Cloudy then becoming partly cloudy by morning. Winds W-NW at 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures dropping into the 40s-low 50s by morning. Local areas of valley fog.
Mostly sunny. Pleasant. Winds becoming westerly less than 10 mph. Temperatures varying from upper 50s to lower 60s in upper elevations to upper 60s to lower 70s.
Friday Night Into Saturday Morning
Mostly clear. Large vertical temperature spread developing between colder valleys & milder mountain ridges-plateaus. SSW-WSW winds 5-10 mph, with some higher gusts, along middle-upper elevation mountain ridges. Temperatures varying from 30-35 degrees in colder valleys to the lower-middle 50s on exposed ridges. Areas of valley frost & fog.
Sunny & unseasonably warm. SSW-WSW winds 5-10 mph, with some higher gusts. Temperatures varying from the mid-upper 60s in upper elevations to the mid-upper 70s.
Saturday Night Into Sunday Morning
Partly-mostly clear ( some high clouds ). Winds SW-W 5-15 mph, with higher gusts, along mid-upper elevation ridges and plateaus. Temperatures varying from the upper 30s to lower 40s in colder valleys to the mid-upper 50s.
Partly-mostly sunny. Unseasonably warm. Winds SW-W at 5-10 mph, with some higher gusts. Temperatures varying from mid-upper 60s in upper elevations to mid-upper 70s.
Weather Discussion ( Dry Pattern )
A dry autumn pattern will continue to grip the mountain region through at least the next week, with a return to the unseasonable warmth experienced during much of October.
With 1.27″ of moisture officially recorded at the City of Norton Water Plant this looks to end as the 2nd driest October on record behind the 0.55″ measured in October 2000.
Around 2.50″ of total precipitation has fallen at the summit level of the High Knob Massif during October. Much below average and a simply huge difference from the 7.00″ to 10.00″ observed during the past two October’s ( in 2014 and 2015 ).
This will likely also end as the 2nd driest October on record in Clintwood where the 0.78″ measured is behind the 0.33″ observed during October 2000 ( records date back 50+ years to 1964 ).
This is clearly short-term dryness for the High Knob Massif area where Summer 2016 was wet. The past two months featuring much below average rainfall.
That is around –3.50” below average for this time of year.
Precipitation so far this year in the City of Norton is already above 2007 ( 39.69″ ) and 1999 ( 42.44″ ), the two driest years on record since recording began in 1983.
This does not ease the dryness now, which is likely to worsen some during the next 7-10 days heading through most of the first week in November.
Decreasing sun angles, especially in the mountains, at this time of year helps reduce evaporation rates, but continued unseasonable warmth will work to partly offset this.
A trend toward colder, wetter conditions is being shown by the latest European Weeklies for the mid-late portion of the new month of November. This has been a period that I have targeted for a while ( mid-November ) now as being the time period when the orographic forcing season would begin to exert a notable influence upon the mountain region ( this will, of course, be dependent upon the synoptic pattern changing from that presently observed ).
Frost Formation Is Expected In Colder Mountain Valleys Into Tuesday Morning. Heavy Frost With A Hard Freeze Will Occur In The Colder Valleys Into Wednesday Morning.
Strong ( Roaring ) SW Winds Are Expected To Develop Wednesday Night Into Thursday Morning Across Mid To Upper Elevation Mountain Ridges-Plateaus.
Overnight Into Tuesday Morning
Clear & colder. Frost developing in colder mountain valleys. Areas of fog along main rivers, lakes, and wetlands. Winds NNW-NE at 5-10 mph, with some higher gusts, along middle to upper elevation mountain ridges. Temperatures varying from upper 20s to lower 30s in colder valleys of the upper elevations to the middle 30s to around 40 degrees.
Partly-mostly sunny ( some high clouds possible ). Light NE-ENE winds. Temperatures varying from upper 40s to lower 50s in the upper elevations to upper 50s to lower to middle 60s ( warmer south into the Great Valley ).
Tuesday Night Into Wednesday Morning
Mostly clear. Cold. Large vertical temperature spread between frosty valleys and exposed ridges. Hard freeze within the colder valleys. Winds SSE-SSW 5-10 mph, with higher gusts, on mid-upper elevation ridges. Temps from lower-middle 20s in colder valleys of upper elevations to the upper 30s to lower 40s on exposed ridges.
