ALERT For Ice Storm Conditions At Upper Elevations In The High Knob Massif Through Thursday Morning
Caution is advised for those living and traveling across the High Knob Massif, especially at upper elevations above 3000 feet on State Route 619, 706, Routes 237, 238, 704 & others in the high country. Breaking tree limbs and locally downed trees will be a threat.
Major Ice Storm on Eagle Knob – Cody Blankenbecler Image At 10:50 AM
Major ice storm conditions are revealed in wake of overnight freezing rain, with a mid-morning change to snow on the 4196 foot summit of Eagle Knob of the High Knob Massif. Note bent and drooping trees.
ALERT For Strong Rises On Streams Into Thursday PM
While freezing rain and icing is holding back some water, a strong rise is expected on creeks draining the border area of Wise-Scott-Lee counties and adjacent counties along the Cumberland Mountains. Caution is advised.
*A pocket of cold air aloft will move across the mountains late Thursday into Friday morning to change all lingering precipitation into snow and slowing down run-off.
Expect light accumulations of snow, with a dusting up to 2″ by Friday morning (generally heaviest at upper elevations).
Former Alerts
ALERT For DENSE Fog Formation With Dropping Cloud Bases Tuesday Into Tuesday Night For Locations Along And North Of The High Knob Massif-Tennessee Valley Divide On Northerly Upslope Flow. Caution is advised.
Cloud bases will likely drop as low as the Town of Wise, on northerly upslope flow, with levels as low as 2000 to 2500 feet being possible. As typical, temperatures will remain milder well below cloud bases in downslope locations of the Clinch, Powell & Holston valleys southeast into the TRI area ( Great Valley and Tri-Cities ).
ALERT For Freezing Fog Beginning At Elevations Above 3500 Feet By 10 AM Tuesday — With Dropping Freezing Levels To 2500 Feet By 7-10 PM Tuesday
Dropping temperatures Tuesday will allow the freezing level to slowly decline from upper into middle elevations during the mid-morning to mid-evening period. Riming is only expected to be significant at upper elevations.
Weather Headlines ( November 11-15 )
*Another significant weather system will begin impacting the mountain area by Monday afternoon into Monday night, with widespread rain.
*Strong rises on creeks draining the High Knob Massif will be possible into Tuesday, where recent rainfall has been significant during November.
*Expect falling temperatures Tuesday as winds shift NW-N with readings dropping into the 20s to lower-middle 30s during mid-late afternoon. Cloud bases will obscure elevations above 2500 to 3000 feet.
*A new upper wave renews rainfall by the overnight-to-predawn hours of Thursday, with significant rain amounts. In addition, icing with freezing rain will also be possible in upslope zones along the High Knob Massif and windward slopes of the Tennessee Valley Divide prior to changing into rain Thursday AM.
Strong rises on streams are expected with saturated conditions already existing, raising the potential of localized flooding. Creeks draining the High Knob Massif are expected to ROAR into the afternoon.
*A pocket of cold air aloft could support a change to snow by later Thursday into Friday morning with the first widespread, light snow accumulations.
Mountain Area Forecast ( Nov 13-15 )
Overnight Into Tuesday Morning
Low clouds, with areas of fog. Rain redeveloping overnight into the morning. Winds becoming WNW-NNW at generally less than 10 mph. Temperatures holding near steady in the 40 to 45 degree range. Wind chills in the 30s to lower 40s.
Mid-Morning Tuesday Through The Afternoon
Turning colder. Lowering cloud bases with dense fog at mid-upper elevations ( generally above 2000-3000 feet ). Freezing fog developing at high elevations, with dropping freezing levels through the afternoon. Nasty and cold with a chance of light showers-drizzle or mixed precipitation. Winds NW-N at 5-15 mph with higher gusts, especially at higher elevations. Air temperatures falling through the 30s ( into 20s at high elevations by mid-late afternoon ) in locations along & north of the High Knob Massif-Tennessee Valley Divide. Wind chills falling into the 20s, with 10s at highest elevations, during mid-late afternoon.
Tuesday Night Into Mid-Morning Wednesday
Low clouds-dense fog and freezing fog. Chance of flurries or drizzle-freezing drizzle. Cloud bases will try to lift and break during the overnight to mid-morning period. Winds NNW-NNE at 5-15 mph. Cold with temperatures varying from upper 10s to upper 20s ( coldest at upper elevations ). Wind chills in the 10s to lower 20s on exposed mountain ridges and plateaus ( single digits possible in gusts on highest peaks ).
Wednesday Afternoon
Partly-mostly cloudy (mid-high clouds). Unseasonably cold. NE-E winds at 5-15 mph, with some higher gusts. Temperatures in the 30s to near 40 degrees. Wind chills in the 20s to lower 30s ( coldest at highest elevations ).
Wednesday Night Into Thursday Morning
Rain developing, with freezing rain possible ( most widespread at upper elevations in the High Knob Massif ). Low cloud bases with dense fog at upper elevations. Winds ESE to SSE at 10-20 mph with higher gusts along mountain ridges. Cold with temps in the 30s, except around freezing in colder locations. The temperature will tend to rise into the overnight to mid-morning in locations receiving an increase in downslope flow on ESE-SSE winds.
Weather Discussion ( NASTY )
A simply nasty weather pattern is gripping the mountain region. Precipitation began in frozen forms, with freezing temps, at highest elevations within the Cumberland Mountains on Monday (*).
*Especially atop the High Knob Massif and on the peak of Black Mountain, with mixed precipitation amid evaporative cooling.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Initial column cooling was supported by evaporation to drop air temperatures to around freezing during the first hour or two of precipitation, with Doppler radar bright banding also indicating this period aloft.
Black Mountain Mesonet – Ending At 1:15 PM on November 12, 2018
Tuesday is going to be an even nastier day in terms of dropping temperatures and a damp, bone-chilling feel to the air. Low-level moisture convergence and a drop in cloud bases along and north of the lifting zone of the High Knob Massif-Tennessee Valley Divide will support the worst, most nasty conditions.
NAM Model 850 MB Temp-Air Flow Forecast At 7 PM Tuesday – November 13, 2018
A rather classic orographic upslope flow-adiabatic cooling setting is being forecast Tuesday on weak cold air advection into slopes facing inflowing air along the Cumberland-Allegheny Front.
A prolonged period of riming will occur at high elevations as air temps drop to freezing by mid-morning Tuesday at elevations above 3500 feet. The freezing level will then decline through the afternoon, eventually dropping to around or below 2500 feet during Tuesday evening.
