Category Archives: 2018 02 Forecasts

My February 2018 Forecast Archive

021719 Forecast

Mountain Area Forecast ( Feb 17-19 )

ALERT For High Water Levels Through Saturday Night Into Early Sunday

Big Stony Creek of High Knob Massif At 8 PM Saturday – February 17
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″ ).

Previous Alert

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.

Reference Late Winter In The High Knob Massif for more details.

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!

High Knob Massif Webcam – University Of Virginia’s College At Wise

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.

NAM 12 KM Model Total Precipitation Forecast

Forecast models are again converging upon this area once more for the heaviest rainfall amounts through Saturday.

NAM 3 KM Model Total Precipitation Forecast

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.
GFS Model Total Precipitation Forecast

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:

Mid-level Water Vapor Image At 10:15 PM on February 16, 2018

This shows up well on the current ( as of Midnight Feb 17 ) streamline flow fields at 700 to 500 MB across the Earth:

700 MB Streamline Flow

500 MB Streamline Flow

 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 ).

European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5

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.

European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10

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 ).

021418 Forecast

Mountain Area Forecast ( Feb 14-17 )

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.

Large Region of Significant Rainfall Possible During Next 7 Days
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.
Former ALERT

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. 

Reference Late Winter In The High Knob Massif for more details.

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.

NAM 12 KM Model Total Precipitation Next 60 Hours

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 ).

GFS Model Total Precipitation Forecast Next 60 Hours

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?

High Knob Massif Webcam – University Of Virginia’s College At Wise

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.
Simplistic AMS Glossary Definition
High Knob Massif Webcam – University Of Virginia’s College At Wise

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.

GFS Model Rainfall During The Next 2 Weeks

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.

European 51-Member Ensemble Mean 500 MB Height Anomalies ( Feb 19-23 )

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.


Previous Discussion

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.

General Rainfall Pattern During Next 5-7 Days

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.
GFS Model Total Rainfall Forecast During Next 5 Days

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 ).

European Model 850 MB Wind Analysis At 7 PM Tuesday – February 13, 2018

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 ).

GOES-16 Low-Level Water Vapor At 3:15 AM on February 14, 2018

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.

Live Surface Flow View

Live 500 MB Flow View

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.

020918 Forecast

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.

High Knob Massif Webcam – University Of Virginia’s College At Wise
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:
Layton Gardner Weather Station – Elevation 2780 feet – Wise Plateau
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 )

Reference Late Winter In The High Knob Massif for more.
*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 ).

*Sphagnum can soak up to 25+ times it weight in water and over acres of land that = a great amount of water storage.  Reference Sphagnum Moss from the Encyclopedia of Life.

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 ).

Tuesday Afternoon

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. 
HRRR Model Future Rainfall Forecast Next 15-Hours – Ending 2 PM Sunday

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! ).

Black Mountain Mesonet At 11:55 PM on February 10

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.

Composite Doppler Showing Training Rainfall

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.

South Fork of Powell At 6:30 PM on February 9, 2018 ( After Sunset )

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

NOAA Weather Prediction Center Rainfall During Next 7-Days
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

Kendall Morse & Kyle Hill – High Knob Massif At 3:26 PM on Friday – February 9, 2018

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 ).
Big Stony Creek of High Knob Massif – February 1-9 History
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.
Lingering Snowpack Along State Route 619 ( Holding 1-2″ of Water Content )

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

NAM 12 KM Model Total Rainfall Next 48-Hours ( To 1 AM Monday )
NAM 3 KM Terrain Model Total Rainfall Forecast Next 48-Hours

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 ).

GFS Model Total Rainfall Forecast Next 48-Hours ( To 7 PM Sunday Feb 11 )

020518 Forecast

Mountain Area Forecast ( Feb 5-8 )

Current ALERTS

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 )

Big Stony Creek of High Knob Massif

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

Eagle Knob of High Knob Massif At 5:03 PM on Tuesday – February 6, 2018
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.

Former Alert

 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.

Tuesday Afternoon

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

High Knob Massif Webcam – University Of Virginia’s College At Wise

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.


Former Discussion

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.

Heavy Snow – Eagle Knob of High Knob Massif at 5:53 AM on February 4, 2018

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.
Heavy Snow & ROARING SW Winds at 8:30 AM on February 4, 2018

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 ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
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!!! ). 
Eagle Knob of High Knob Massif At 10:42 AM on February 5, 2018

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 ).

NAM 3 KM Model Total Precipitation Forecast – Next 48 Hours

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 ).

Long Ridge Orchard At 10:58 AM on February 2, 2018
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

European Model 10 MB Analysis At 7 AM on February 5, 2018

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.

European Model 10 MB Forecast At 7 AM on February 15, 2018
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…

European Model Madden-Julian Oscillation ( MJO ) Forecast – CPC

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.

Composite of MJO Impacts On USA Temps By Phase During January-March
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.

Zonal Mean Zonal Wind At 60 North and 10 MB

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.

Temperatures Above The North Pole At 10 MB

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.
Temperatures At 100 MB Above The North Pole

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.

European Model Zonal Mean Temperature Analysis – 7 AM February 5, 2018

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!
European Model Zonal Mean Temp Cross-Section Forecast – 7 AM Feb 15

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 ).

European Model Zonal Mean Wind Analysis At 7 AM on February 5, 2018

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 ).
European Model Zonal Mean Wind Forecast At 7 AM February 15, 2018

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.

Historic Arctic Outbreak Of January 1985

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.

020218 Forecast

Mountain Area Forecast ( Feb 2-4 )

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.

Saturday Afternoon

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.

Sunday Afternoon

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

High Knob Massif Webcam – University Of Virginia’s College At Wise ( Heavy Snow )

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.
High Knob Massif Webcam – University Of Virginia’s College At Wise

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.
Eagle Knob of High Knob Massif At 7:44 AM Friday ( 8 degrees – Gusty N winds )

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 ).

High Knob Massif Webcam – University Of Virginia’s College At Wise

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.

Eagle Knob of High Knob Massif At 5:50 PM ( Feb 2 ) – Elevation 4196 Feet

A beautiful array of mountain wave and instability clouds were captured by the daily MODIS pass of the Terra satellite.

MODIS Terra Satellite Image on February 2, 2018

My snowfall forecast verified because the system was intense, with good orographic forcing despite its rapid movement.

NAM Model Forecast Sounding For February 1 at 4:00 PM

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.

Actual Initialized Atmospheric Sounding At 1:00 PM on February 1, 2018

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.