Mostly sunny. Winds SSW-SW 5-15 mph, with higher gusts on mountain ridges. Temperatures varying from upper 50s to lower 60s in upper elevations to upper 60s to lower 70s.
Wednesday Night Into Thursday Morning
Becoming cloudy & windy. Chance of a sprinkle or shower by morning. SSW-SW winds increasing to 10-20 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet. Winds SW to WSW at 15-25 mph, with higher gusts, along mountain ridges above 2700 feet. Temperatures in the 40s to lower 50s in valleys to the mid-upper 50s on exposed ridges-plateaus.
Partly-mostly cloudy. Warm. Chance of sprinkles or a shower. Winds SW-WSW 5-15 mph, with higher gusts. Temperatures varying from upper 50s to lower 60s in upper elevations to the upper 60s to lower 70s.
Weather Discussion ( Typical October )
A more typical October weather pattern has been ruling the mountain landscape in recent days, following anomalously warm conditions last week.
It is beginning to look like late autumn-early winter on high valley floors in the High Knob Massif where a hard weekend freeze occurred ( with the first snowflakes of the season at the summit level around High Knob ).
Some 12-13 consecutive hours at or below freezing were recorded during October 22-23 on high valley floors ( from around 9:30 PM on October 22 to after 10:00 AM on October 23 ). This generated a hard freeze due to the long duration ( 9-10 hours in upper 20s ).
Colder valleys in lower-middle elevations also had a rather long sub-freezing period, with 6.5 hours at or below 32 degrees being recorded at the official Clintwood 1 W NWS Cooperative site.
Dry air advection, especially in the 925-850 MB level, will be key to cold nights into Tuesday-Wednesday mornings in the mountain valleys. Especially those in terrain high enough to tap into the really dry air. This is the driest, lowest Td or dewpoint air of the season to date.
Temperatures at 12:30 AM Tuesday were in the mid 30s to low 40s in valleys and the dry air had not yet even come into place ( with strongest advection expected into the predawn-morning hours of Tuesday. This will set the stage for coldest conditions, with rapid temperature drops, Tuesday night into Wednesday morning ).
Strong winds are expected to begin developing at high elevations in the Cumberland Mountains late Wednesday, ahead of the next cold front, with ROARING SW speeds by Wednesday Night into Thursday Morning.
Although orographic forcing will be good, moisture will be limited such that rainfall amounts will likely not be as great as the 0.50″ to 1.00″+ amounts observed with the previous cold front.
The MEAN of the 51-Member European Ensemble group is forecasting a return to anomalous warmth to end October and open up November. However, with significant cold air building at high latitudes over increasing snowpack this new month is not likely to follow the trend of October.
Showers & Possible Thunderstorms Will Increase Into Early Hours Of Friday. Much Colder Air, With Falling Temperatures Are Expected Friday Into Saturday AM.
*The first snowflakes of the season could fall at highest elevations by Friday Night into Saturday Morning ( with light riming on peaks in freezing fog by Saturday AM ).
Below freezing temperatures are expected at highest elevations by Saturday morning, with a heavy frost-freeze developing in many mountain valleys by Sunday morning ( below freezing temps ).
Middle elevation mountain ridges and exposed portions of plateaus will have limited frost with mixing and generally above freezing temperatures. Locally dense fog will be possible along major lakes and rivers-wetlands.
Overnight Into Wednesday Morning
Partly cloudy. Breezy-gusty along ridges. Local areas of valley fog. Winds SSW-SW 5-15 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet. SW to WSW winds 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures varying from 40s to lower 50s in cooler mountain valleys to upper 50s to lower 60s along exposed ridges-plateaus.
Partly cloudy. Unseasonably warm. Winds SSW-SW 5-10 mph, with some higher gusts. Temperatures varying from upper 60s to lower 70s in upper elevations to the upper 70s to lower 80s ( warmer south into the Great Valley ).
Wednesday Night Into Thursday Morning
Partly to mostly clear. Winds SSE-SSW 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges. Temps varying from 40s to lower 50s in cooler mountain valleys to the lower-middle 60s ( warmest along exposed ridges and plateaus ).
Partly-mostly cloudy. Unseasonably warm. Chance of a shower. Winds SW 5 to 10 mph with some higher gusts. Temps varying from mid-upper 60s in the upper elevations to mid 70s to around 80 degrees ( warmer south into river valleys of the Clinch & Holston ).