NAM Model Forecast Sounding At 4 AM Thursday – November 15, 2018
The next main weather problem develops late Wednesday into Thursday morning, with a strong low-level inversion supporting cold air below 5000 feet. With ESE to SSE flow this type of atmospheric sounding often supports icing in upslope locations of the High Knob Massif, and along the eastern slopes of the Blue Ridge.
The remainder of the area will have temperatures at or above freezing, with a rising tendency as winds downslope more strongly into Thursday morning.
The icing threat will then diminish in the High Knob Massif and along the Blue Ridge as Thursday progresses and winds change direction in advance of a strong upper-level wave ( below ).
NAM Model 850 MB Temp-Air Flow Forecast At 7 PM Thursday – November 15, 2018
A pocket of cold air aloft associated with an upper-level low and strong PVA ( positive vorticity advection ) will support the potential of the first widespread snow accumulation during Thursday evening into early Friday.
NAM Model 500 MB Vorticity Forecast At 7 PM Thursday – November 15, 2018
Amounts of 1″ to 3″ will be possible, but stay tuned for later updates on this first widespread sticking of the season.
The coldest temperatures of this young 2018-19 cold weather season were observed into Saturday morning, November 10 at high elevations, and Sunday morning within mountain valleys. Although skies cleared after some flurries and snow showers, conditions continued changing and interacting with complex terrain.
High Knob Massif Webcam – University of Virginia’s College At Wise
MIN temperatures fell into the 10s at high elevations in the High Knob Massif into Saturday morning, with 0 degree or lower wind chills in gusts on highest peaks.
The atmospheric setting began changing late Saturday into Sunday morning, with dry air & warm air advection at high elevations supporting cold air drainage and a temperature plunge into mountain valleys.
Black Mountain Mesonet At 6:55 AM on Sunday – November 11, 2018
Temperatures actually rose Saturday night into Sunday AM at high elevations, with 30 degrees reported by the mesonet site on Black Mountain at 6:55 AM Sunday (above). This was down from 32 degrees just over an hour earlier. MAX temps during Saturday, by contrast, held in the 20s all day at high elevations in the High Knob Massif and Black Mountain.
Norton Elementary School Weatherbug At 6:55 AM on Sunday – November 11, 2018
At the same time, 6:55 AM Sunday, a temperature of 17 degrees was reported by the Weatherbug site at Norton Elementary School; however, it should be noted that the actual air temperature at 5 feet above ground level was in the 14 to 15 degree F range ( the Norton ES sensor is 15-20 feet above ground level next to the school roof and above large asphalt areas instead of natural surfaces ).
Minimum Temperature Reported In Burkes Garden – Sunday – Nov 11, 2018
Minimum temperatures fell into upper single digits to lower 10s in colder mountain valleys from the High Knob Massif to Burkes Garden, at elevations above 2700-3000 feet, with 11 degrees officially in Burkes Garden.
That is the way to nail down a temperature forecast within complex terrain ( a couple days ahead of time )!
The first of two significant blasts of cold air will begin to push into the Appalachians late Friday into Friday night, with rain giving way to a chance of flurries and snow showers ( especially along the upslope side of the mountains on WNW-NW air flow trajectories ).
Unseasonably cold air is expected during Saturday into Sunday morning as skies clear, with deep blue, polar-arctic air as dewpoints tumble.
Single digit to below zero wind chills will develop at highest elevations later Friday night into Saturday morning. Caution is advised for anyone hunting or planning to be outdoors for any length of time.
This sets the stage for near record to record level cold into Sunday morning, especially in mountain valleys, with temperatures in the 10s and 20s ( rising through the 20s to near 30 degrees F at highest elevations to contrast with the potential of single digits in upper elevation mountain valleys ).
*Coldest single digit temperatures will be possible in colder valleys from the High Knob Massif to Burkes Garden within southwestern Virginia. Note these are actual air temps and not wind chills (with cold air drainage and near calm wind).
Another significant weather system is expected next week, with a much better potential for accumulating snow as an even colder blast of air strikes by later Tuesday into Wednesday AM ( November 13-14 ).
A zonal continental flow field is expected to develop, with much milder conditions, later next week into the weekend of November 17-18.
Mountain Area Forecast
Friday Morning Into The Afternoon
Significant rain develops Friday with a temperature fall beginning during mid-late afternoon as winds shift WNW-NW at 10-20 mph.
Friday Night Into Saturday Morning
Sleet, flurries and snow showers develop Friday night into Saturday morning. Accumulations of a dusting up to 1″ will be possible ( especially upper elevations ). Little to nothing along lee side of mountains.
Gusty WNW-NW winds at 10-20 mph, with higher gusts will generate nasty wind chills. Temperatures fall into mid-upper 10s to the mid-upper 20s ( coldest at highest elevations ), with wind chills varying from 10s to lower 20s below 3000 feet to the single digits and 10s at elevations above 3000 feet ( around or below 0 degrees in gusts on highest peaks ).
Rime formation expected at elevations above 3000 to 3300 feet as temperatures fall below freezing amid orographic clouds.
Saturday Morning Through The Afternoon
Saturday morning clouds and any flurries give way to clearing, with deep blue skies. Unseasonably cold for early November with temperatures varying from 20s at upper elevations to the low-mid 30s (20-25 degree max temperatures at highest elevations).
NW-N winds at 5-15 mph will produce wind chills in the 10s & 20s, to near 30 degrees at lower elevations, except 0 to 10 degrees in gusts during the morning at highest elevations. Milder conditions expected into lower elevations of the Clinch, Powell, and Holston valleys on downslope flow.
Saturday Night Into Sunday Morning
Expect mostly clear and unseasonably cold conditions Saturday night into Sunday morning. A large vertical temperature spread is expected to develop between exposed ridges-plateaus and bitter valleys. Min temps will vary from 10s in valleys ( single digits likely in coldest valleys at upper elevations ) to slowly rising readings through the 20s to around 30 degrees at highest elevations by Sunday AM.
Weather Discussion (Early Winter)
Friday Afternoon Update
High Knob Massif Webcam – University Of Virginia’s College At Wise
Low clouds bases, obscuring elevations above 2800 to 3000 feet, marks the beginning of a significant temperature drop through Friday night into Saturday morning.
Although some flurries and snow showers will develop, the main story will be the cold as wind chills fall to dangerous levels for those unprepared for this early blast of winter. This will be especially true for those living and traveling across middle-upper elevations above 2000-3000 feet.
Previous Discussion
A early winter weather pattern will dominate the mountain landscape through coming days, with only a brief break in between these first two blasts of early season polar-arctic air.
