Bottom Line…Gusty winds, low sun angles, and increasing low-level moisture over lingering snow cover will all be working against warming to keep conditions chillier than models indicate, with the most aggressive warming likely Sunday PM into Monday ahead of colder air returning by Monday Night into Tuesday.
If Winter 2017-18 is truly destined to become one of the great cold winters then settings like this will be rather common, with models generating head-fakes for those who bite and warm periods which end up being shorter than models forecast.
Although it appears that winter returns with a real vengeance into February, this can not yet be known for certain. Seasonal snowfall continues to run well below average, so lovers of snow are hoping that the biggest falls of snow are yet to come ( as have often been observed during February-March and even April ). Time will tell.