Thursday Night Into Friday Morning
Showers & thunderstorms becoming likely. Locally heavy rain. Gusty SW winds shifting to NW by morning at 10-20 mph, with higher gusts. Temperatures dropping into the mid 40s to middle 50s by morning ( coldest in the upper elevations ). Wind chills dropping into 30s & 40s on mid-upper elevation mountain ridges by morning.
Mid-Morning Friday Through The Afternoon
Nasty & colder. Showers & drizzle. Low clouds with dense fog across the upper elevations. NW winds 10-25 mph, with higher gusts. Temperatures falling into the mid-upper 30s at upper elevations and into the 40s to around 50 degrees at lower-middle elevations ( along and north-northwest of the High Knob Massif-Tennessee Valley Divide / milder lee of mountains ). Wind chills dropping into the 20s to lower 30s at highest elevations, with middle 30s to lower 40s below 3000 feet in elevation.
Friday Night Into Saturday Morning
Gusty & cold. Showers & drizzle at lower-middle elevations, with a mix or snow showers at highest elevations. Dense fog above 2700-3000 ft. NW winds 10-20 mph, with higher gusts. Temperatures varying from around 30 degrees at the summit level of the High Knob Massif to middle 30s to lower 40s. Wind chills varying from 10s to lower 20s across upper elevation mountain ridges to the upper 20s & 30s at lower-middle elevations ( below 3000 feet ).
*Skies Friday Night may develop breaks lee of the mountains into the Great Valley, with gusty conditions, and little to no precip on downsloping NW winds.
Weather Discussion ( Strong Front )
A large vertical temperature spread is being observed between exposed ridges-plateaus and colder valleys in early hours of the overnight on this Thursday.
As I expected, a strong inversion has formed with deep, sheltered valleys in low-mid 50s at Midnight versus readings still in mid 60s to around 70 degrees along exposed mid-upper elevation ridges.
This update mainly addresses the push of cold air expected to hit Friday into this weekend, with little to no changes in my previous forecast through Thursday.
Strong height falls continue to suggest that a nice band of showers and thunderstorms will form along-ahead of the cold front later Thursday into early hours of Friday.
NOTE this will tend to bring down many leaves into Friday, so be cautious of slick places on roadways that may be leaf covered.
High-resolution short-range models continue to be in good agreement with the European Group in forecasting showers and downpours, with embedded thunderstorms, to arrive by late Thursday into early hours of Friday.
A sharp temperature drop follows with reading sliding into the 40s in Norton-Wise during the day Friday, with 30s at highest elevations atop the High Knob Massif. Gusty NW winds will make it feel even colder. A WINTER COAT will feel good Friday, especially by later in the day.
While the first snowflakes continue to look likely in places along the high Appalachians, the big story for most will be this nasty temperature plunge Friday into Saturday that will make conditions ( in wake of unseasonable warmth ) feel like a summer jump into winter. Get ready!
The sun is about to set upon this stretch of unseasonably warm October conditions.
A strong autumn cold front will be the main weather maker by late Thursday into Friday, with showers & thunderstorms expected along-ahead of the boundary.
A blast of chill will follow the frontal passage to make the day-light hours of Friday raw & NASTY with cold conditions ( especially in upslope locales along and north to northwest of the High Knob Massif & Tennessee Valley Divide ).
The forecast map by later Friday looks like one straight out of the winter season, as low pressure intensifies over the NE USA. This will increase the pressure gradient along the Appalachians with a notable NW flow from the Great Lakes and cold air transport!
Temperatures will be dropping into the 40s in Norton-Wise during Friday afternoon, with 30s at highest elevations in the High Knob Massif. Chill factors on gusty NW winds will make conditions feel even colder. Get prepared now!
Rainfall totals are likely to be heaviest along and west of the Appalachians into early Friday, with more showers and drizzle likely into Friday afternoon & night ( even the first flakes of snow could fall at highest elevations Friday night into early Saturday before conditions begin to improve ).
Mostly cloudy. Low cloud bases across high terrain with dense fog. Light & variable winds. Temperatures varying from the 40s to lower 50s.
Partly-mostly cloudy. Small chance of showers-sprinkles. Light SSE-SSW winds. Temperatures varying from upper 50s to lower 60s in upper elevations to the upper 60s to lower 70s.