Looking SE Across The Crest of the High Knob Massif – November 3, 2018
More and more trees will become bare in coming days, with peaks observed during October 15-25 above 3000 feet and during October 25-November 5 at elevations below 3000-3200 feet ( unusually late ).
Lower North Slopes of High Knob Massif on November 3, 2018
The first accumulating snow and rime was featured into early hours of November 3.
Rime Coated Cow Parsnip At Upper Elevations – High Knob – November 3
*Frosty cold conditions are expected, especially in mountain valleys, on Wednesday-Thursday mornings in advance of the first of two important weather systems.
*Winds become gusty Thursday night with rain developing into Friday morning. Low clouds, wet, chilly conditions are expected Friday at high elevations and across the area for much of this weekend into Monday.
*Unseasonably cold conditions with slowly dropping temps Saturday will mark the start of a period with much below average conditions which extends into early Tuesday. The days of October 27 and October 29 are looking coolest in the short-term, with October 29 expected to modify more by late in the day than previous model runs indicated.
*A warmer break is expected for Halloween ahead of huge, cold upper-air trough development over North America as Hurricane Yutu recurves and becomes absorbed into the Polar Jet Stream at higher latitudes. Stay tuned for later details on how this will impact local conditions.
Overnight Into Wednesday Morning
Clear & cold. Winds NNW-NNE at 5-10 mph, with some higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from lower-middle 20s to the low-mid 30s ( coldest in upper elevation valleys ). Wind chill factors in the 20s & 30s ( coldest highest ridges ).
Wednesday Afternoon
Mostly sunny ( few high clouds possible ). Blue skies. Seasonally chilly. Light N to NE winds generally less than 10 mph. Temperatures varying from the low-mid 40s to the lower-middle 50s ( coolest at upper elevations ).
Wednesday Night Into Thursday Morning
Mostly clear, then increasing high clouds into morning. Large vertical temperature difference developing between colder mountain valleys & milder ridges-exposed plateaus. Light winds. Temperatures varying from the lower 20s to the lower-mid 40s on exposed ridges-plateaus ( 10s possible locally within high valleys from the High Knob Massif to Burkes Garden ).
Thursday Afternoon
Increasing and thickening high to mid-level clouds. Chilly. Generally light winds. Temperatures in the 40s to lower-mid 50s, coolest in upper elevations.
Thursday Night Into Friday Morning
Increasing & lower clouds with rain developing overnight into morning. Becoming gusty. Winds SE-SSE at 5-15 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. Winds SE-S at 10-20 mph, with higher gusts, mountain ridges above 2700 feet. Chilly with temperatures dropping into the upper 30s to middle 40s ( coolest high elevations ). Low clouds with dense fog at upper elevations. Wind chills in the 20s & 30s on mid-upper elevation ridges.
Friday Morning Through The Afternoon
Morning rain, tapering to showers or drizzle into the afternoon. Low clouds and areas of fog. Winds SE to S at 10-20 mph, with higher gusts in mountain wave zones of Powell Valley and the Clinch River Valley. Winds SSE-S at 20-30 mph, with higher gusts above 2700 feet (winds may gust over 40 mph at high elevations & in breaking waves ). Temperatures varying from low-mid 40s to low-mid 50s (coolest at upper elevations). Wind chills in the 20s & 30s at high elevations.
Circulation around the first Nor’easter of the season will be driving a W-NW upslope flow Saturday into Sunday morning across the mountains. Most places will see rain showers-drizzle, but some snow will be mixing in at high elevations. A small accumulation will be restricted to highest peaks, with riming also possible amid clouds.
Saturday Morning Through The Afternoon
Periods of showers & drizzle. Low clouds and dense fog at upper elevations. Showers may mix with or change to snow highest elevations. Winds W-NW at 10-20 mph with higher gusts on mid-upper elevation ridges. Temperatures steady to slowly falling through the 40s at low-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide and through the 30s at upper elevations. Wind chills in the 30s and 20s on higher mountain ridges.
Saturday Night Into Sunday Morning
Periods of showers & drizzle. Snow showers-flurries at highest elevations. Low clouds with dense fog at upper elevations. Winds W-NW at 5-15 mph with higher gusts on middle-upper elevation ridges. Temperatures varying from lower 30s to lower 40s ( around 30 degrees highest peaks ). Wind chills in the 30s & 20s, except 10s in gusts on peaks above 3600 feet.
Weather Discussion ( Winter Pattern )
Although autumn color is peaking ( nearing or past ) at upper elevations in the High Knob Massif, a pattern more like winter will be developing in coming days.
Autumn Color On Northern Slopes of High Knob Massif
Conditions deteriorate into Friday as remnants of former Hurricane Willa get absorbed into the upper-level flow and a new low pressure lifts northeast out of the Gulf of Mexico.
Sunset From The High Knob Massif – October 18, 2018
Although the track of this Gulf low will be right for snow, temperatures will remain a little too warm; although, the conditions will be simply nasty and unseasonably chilly.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 3-7
A deep, winter-like upper-level trough digs into the region in wake of this first nasty system, with really cold air, more showers and a chance for some snow ( especially at higher elevations ) as temperatures go sub-freezing.
*The first snowflakes of this 2018-19 cold season fell at the summit level of the High Knob Massif during early hours of October 21. The first riming also briefly developed. Wind gusts to around 50 mph blasted the high summits prior to arrival of the coldest air into predawn hours of Sunday.
European Model 850 MB Temperature Anomalies Forecast: Days 4-8
The European Model is forecasting mean temperatures to hover around freezing during the final days of October at the summit level of High Knob, which translates to some unseasonably cold conditions at middle-lower elevations.
Frost will become widespread across the area by overnight into Thursday morning.
Due to breezy-gusty northerly winds, sites exposed within middle elevations will have less frost than more sheltered locations (temperatures at high elevations will still reach freezing even with wind). Fog will be likely along major river valleys and lakes.
*ALERT For Freeze Within Mountain Valleys – Coldest Temperatures Expected During Thursday Night Into Friday Morning
Frost will be patchy to widespread in mountain valleys and limited to none across exposed mountain ridges as a notable temperature inversion develops. The coldest temperatures of this initial chilly shot will occur in mountain valleys during Thursday night into Friday morning.
Fog will be possible again along major river valleys, with latent heat of condensation offering protection from the colder air expected in valleys with little to no fog.
Colder mountain valleys will have a hard freeze, with the coldest air expected in upper elevation valleys from the High Knob Massif to Burkes Garden due to very low dewpoint air and drainage into high valleys.