Friday Night Into Saturday Morning
Mostly cloudy. Small chance of a shower-sprinkle. Winds SSE-SW at 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges-plateaus. Temperatures from the 40s in coolest valleys to the lower-middle 50s.
Becoming partly cloudy. Light SSE-S winds, except 5-10 mph with some higher gusts at highest elevations. Temps varying from low-mid 60s in upper elevations to the lower to middle 70s.
Saturday Night Into Sunday Morning
Partly-mostly clear. Areas of valley fog. Winds S to SW at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges. Temperatures varying from 40s in cooler mountain valleys to the lower-middle 50s.
Partly cloudy. Light SSW-SW winds generally less than 10 mph. Mild. Temperatures varying from 60s in the upper elevations to the lower-middle 70s.
Weather Discussion ( Mild Pattern )
Some spectacular autumn color has developed in mid-upper elevations of the High Knob Massif, with this weekend thru next week currently expected to offer some of the best color as the peak approaches.
A major reason color is so dependably spectacular in the massif year after year is due to a combination of factors. Endemic, rich northern hardwoods within a mixed-mesophytic forest growing atop both calcareous and clastic stratas amid the wettest area in Virginia ( on average over the long-term ) are driving forces that are superimposed upon a sprawling mass of elevated terrain full of high basins ( wetland valleys, lakes, coves ) & complex terrain.
Although behind schedule, in general, a significant advance in color changes have been observed during the past week amid seasonally cool conditions and abundant sunshine.
The MEAN temperature observed during October 1-12 within high valleys of Big Cherry Lake basin was 52.1 degrees ( the average of sensor locations ), varying from the lower 60s by day to lower 40s at night ( 30s being observed during October 9-12 ).
It is easier to understand the observed differences in color changes when one compares this to the Tri-Cities, amid the Great Valley, where the October 1-12 mean was 61.7 degrees or approximately 10 degrees warmer than local high basins.
The coldest October on record in the Tri-Cities had a MEAN temp of 50.1 degrees in 1988 ( the average is 56.3 degrees ). So conditions recorded in high valleys of Big Cherry Lake during October 1-12 this year would be considered MUCH below average for the TRI.
Although decreases in sunlight along with cooler conditions trigger autumn colorations, it is important to note that its not only the colder nights but also the much cooler days.
The highest temperature observed during the October 1-12 period at the MesoNET site atop Black Mountain ( 4031 feet ) has been 69 degrees, the same as recorded in high valleys of Big Cherry Lake basin ( one sensor location there reaching just 68 degrees ).
High valleys, which are plentiful in the High Knob Massif, tend to have lower MEAN temperatures than might be expected due not only to much colder nights ( than are observed along high ridges when radiation rules over advection ) but also to these cooler daytime temps.
So the best, brightest and most advanced color typically begins developing first along the high basins where cold air drainage occurs at night and days are relatively cool due to elevation in combination with exposure. In most autumns color begins to develop in mid-September, with significant colorations often observed by late September-early October.
Autumn 2016, by contrast, did not see significant color changes begin until early-mid October ( 1-2 weeks later than typical ).
Looking ahead, a mostly dry and mild pattern rules into next week when there is increasing evidence that a large storm system ( of some form ) will develop across the eastern USA.
The MEAN of the 51-Member European Ensembles have in recent days been showing a potential phasing event between a tropical cyclone and a mid-latitude upper air trough which would lead to an orographic forcing episode along the Appalachians.
Needlessly to say, IF that occurred it would be a major precipitation maker for the Mountain Empire. However, it remains too far out in time to know exactly what will occur.
The latest 00z run of the operational European Model coming out as I write now continues to also show such an event. Every run that continues to replicate this will increase the odds of a major event that could again be a headline making storm system. It should be stressed again, of course, that its too early to be sure.
Due to changes at high latitudes, with building heights near Greenland and in the Gulf of Alaska next week, it does appear likely that much cooler ( colder ) air will arrive in 7-10 days. Certainly that increases the odds that there could indeed be cyclogenesis…BUT will that occur in such a position as to give much needed rainfall to those places that need it along the mountains while sparing flood ravaged locations to the east?
Rain showers & rain developing. Winds shifting NE-N and increasing to 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges and plateaus by morning. Cloud bases dropping with dense fog formation on higher ridges. Temps dropping into the 50s to around 60 degrees by morning ( 40s wind chills at highest elevations ).