*First Widespread Freeze This Weekend
The first true blast of winter-like air will arrive this weekend with falling temperatures Saturday and unseasonably cold air Sunday ( October 21 ).
This blast of air will support the first widespread freeze, with even milder river valleys likely to dip below freezing.
Temperatures are likely to remain below freezing all day Sunday at upper elevations, with temps struggling in the 30s at lower-middle elevations along and north of the High Knob Massif-Tennessee Valley Divide. Potential for the first sticking snow is also being monitored for Sunday Morning, especially at upper elevations. Stay tuned for updates.
Former Alerts
ALERT For Dropping Cloud Bases And Dense Fog On Upsloping Northerly Winds At Mid-Upper Elevations Along & North Of The High Knob Massif-Tennessee Valley Divide For Later Monday Night Into Tuesday
A wind shift behind a cold front will combine with lingering low-level moisture under a developing inversion to develop dense fog at mid-upper elevations along and north of the High Knob Massif-Tennessee Valley Divide later Monday evening into Tuesday. Caution is advised.
Weather Headlines
*Raw, damp & chilly conditions are expected Tuesday in advance of a dewpoint front that will scour out abundant low-level moisture by Wednesday.
*The first widespread frost and freeze of the season is expected to develop Wednesday Night into Thursday Morning, with temperatures dropping into the 20s to around 30 degrees in most locations. Protective fog will be possible along major river valleys-lakes.
Upper air ridging will be building over the western USA as a deep trough develops over the northeastern USA in coming days. Note a split flow pattern. A developing central-Pacific based +ENSO, also known as a Modoki El Nino, will be a significant player in weather conditions expected during Winter 2018-19.
*A below average temperature pattern is generally expected to dominate the remainder of October, with up-down swings during frequent frontal passages.
Monday Night Into Tuesday Morning
Rain showers. Turning cooler with dropping cloud bases and dense fog formation at elevations around and above 2500 feet ( along and north of the High Knob Massif and Tennessee Valley Divide ). Winds shifting NNW to NNE at 5-15 mph with higher gusts. Temperatures dropping into the 40s ( around 40 degrees at high elevations ). Wind chills falling into low 30s to low 40s ( coolest high elevations ).
Tuesday Morning Through The Afternoon
Low clouds & chilly. Chance of rain showers. Light winds becoming SW at 5 to 15 mph, with higher gusts, by late, on middle-upper elevation mountain ridges. Temperatures in the 40s to lower 50s. Wind chills in the 30s higher ridges.
Tuesday Night Into Wednesday Morning
Mostly cloudy (mid-high clouds following dissipation of low clouds). Chance of a shower or sprinkles early. Areas of fog possible in valleys. Winds W-NW at 5-15 mph, with higher gusts. Temperatures in the mid 30s to middle 40s. Wind chills dropping into the lower 30s to around 40 degrees.
Wednesday Afternoon
Mostly sunny, blue skies (some high clouds possible). Crisp and breezy to gusty. WNW to NW winds 10-20 mph with higher gusts ( especially mountain ridges ). Temperatures in the upper 40s to lower 60s, coolest at upper elevations.
Wednesday Night Into Thursday Morning
Clear & cold. Frost and sub-freezing conditions becoming patchy to widespread. Fog possible in major lake and river valleys. Breezy to gusty NNW-NNE winds diminishing to generally less than 10 mph into morning. Temperatures dropping into the mid 20s to the low-mid 30s ( coldest in high mountain valleys and on highest mountain ridges ).
Thursday Afternoon
Sunny. Blue skies. Light & variable winds. Temperatures varying from low-mid 40s to the low-mid 50s ( coolest in upper elevations ).
Thursday Night Into Friday Morning
Mostly clear. Frosty cold valleys. A large vertical temp spread developing between colder valleys and exposed plateaus-ridges. Light SSE-SW winds along mid-upper elevation mountain ridges. Fog along major river valleys.
Temps varying from the 10s to middle 20s in colder valleys to the middle-upper 30s on exposed portions of mountain ridges and plateaus.
A major weather pattern change is occurring just in time for the 2018 Cloudsplitter race, with a radically different air mass expected to be in place over the High Knob Massif versus last weekend.
Model Forecast Sounding At 8:00 AM Saturday – October 13, 2018
Unlike during the Hellbender Race, when even the summit of Mount Whitney would have failed to reach the freezing level, this weekend the freezing level will be low enough to intersect the summit of High Knob, especially on Saturday as the race begins.
High-Resolution Model Time-Height Cross Section During Friday-Saturday ( Oct 12-13)
Dry air will be abundant aloft, but low-level moisture is expected to increase and deepen vertically again in the Friday Night to mid-morning Saturday period as a reinforcing boundary passes and winds shift more strongly to the NW for a period of time.
Although most of this weekend will remain dry with respect to falling precipitation, surface conditions will be wet from recent rain. A chance for some light showers during the predawn to post-sunrise period Saturday and again on Sunday, as warmer air begins to push back over the region, will keep conditions somewhat unsettled and changeable.
*Weather conditions are always changeable with the large variations in elevation and terrain across the High Knob Massif area. These synoptic-scale ( or large-scale ) weather changes will add to this variability through the weekend.
Chilly air and low wind chills, versus recent mild conditions, will be a factor that runners will need to be prepared for, especially along ridges at the upper elevations ( 3000 to 4200 feet levels ).
Forecast Details…Temps in Degrees Fahrenheit
Friday Morning Update
A low cloud deck held through the night with dense fog and low clouds continuing to engulf highest elevations this AM.
High Knob Massif Webcam – University Of Virginia’s College At Wise
It is a wintry morning up top with 34 degrees and wind chills in the 20s, amid dense fog-low clouds. This is what conditions will be like into Saturday morning, only even more nasty for the 8:00 AM start of the Cloudsplitter 100.
Wintry Morning On Eagle Knob of High Knob Massif – Friday ( October 12, 2018 )
By the time first runners reach the summit level conditions could have a chance to improve, but I would not bet on much since I expect cloud bases to be slow to break Saturday.
Friday Night Into Saturday Morning
Becoming cloudy. Chance of rain showers. Flurries or sleet pellets possible at highest elevations. Light rime formation becoming possible on trees and vegetation in high gaps and on the peaks of Eagle Knob, High Knob, and Little Mountain Knob and Camp Rock Knob into Saturday AM.
Winds WNW-NW 5-15 mph, with some higher gusts. Temperatures dropping to around 30 degrees on the highest peaks, with widespread 30s above 3000 feet elevation. Wind chills dropping into the 20s above 3000 feet, with a period featuring upper 10s to lower 20s on highest peaks.
Saturday Morning Through The Afternoon
Low clouds giving way to partly cloudy skies. Chilly. Light northerly winds. Temperatures varying from upper 30s to lower 40s above 3300 feet, with mid-upper 40s to low 50s degrees at lower sections of the race course ( middle 50s at lowest elevations near Hanging Rock Recreation Area and the Devil Fork Loop ).
Saturday Night Into Sunday Morning
Mostly cloudy. Becoming gusty along mountain ridges at middle to upper elevations above 2700 feet. Winds S-SW at 10-20 mph, with higher gusts. Temperatures mainly in the 40s. Wind chills in the 30s to lower 40s. Calmer conditions, with less wind, is expected in hollows and deep gorges.
While the temperature trend will feature near steady to slowly rising readings on exposed mountain ridges, the possibility for temp drops into the 30s, especially during Saturday evening before clouds thicken, will need to be respected within mountain hollows and valleys more sheltered from wind and mixing.
Sunday Morning Through The Afternoon
Mostly cloudy with a chance of rain showers. S-SW winds 5-15 mph, with higher gusts ( especially on mountain ridges ). Temperatures in the 40s at upper elevations, above 3300 feet, with low-mid 50s at lower elevations of the course.
*A chilly air mass will be felt through the next several days, with shocking temperatures ( especially when factoring in wind chills at higher elevations ) in comparison to the mean of recent months.
*Unsettled conditions will occur as the remnants of Michael race away into the Atlantic and a secondary cold front drops into the mountains Friday Night into early Saturday. The first pellets of sleet or flurries & light rime will be possible at highest elevations, with a chance of a few cold rain showers in other locations.
*The first temperatures at freezing will occur at highest elevations, with the first sub-freezing wind chills at upper elevations on both Friday & Saturday mornings. Runners in the Cloudsplitter 100 Race will need to be prepared for these conditions.
*A southerly flow redevelops during the second half of the weekend, with warm air advection and increasing clouds. Wind chills will continue to be a factor in the upper elevations ( especially along high ridges ).
Thursday Night Into Friday Morning
Mostly cloudy. Turning much colder. Low clouds-fog with a chance of drizzle or light riming (highest peaks). NW winds 5-15 mph with some higher gusts. Temperatures dropping into the 30s to lower 40s ( around 30 degrees at on highest peaks ). Wind chills dropping into the 20s and 30s ( coldest at highest elevations ).
Friday Morning Through The Afternoon
Becoming partly to mostly sunny ( blue skies ), then increasing high clouds by late. Light to occasionally breezy W-NW winds. Seasonably chilly with temperatures varying from upper 40s to lower 50s at upper elevations to the mid 50s to lower 60s. Wind chills in the 30s to lower 40s at the highest elevations.
Friday Night Into Saturday Morning
Becoming cloudy. Chance of rain showers. Flurries or sleet pellets possible at highest elevations. Winds WNW-NW 5-15 mph, with some higher gusts. Temperatures dropping into the 30s to lower 40s ( around 30 degrees on highest peaks ). Wind chills dropping into the 20s and 30s, except upper 10s to lower 20s on highest peaks.
Saturday Morning Through The Afternoon
Low clouds giving way to partly cloudy skies. Chilly. Light northerly winds. Temperatures varying from upper 30s to lower 40s at upper elevations to the upper 40s to low 50s.
Saturday Night Into Sunday Morning
Mostly cloudy. Becoming gusty along mountain ridges. Winds SSE to S at 5-15 mph, with some higher gusts, on mountains ridges below 2700 feet. Winds S-SW at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures mainly in the 40s. Wind chills in the 30s to lower 40s ( coldest at upper elevations ).
Be sure to check out What Makes High Knob Special, the latest published series by Wally Smith and Wayne Browning which talks just a little bit about this great mountain mass (scroll down to article links).
Weather Discussion ( Chilly Air )
Friday Morning Update
A low cloud deck held through the night with dense fog and low clouds continuing to engulf highest elevations this AM.
High Knob Massif Webcam – University Of Virginia’s College At Wise
It is a wintry morning up top with 34 degrees and wind chills in the 20s, amid dense fog-low clouds. This is what conditions will be like into Saturday morning, only even more nasty for the 8:00 AM start of the Cloudsplitter 100.
Previous Discussion
Falling temperatures through Thursday afternoon are just the beginning of a chilly period of weather conditions as Autumn 2018 finally decides to arrive.
High Knob Massif Webcam – University Of Virginia’s College At Wise
As of late afternoon Thursday air temperatures had fallen into the 40s, and wind chills into the 30s, at the summit level of High Knob to mark the beginning of a chilly to cold period of conditions amid the high country. A radical change, indeed, for runners taking part in the Cloudsplitter 100 race through this weekend.
Thursday afternoon breaks in the overcast will close back up as northwest flow and cold air advection drop air temps significantly into Friday morning. Clouds bases engulfing the summit of High Knob will lower to cover more of the high country into the upcoming night ( the first light riming may occur toward Friday morning on peaks ).
Clouds will break and Friday skies will feature a classic autumn look, with cumulus hung amid deep, blueness.
Conditions then begin changing Friday night into early Saturday as low-level moisture increases again and cloud bases drop back over the high country. Although most places will have a chance of showers, the first frozen precipitation types will be possible at high elevations during the predawn to post-sunrise period Saturday.
*The first light accumulation, or dusting, of snow will be possible farther northeast in the northern mountains of West Virginia at the highest elevations. A sign of the season upcoming.
Sunshine returns Saturday, eventually, and then more changes occur as moisture begins streaming across the USA from remnants of Sergio ( moving from the eastern Pacific into the southwestern USA ).
The Bottom Line, a much cooler but changeable period of weather is expected through this weekend.
My forecast verified well with respect to temps, wind, and relative humidity levels in the High Knob Massif, with the main problem being related to a rapid break up and dissipation of fog over the Norton Valley.
GOES-16 High Resolution Visible Image At 9:42 AM on October 6, 2018
A solid deck of fog is visible in Powell Valley and along the Clinch River Valley at 9:42 AM, just prior to the beginning of Hellbender 2018, with fog along the Powell River from near Norton through Appalachia.
Fog remained in Powell Valley and the Clinch River Valley at 10:02 AM ( below ), but was dissipating fast outside these locations. I had forecast a fog strip to extend from Powell Valley to just above Norton, along and above the Benges Rock section of the route.