A chance of rain showers-drizzle. Windy & chilly. Low cloud bases with dense fog above 2500-3000 feet along and north of the High Knob Massif & Tennessee Valley Divide. Becoming partly cloudy late. Winds N to NE at 10-20 mph, with higher gusts. Temps steady or falling into 50s lower-middle elevations and dropping to the 40s-low 50s in upper elevations. Wind chills in upper 30s to lower 40s at highest elevations. Milder conditions lee of the High Knob Massif into river valleys of the Clinch, Powell & Holston drainages.
Saturday Night Into Sunday Morning
Becoming clear. Chilly. Windy across mid-upper elevation mountain ridges. Winds N-NE 5-15 mph, with higher gusts, along middle elevation ridges-plateaus below 2700 feet. N-NE winds 10-20 mph, with higher gusts, on upper elevation mountain ridges. Temperatures dropping into the 30s to lower 40s ( frost and/or fog could occur in any valleys that might be able to decouple, with light-calm winds ). Wind chills in 30s and 40s along ridges-plateaus, except locally into the 20s to lower 30s during gusts on high peaks.
Sunny. Seasonably cool. N winds 5-15 mph, with higher gusts. Temperatures varying from mid-upper 40s in the upper elevations to the mid 50s to around 60 degrees ( wind chills continuing to be a factor at highest elevations ).
Sunday Night Into Monday Morning
Clear. Frost possible in colder valleys. Winds NNW-NNE at 5 to 15 mph, with some higher gusts, along the mid to upper elevation mountain ridges. Temperatures varying from the upper 20s to lower 30s in colder valleys to the upper 30s to lower 40s ( fog possible along main streams-lakes ).
*Multiple nights with the potential of frost formation in mountain valleys is being watched for into the new work week.
Weather Discussion ( Big Changes )
Saturday Night Update
My update Saturday Night is to decrease sustained wind speeds a little into Sunday AM, following a very windy Saturday afternoon in mid-upper elevations.
Orographic forcing aided rainfall amounts as the pressure gradient increased Saturday across the High Knob Massif area, with 1.00″ to 1.50″ rain amounts being common.
This included the water plant at Appalachia Lake where Mark Quillin reported 1.38″ of rainfall. This was in contrast to only 0.31″ of rain measured in Clintwood and just 0.25″ measured lee of the mountains in the Tri-Cities.
An average MIN of 42.1 degrees was observed in the wetland valley during the past 10 days ( i.e., September 28-October 7 period ).
Most of the massif area was engulfed in clouds, with high valleys holding steady near 60 degrees until early Saturday afternoon when a temperature drop started ( temps were several degrees cooler atop adjacent ridges all day ).
By late Saturday afternoon wind chills were notable along the high ridges, as my Field Studies In Microclimatology Class can testify too ( despite layered clothing it felt cold as strong winds swirled fog & occasional rain showers across the high country ).
Many leaves came down, and partially covered roads in the massif, as color is really increasing from Wise on upward in elevation. Hopefully, below the highest ridges, this leaf fall will not be detrimental to the upcoming peak.
ALERT For Dense Fog Developing Into Saturday Morning At Middle-Upper Elevations Along And North Of The High Knob Massif & Tennessee Valley Divide
Orographic pilatus clouds capping the High Knob Massif late Friday was a signal of big weather changes into this weekend, as the pressure gradient around Matthew cranks up orographics behind a passing cold front pushing across the Appalachians. This means a CHILLY weekend ahead!
As Hurricane Matthew crawls along the South Carolina coast an increasing northerly flow will develop across the Appalachians, increasing upslope into the High Knob Massif and Tennessee Valley Divide during the predawn-morning hours of Saturday. This will cause a drop in cloud bases, with dense fog formation engulfing higher terrain locales above the 2500-3000 foot level ( e.g., amid, or just above, the Town of Wise & Sandy Ridge on upward in elevation ).
Drier air will eventually get pulled into the circulation, but low clouds ( and dense fog at higher elevations ) could last for much of the day Saturday before dissipating ( with a rise in cloud bases likely before a complete clearing by Saturday Night into Sunday morning when some valleys could then develop fog as others develop frost IF vertical mixing can locally relax enough to allow a run at dewpoints, which remains to be seen as Matthew churns ).
Most all of this weekend will be dominated by gusty winds across higher elevations, especially mountain ridges, where frost will not be able to form but true wind chills will be felt for the first time ( for a prolonged period ) this autumn.
As the pressure gradient begins to relax, Sunday Night into Monday AM will offer a much better chance for formation of frost in colder mountain valleys. Stay tuned.
*An ALERT For Dense Fog Formation May Be Needed For Middle-Upper Elevations Along & North Of The High Knob Massif-Tennessee Valley Divide Friday Night Into Saturday
*One or more nights with potential of frost formation is being watched for mid-upper elevation mountain valleys next week.
Overnight Into Thursday Morning
Mostly clear. Chilly. Areas of valley fog. SSE winds 5 to 10 mph, with some higher gusts, along middle-upper elevation mountain ridges. Temperatures varying from upper 30s to lower 40s in colder mountain valleys to upper 40s-low 50s.
Mostly sunny. Pleasant. Winds E-SE at 5-10 mph. Temperatures varying from low-mid 60s in upper elevations to the lower-middle 70s.
Thursday Night Into Friday Morning
Becoming partly-mostly cloudy. Winds ESE-SE at 5-20 mph, with higher gusts, on middle to upper elevation mountain ridges. Temperatures varying from the mid-upper 40s to the upper 50s ( warmest on exposed mid elevation ridges ).
Mostly cloudy. ESE-ENE winds mostly less than 10 mph. Small chance of a shower or sprinkle. Temps varying from upper 50s to lower 60s in upper elevations to the upper 60s to lower 70s ( warmer in the Great Valley all these days ).
Friday Night Into Saturday Morning
Rain showers & rain developing. Winds shifting NE-N and increasing to 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges-plateaus. Cloud bases dropping with dense fog on higher ridges ( possibly down to the level of Wise ). Temps dropping into the 50s to around 60 degrees by morning ( 40s wind chills at highest elevations ).
A chance of rain showers-drizzle. Windy & chilly. Low cloud bases with dense fog above 2500-3000 feet along and north of the High Knob Massif & Tennessee Valley Divide. Becoming partly cloudy late. Winds N to NE at 15-25 mph, with higher gusts. Temps steady or falling in the 50s lower-middle elevations and dropping to the 40s-low 50s in upper elevations. Wind chills in upper 30s to lower 40s at highest elevations. Milder conditions lee of the High Knob Massif into river valleys of the Clinch, Powell & Holston drainages.
Weather Discussion ( Chilly Weekend )
Thursday Evening Update
As CAT 4 Matthew gets closer to the Florida coast I have updated to define conditions here through Saturday PM.
Some significant rain will rotate west-northwest into the Appalachians Friday Night-Saturday, with a sharp cut-off likely near or just southwest of the High Knob Massif and Tennessee Valley Divide. The heaviest rains are expected generally along and east-southeast of the Blue Ridge, with at least the chance for some heavier amounts in favored orographic locations with increasing upslope along the western side of the mountain chain.
The timing between arrival of a cold front, from the west, and moisture wrapping around the broad circulation of Matthew will help to dictate where the heavier downpours develop.
The NAM Model group is wanting to develop rain along the Appalachians as moisture interacts with a cold front from the west, with a sharp cut-off producing little to no rainfall in foothills of Kentucky westward of the mountains. This will bear watching given the increasing upslope along the western side of the mountain chain from enhanced flow around Matthew ( i.e., an increasing pressure gradient ).
Regardless of local rain amounts, cloud bases will be dropping on increasingly gusty NE-N winds into Saturday with upsloping and chilly conditions expected ( especially for locations along and NE-NW of the High Knob Massif and Tennessee Valley Divide ). Skies will become partly cloudy, then clear, as drier air invades later Saturday into Sunday ( with windy conditions continuing ).
The Bottom Line…A very chilly weekend is ahead for the mountains with the first true wind chill factors of the autumn season expected across higher elevations as a cold frontal passage combines with an increasing pressure gradient around Matthew. Rain & low clouds ( dense fog at higher elevations ) into Saturday giving way to clearing, gusty conditions later Saturday or Saturday Night-Sunday before conditions calm.
Temperatures are chilly in mountain valleys tonight, with 40s to lower 50s at Midnight Thursday, as sinking air north of Hurricane Matthew is drying the vertical column.
The effect being further enhanced with SE-SSE downsloping along the western side of the Appalachians at low-levels.
Hurricane Matthew is looking better organized on IR imagery in recent hours, after passing Cuba & Haiti, and continues wobbling toward the northwest ( the wobble due to fluxes in convection ).