GOES-16 High Resolution Visible Image At 10:02 AM on October 6, 2018
Dry air aloft, which helped high valleys drop well down into the 50s, also aided fog dissipation more quickly over the Norton Valley and a faster rise in temperatures between 8 AM and 10 AM.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Beautiful skies greeted race time in the view looking south from UVA-Wise ( fog in Powell Valley, of course, not being visible from this perspective ).
GOES-16 High Resolution Visible At 3:02 PM on October 6, 2018
The mid-day temperature reached 72 degrees on High Knob, with 70-80% relative humidity, which was also the max for the day as persistent cumulus cloud formation helped hold temperatures down during the afternoon.
Hellbender 10K Race Forecast – 2018
This is a detailed look at the atmosphere during this year’s race, which is highly anomalous for High Knob or any mountain at this latitude in early October.
*Reference my Bottom Line and forecast below to omit this more technical discussion, which some will find interesting for the meteorology-terrain interactions.
The forecast sounding ( below ) at race time Saturday is one featuring a freezing level which is around 14,760 feet above mean sea level or, to put that into better perspective, if the tallest peak in the continental USA ( Mount Whitney ) were standing here the peak would still be just shy of the 0 C or 32 F degree Freezing Level. Simply amazing!
NAM 3 KM Model Forecast Sounding At 10:00 AM Saturday – October 6, 2018
Drier air is forecast to advect over the area aloft, as lower level air remains moist = a good chance for fog formation into Friday night-Saturday morning even though this high resolution NAM 3 KM Model is not forecasting a complete saturation near the surface, one of several adjustments which must be made to such models to more accurately depict weather conditions in the mountains.
Observe that the RH ( relative humidity ) in the 300-850 MB layer is forecast to be in the 35-40% range, over top of air that is 100% saturated near the surface ( in reality, not quite on the model ).
NAM 3 KM Model Forecast Sounding At 11:00 AM Saturday – October 6, 2018
A conditionally unstable atmosphere will be in place, which means it will be stable while unsaturated and unstable if it becomes saturated. The lower right inset shows Theta-E or Equivalent Potential Temperature, which decreases with increasing height to indicate that any layer becoming saturated will develop convective instability.
This is one reason that hit-miss showers and thunderstorms must remain in the forecast; although, with luck any local development will not occur until after the race is completed. The European and other models are forecasting a chance of localized development between 8:00 AM and 2:00 PM.
A low-level boundary layer inversion is expected to form into the overnight-Saturday morning with a combination of radiational cooling and drainage of cooling air downward from higher elevations in the High Knob Massif into the Norton Valley and adjacent Powell Valley.
Warmer air over cooler air is stable in the valley fog layer, but there will be a considerable amount of mixing near the top of this layer. Runners beginning in downtown Norton by 10:00 AM may be just beneath a fog layer, and depending upon how fast it can mix out could be running upward into a corridor of fog before climbing above the fogginess with increasing elevation.
NAM 3 KM Model Forecast Sounding At 12:00 ( NOON ) Saturday – October 6, 2018
Due to vertical mixing, the relative humidity along higher sections of the race course is not expected to drop below 70 or 80%; although, it should feel notably better than near saturated to saturated conditions at lower levels.
A transition from mountain to valley air flow will be aiding this vertical mixing process during the post-sunrise to mid-day period ( centered on mid-morning ).
Bottom Line, Forecast & Race Timeline
High Knob Massif Webcam – University Of Virginia’s College At Wise
The early evening prior to race day ( above ) features a notable layer of haze beneath clear skies ( drier air aloft ) which will be increasing overnight into Saturday morning to help generate formation of fog in valleys. Fog will attempt to grow in depth vertically into the predawn-early morning hours Saturday.
Vertically tall clouds above, and some localized showers, arising from within the moist boundary layer. Such will also be the case during this weekend.
An unseasonably mild and humid atmosphere will be in place for Hellbender 2018, with light winds. This is relative to what is more typical for early October.
There will be humidity changes vertically along the race course, with near saturation to saturation at lower levels versus less humid air with mixing at higher levels of the course ( but still humid for this time of year ).
Cooler air will be featured in the morning near the base with fog, or layers of fog, expected in between downtown Norton and the Flag Rock & Upper Norton Reservoir junctions with State Route 619.
Fog will mix out over time, and although the timing of this is unknown it is expected that air will be humid and close to saturation ( if not saturated ) in lower portions of the race course.
While valleys will be cooler than the summit level in the morning, this will reverse during mid-morning into mid-day Saturday as the low-level inversion mixes out and warms to unseasonable levels.
Higher sections of the race course are expected to feature notably drier air, versus saturation below, and more pleasant conditions into mid-day with temperatures in the 60s to around 70 degrees.
*An overnight update features the addition of possible fog formation at the summit level into morning with 4 AM RH values near 100%. If this occurs and does not mix out then higher sections of the course will have more humid air. Drier air aloft may still be able to keep it mixed out?
Friday Night Into Saturday Morning
Chance of a localized evening shower or thunderstorm, then becoming partly-mostly clear. Dense fog developing during the evening-overnight, especially in mountain valleys such as Powell Valley and the City of Norton ( and Clinch-Powell river valleys ). The fog layer may build vertically to include the Wise Plateau ( a possibility that has to be noted ).
Light S-SW winds, except 5-10 mph with some higher gusts on upper elevation mountain ridges. Temperatures varying from middle 50s to lower-middle 60s ( coolest high valleys ).
Saturday Morning Into The Afternoon
Partly to mostly cloudy with a chance of hit-miss showers and thunderstorms, especially during the afternoon. Winds S-SW at generally less than 10 mph. Temperatures varying from the upper 60s to the low-mid 70s ( coolest at highest elevations ) in the High Knob Massif, with upper 70s to lower 80s in surrounding lower-middle elevations.
Race Timeline
8:00 AM: 59 degrees in City of Norton with fog or low cloud bases ( or a fog layer just above downtown ).
Low-mid 50s in cooler high valleys of the High Knob Massif.
60 to 62 degrees at the summit level of High Knob with breezy S-SW winds. Chance of low clouds & dense fog.
10:00 AM: 63 degrees in Downtown Norton with a fog layer or breaking low cloud base above the city.
63 to 65 degrees at summit level of High Knob with partly cloudy skies as fog layer begins breaking on light to breezy S-SW winds.
A mixing layer in between downtown Norton and the summit level will be marked by fog that is beginning to break up and dissipate. Air flow along the massif will be undergoing transition (change) from nocturnal mountain (downslope) to daytime valley (upslope) air flow with increased vertical mixing.
This period can sometimes result in rapid vertical cloud development over the massif, and trigger showers, but with some luck localized shower or thunderstorm development will hold off until after the race is over ( however, this has to be noted and kept in mind ).