The current National Hurricane Center track forecast is closely following the 51-member European Ensemble MEAN.
Meanwhile, back here in the Appalachians the current indirect influences from Matthew will become a little more notable into Friday Night-Saturday as the pressure gradient increases. Windy conditions and dropping cloud bases will develop along the mountains on upsloping northerly flow to generate chilly temperatures and some showers-drizzle ( the greatest coverage of showers-rain is expected along and well east of the Blue Ridge ).
Saturday could be a very chilly day along and north-northwest of the High Knob Massif and Tennessee Valley Divide, with temps in the 50s dropping into the 40s at upper elevations ( temps falling into the 50s at lower-middle elevations ). Windy conditions will make it feel colder, especially along mountain ridges-plateaus. Stay tuned for updates.
Partly to mostly clear. Areas of dense fog. Light N to NE winds mostly less than 10 mph on mid-upper elevation mountain ridges. Temperatures varying from the low-mid 40s in upper elevation valleys to the low 50s.
Partly cloudy. Light NE-ENE winds. Temperatures varying from upper 50s to lower 60s in upper elevations to the low to mid 70s.
Monday Night Into Tuesday Morning
Partly-mostly cloudy. Areas of dense valley fog. Winds becoming ESE-SSE at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges. Temperatures varying from the 40s in cooler mountain valleys to mid-upper 50s.
Partly-mostly cloudy. Small chance of a rain shower. Winds SE to SSE at 5-10 mph, with higher gusts. Temps varying from low-mid 60s in upper elevations to the mid 70s ( warmer, every day, as usual into the Great Valley ).
Tuesday Night Into Wednesday Morning
Partly-mostly clear. Areas of valley fog. Winds SE-SSE 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures varying from 40-45 degrees in colder mountain valleys to the low-middle 50s.
Mostly sunny. Winds E to NE at 5-10 mph. Temperatures varying from low-mid 60s in upper elevations to the mid-upper 70s.
Chilly temperatures are expected into Thursday AM with low dewpoint air developing beneath subsidence and drying north of Hurricane Matthew. MINS are forecast to vary from the 30s to lower 40s in colder mountain valleys to the mid-upper 40s.
Weather Discussion ( Mostly Dry )
Some light showers and sprinkles fell upon the high country of the High Knob Massif during Sunday PM, of October 2, as MAX temperatures climbed to around 60 degrees ( from AM MINS in the mid 40s ).
Sections of upper slopes are developing significant color changes while lower slopes, below 2700-3000 feet, remain mostly green.
October 2016 opened foggy and chilly in high valleys, with low temperatures dipping to around 40 degrees in the basin of Big Cherry Lake ( the lowest temps reported in Virginia ).
Following mid 50s to lower 60s during the afternoon of October 1, in wake of the High Knob Hellbender 10K Race, skies became mostly cloudy into Sunday and eventually produced ( as noted above ) some sprinkles-light showers.
While a few rain showers can not be ruled out, especially into Tuesday ( October 4 ), most of the week will again be devoid of any significant rainfall. In fact, the most recent run of the European Model says most of the next 10 days will remain generally dry ( save for a few showers ).
I measured a total of 0.68″ at Big Cherry Dam for the past week, which brought the September 2016 total to 3.40″ ( well below the average ) and the yearly tally to 51.48″ ( with missing moisture in evaporation between hand-measurements not being included ).
The main weather focus in the eastern USA this week will be on powerful Hurricane Matthew. While the mean of all tracks remain off the Atlantic Coast, the exact track is far from set and all interests along the coast will have to keep watching this cyclone very closely.
While no direct impacts are expected locally, indirect effects will, as I so often teach, be observed in the form of sinking air that acts to rebuild and reinforce the upper ridging over the region to allow days to warm as the storm approaches ( this could allow nights to trend cooler in mountain valleys if drying around and below 850 MB occurs due to the general subsidence regime – especially along the western Appalachians ).
A distinct and important westward trend in the composite of model forecast tracks for Hurricane Matthew has been observed during the past 18-hours ( compared the above graphic to the one issued at 2:00 AM or 06z on October 3 ).
Low clouds. Dense fog widespread at upper elevations into the overnight hours, then lifting bases possible by morning. Locally dense fog at middle to lower elevations. Scattered showers with local thunder & small hail possible ( drier to the west & southwest of Pennington Gap ). Light & variable winds. Temperatures dropping into the 40s to lower 50s.