12:00 NOON: 76-78 degrees in Norton with partly cloudy skies. Light S-SW winds.
68 to 70 degrees at summit level of High Knob with partly cloudy skies ( vertically building clouds ). Light to breezy S-SW winds.
Unseasonably mild conditions will return to dominate the next 1-2 weeks, with another trend toward above average precipitation developing as well during this extended 5-10+ day range ( remember that October is climatologically the driest month of the year ).
The anomalous warmth of September is exemplified by a 68.5 degree average daily maximum on Eagle Knob of the High Knob Massif, which just beat the 68.4 degree average daily max observed during August!
How often are average September high temperatures warmer than August? A question to be researched, but a quick look through the Wise database from 1955 to 2012 reveals NONE. NADA. No year had a September with warmer mean highs than August!
Signs of a major pattern change are beginning to show up in the far extended range, by mid-late October into November as a late developing, central-Pacific based El Nino ( +ENSO ) continues to form and exerts more influence upon the synoptic-scale flow fields across the Northern Hemispere ( along with other factors ).
Overnight Into Monday Morning
Partly cloudy then increasing clouds toward morning. Areas of dense valley fog. Winds S-SW at 5-10 mph with higher gusts on mid-upper elevation mountain ridges. Temps varying from lower 50s to the low 60s ( coolest in mountain valleys at upper elevations ).
Monday Afternoon
Partly-mostly cloudy. Chance of hit-miss showers and thunderstorms. Light SSW to SW winds generally less than 10 mph. Temperatures varying from mid-upper 60s to the mid-upper 70s ( coolest in upper elevations ).
Monday Night Into Tuesday Morning
Mostly cloudy. Chance of a shower. SW-W winds 5-10 mph with some higher gusts on mid-upper elevation mountain ridges. Temperatures in the upper 50s to middle 60s. Areas of valley fog.
Tuesday Morning Through The Afternoon
Chance of showers & thunderstorms. SW-W winds 5-15 mph, with some higher gusts on mountain ridges. Temps varying from the 60s to the middle 70s ( coolest in upper elevations ).
Tuesday Night Into Wednesday Morning
Partly-mostly cloudy. Chance of a shower. Areas of dense fog. Winds WSW-WNW at 5-10 mph on mid-upper elevation mountain ridges. Temperatures varying from the middle 50s to the middle 60s.
Reference the High Knob Hellbender 10K section for a forecast specifically designed for this race in coming days ( my Cloudspitter 100 forecast will be featured during coming weeks in advance of this race ).
Weather Discussion ( More Of Same )
A brief cooling trend which came just in time for the 12th Annual High Knob Naturalist Rally will become a memory through coming days.
High Knob Lake Recreation Area – High Knob Naturalist Rally 2018
A buoy line can be seen across the lake in the far distance to keep kayaks and canoes safely away from the overflowing High Knob Lake Dam. Up to 3.50″ of rain were reported in the area immediately prior to the Naturalist Rally.
Temperatures in the 50s to lower 60s were observed during the time of this year’s High Knob Naturalist Rally ( 7:00 AM to 5:30 PM below ), with morning low clouds and fog slowly giving way to some welcomed afternoon sunshine.
Eagle Knob of High Knob Massif ( Time UTC )
Temperatures in the 50s during much of the rally were in rather dramatic contrast to 70s-lower 80s in the Tri-Cities, with some visitors seen shivering ( and talking about the chill ).
Beautiful Water Flowing Into High Knob Lake – 2018 Naturalist Rally
Mean averages during the next week to 10 days will be lower given decreasing sun angles, but nothing close to reality for this point in the year ( see graphics below ).
Approaching Sunset – Upper Norton Reservoir – September 29, 2018
While trees are changing again in spurts, the combination of atypical mildness + a lack of frost + anthracnose fungi impacts are making it slower and duller so far. The final result yet to be determined; however, clearly these ingredients are far from ideal and have already caused some significant leaf drop ( especially at the higher elevations above 3500 feet ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
A deepening western USA upper trough will turn flow more S-SW across the eastern USA over time, renewing the above average precipitation pattern.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
While some signs of a major change are beginning to show up in the far extended range, the next 1-2 weeks are looking anomalously mild at this present time.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5
Warm anomalies in the 6-10 day range ( below ) increase due to both a combination of deeper southerly flow from the tropics and to climatology, given temperatures should be declining ( in the mean ) moving through October.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 6-10
This could be setting the region up for a HUGE temperature crash once a change finally occurs, and this pattern flips from current upper air ridging into upper troughing.
An ALERT for redevelopment of low clouds and dense fog overnight through Saturday Morning.
Abundant low-level moisture will support dense fog formation, and low clouds, through the overnight into Saturday morning. Caution is advised for travelers.
Former ALERT
ALERT Continues For High Water Levels On Creeks Draining The High Knob Massif Into Friday Afternoon
As of 9:00 AM ( September 28 ) Big Stony Creek was dropping from an overnight crest of around flood stage, with a continuation of ROARING water levels.
Significant overflow had developed at Big Cherry Dam with ROARING water levels on South Fork of Powell River ( which remained below flood stage ).
Caution is advised along & downstream of these steep creeks for swift water and slick banks, this includes Little Stony Creek and numerous others along the Wise-Scott border area, through Friday.
Big Stony Creek of High Knob Massif
At 9:00 PM Thursday creeks were near flood stage, with around 3.00″ of total rainfall during this event at upper elevations in the High Knob Massif. Caution Is Advised in locations along and downstream of these roaring creeks.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Wednesday Night Into Thursday Morning
Humid with a chance of rain showers. Thunder possible. Low cloud bases with areas of fog, dense at times, especially above 2500 to 3000 feet. Winds NW to NE at 5-10 mph, with some higher gusts. Temperatures dropping into the upper 50s to middle 60s.
Thursday Morning Through The Afternoon
Cloudy with periods of rain. Thunder also possible. Local downpours. Variable winds at generally less than 10 mph. Temperatures from around 60 degrees ( highest elevations ) to mid 60s to 70 degrees. Low cloud bases. Areas of fog, dense at upper elevations.
Thursday Night Into Friday Morning
Showers. A chance of thunder. Downpours possible, especially during the evening. Winds WNW-N at 5-15 mph, with higher gusts. Areas of fog, widespread and dense at upper elevations. Temperatures falling through the 50s, with 50-55 degrees at high elevations.
Friday Morning Through The Afternoon
A chance of drizzle or local showers. Partly-mostly cloudy. Winds NW to NE at mainly less than 10 mph. Temperatures varying from upper 50s to the upper 60s.