Cloud bases lifting. Becoming mostly to partly cloudy. Seasonally cool. W-SW winds 5-10 mph, with higher gusts, especially on mid-upper elevation ridges-plateaus. Temps varying from the mid-upper 50s in the upper elevations to the mid-upper 60s.
Friday Night Into Saturday Morning
Partly-mostly clear. Chilly. SSW-SW winds 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from the upper 30s to lower 40s in colder valleys of the upper elevations to the mid 40s to around 50 degrees ( milder ridges ). Areas of valley fog.
High Knob Hellbender 10K Race Forecast
A seasonally cool but dry race is forecast this year, with some low clouds and fog possible in a layer that could stream along the base-lower portions of the massif from Powell Valley during the morning, on light SW flow, prior to dissipating into partly cloudy skies as temps warm.
Some variations in temperature along the race course this year will include a start in the 50s ( following early AM lows in the 40s ) within downtown Norton, a rise to around 60 degrees above Legion Park and below the Flag Rock Recreation Area junction with State Route 619, then a fall back into the 50s with increasing elevation above Flag Rock ( these temps for the 10:00 AM to Noon period ).
Please note that breezy SSW-SW winds at upper elevations will make conditions feel more like the upper 40s to lower 50s.
10:00 AM Start In Downtown Norton
55 degrees – A Layer of fog and clouds will be possible just above downtown, along lower slopes of the massif, otherwise partly cloudy conditions are expected.
12:00 Noon At Summit of High Knob
54 degrees ( a crisp feels-like temperature of 48-52 degrees ) beneath partly cloudy skies. SSW to SW winds of 5-10 mph, with some higher gusts.
*This forecast is a go. Good Luck to all runners & walkers!
Partly-mostly sunny. Winds S-SW 5-10 mph, with some higher gusts ( especially on mid-upper elevation ridges ). Temperatures varying from upper 50s to lower 60s in the upper elevations to the upper 60s to lower 70s ( warmer southward into the Great Valley ).
Saturday Night Into Sunday Morning
Partly to mostly clear. Winds SSW-WSW winds 5-15 mph, with higher gusts, on middle to upper elevation mountain ridges. Temperatures varying from 40-45 degrees in cooler mountain valleys to the lower-middle 50s.
Weather Discussion ( Autumn Changes )
A significant weather change in conditions was observed during the Tuesday PM to Thursday PM period, as noted by these dramatically contrasting views from the High Knob Massif Webcam at UVA-Wise.
From pristine autumn skies to a complete obscuring of upper elevations within low clouds and dense fog ( below ).
Conditions in upper elevations of the High Knob Massif were chilly prior to this radical conditions change on September 29, as noted by these readings recorded on the High Knob Massif MesoNET.
Although green still dominates the forest, and autumn color is running well behind its typical schedule in upper elevations of the High Knob Massif, some changes are occurring and many trees are now on the brink of changing-brightening with colorations.
Note along the crest of this high ridge that some trees are flagged, a rather atypical observation for deciduous northern hardwoods versus spruce-fir crestlines ( where coniferous growth is more conducive to flagging of limbs at high elevations ).
AM MINS dipped into the upper 30s to lower 40s within colder mountain valleys during September 28 ( 42 degrees in Clintwood ). Coldest conditions occurring in places not impacted by dense fog. Wetland valleys upstream of Big Cherry Lake having dense fog on every night so far during September in places near Beaver dams.
Note wind chills into the lower 40s have been recorded at 4031 feet elevation by the Black Mountain MesoNET, with likely somewhat lower chills at places like High Knob Meadow ( Lookout ).
Conditions in upper elevations during September 29 were simply nasty, with dense fog all day across the High Knob Massif where numerous showers ( some with thunder-hail ) held temperatures in the 40s to lower 50s during the PM.
A upper-level low has cut itself off from the main jet stream flow across North America. It will be key to conditions that are observed on Saturday for the High Knob Hellbender.
Looking ahead, my forecast for this year’s grueling climb from downtown Norton to the summit level of High Knob, the infamous High Knob Hellbender 10K Race, is dependent upon the current upper-level low moving enough to allow for drier air to stream into the area.
Should this low be slower to move than models currently indicate, which is always possible with upper-lows, then a more cloudy race could result.