Friday Night Into Saturday Morning
Chance of drizzle, low clouds and fog redeveloping, dense and widespread fog above 2500-3000 feet. NW-N winds at generally less than 10 mph. Temperatures in the 50s, with upper 40s to low 50s in cooler mountain valleys.
Saturday Morning Through The Afternoon
Low clouds with areas of dense fog and possible drizzle through the morning. Rising cloud bases with breaks by mid-late afternoon. Light NNE-ENE winds. Temperatures in the mid-upper 50s to mid-upper 60s.
High Knob Naturalist Rally ( Sept 29 )
Looking Across High Knob Lake Basin – September 22, 2018
High Knob Naturalist Rally Forecast
Dense fog and low clouds over saturated ground is expected to be present through the morning, followed by rising cloud bases with breaks to partly cloudy skies during the afternoon.
Conditions will remain cool on light NNE-ENE winds. Temperatures will mainly be in the 50s at High Knob Lake ( be sure to dress for chilly conditions ) and may rise above 60 degrees if sunshine becomes abundant.
Friday – September 28 Temperatures at High Knob Lake
*University Of Virginia’s College At Wise Research Station National Weather Service calibrated temperature sensor ( Data Period: November 19, 2016 to Present )
*The average daily maximum during September 1-22 was nearly as warm as observed during July ( 73.7 degrees ), much above average for this time of year, and was warmer than the average summer maximum at High Knob Lake in 2018 ( 72.4 degrees ). The highest summer temperature reached 80.9 degrees ( 150 total minutes at or above 80 degrees during 2018 at High Knob Lake ).
A seemingly endless summer weather pattern is expected to continue through this week, and perhaps through the first week of October, per the latest trend of the European 51-member ensemble mean. The only exception being a brief period with notably cooler air this weekend, just in time for the Naturalist Rally!
Some of the coolest air will be Saturday into early Sunday as northerly upslope flow helps to bring a touch of autumn to the high country just in time for the Naturalist Rally.
Unfortunately, for those looking for true autumnal chill that will last it is just not in the cards. Not yet.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
The only change in the short-term is a small drop in heights and minor weakening of the upper ridging before it builds back again.
The latest trend in the 6-10 day ( below ) is to maintain anomalous upper air ridging over the eastern USA to keep temperatures running well above average.
Note that significant chill at this time of year would be that which features mountain valley frost and freezes, especially in the high country. While air will cool some in upcoming days it will not be anything like typical for this time of year and may not be able to equal what has already been observed in August ( frost occurred during August 24 in Alder Swamp of Dolly Sods, Wv., where the lower dewpoint air was able to do its thing with drainage ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
This type of upper air pattern equates to much above average warmth for this time of year, with any cooler air in coming days being short-lived as a boundary stalls and lifts back northward once again.
European Model 850 MB Temperature Anomalies Forecast: Days 1-5
While most of Alaska has shifted back to unseasonable warmth ( above ), the bulk of Canada has turned chilly.
Significant changes are being noted in the 6-10 day range ( below ), with cold air building and pooling along the eastern side of the northern Rockies ( but with weaker anomalies than forecast a week ago ).
European Model 850 MB Temperature Anomalies Forecast: Days 6-10
This latest trend will shear away cold air building along the eastern side of the northern Rockies as it slides southeast into a rebounding upper air ridge.
Eventually, chilly air in Canada will be able to spread southeast but perhaps not until the second week of October? Stay tuned for updates.
Wetness Continues
High Knob Lake on September 22, 2018
*Cloud bases were engulfing highest ridges at the time this view was captured, with bases soon dropping to also engulf High Knob Lake Basin where every September day has featured RH-Dewpoints which have reached saturation. A trend observed during much of this growing season and likely responsible, at least in part, for Anthracnose fungal infections impacting many tree species at upper elevations ( especially maples and northern red oaks ).
Continued warmth will also support an above average rainfall trend, with showers & downpours in thunder-storms increasing in coverage. Again, the potential for locally heavy to excessive rainfall will need to be monitored through upcoming days.
Although heaviest rains with Florence remained to the east, September has been another wet month with 22 of the past 24 days featuring measurable rain in the official rain gauge at the City of Norton Water Plant.
This boosted 2018 precipitation to 55.59″ ( M ) with a general 59.00″ to 66.00″+ in upper elevations across the high country of the High Knob Massif.
( M ) = Missing moisture during February with a rain gauge spill.
Recap of Florence Rainfall Totals
A general 1.00″ to 3.00″ fell along the Cumberland Mountains, with much heavier amounts to the east and southeast ( as expected ).
Mount Mitchell SP: 14.32″
Meadows of Dan 5 SW: 7.99″
Whitetop Mountain: 7.08″
Boone NWS Cooperative: 6.22″
Grayson Highlands SP: 5.70″
NWS Precipitation Analysis During September 14-21
Although rainfall totals came in within or very close to the ranges on my forecast graphic they were held down somewhat by a more northerly turn of the low center, which tracked east of the official NHC track and model mean. This especially impacted the south-western portions of the mountain chain, where only 1.44″ were measured at Newfound Gap and 3.10″ on Mount LeConte ( atop the Great Smokies ). That was the big error on my graphic, with the 14.32″ not far away on Mitchell being on target ( illustrating how minor track changes can create a huge difference ).
Compare the NHC Official Forecast Track:
National Hurricane Center Official Forecast Track For Florence
To the Actual Inland Path followed by Florence:
Actual Florence Track Plotted On Google Earth
The Great Smokies and most of the High Knob Massif were to the left ( west ) of the track center. Heaviest rains fell mainly east of the track line. This created huge rainfall differences ( 11.22″ ) between Mitchell and Mount LeConte ( 14.32″ versus 3.10″ ).
*Weather stations on Mount Mitchell ( 6240 feet ) and Mount LeConte (6400 feet ) are only different by 160 vertical feet.
They are radically different; however, with respect to air flow trajectories and mean prevailing winds in terms of orographic forcing. The track difference with Florence illustrated this.
*A general 2″ to 4″ of rainfall is currently expected across much of the Cumberland Mountains. Greater totals will also be possible at upper elevations. Strong water levels rises will occur and flooding can not be ruled out should totals end up near, or above, the higher end of this forecast range.
Rainfall Totals During September 15-18 Period
*Flooding rainfall amounts are expected along and east of the Blue Ridge province, with widespread totals of 4″ to 10″ . Locally heavier amounts, with potential for up to 18″+ will be possible at higher elevations along the Blue Ridge ( e.g., Grandfather Mountain and Mount Mitchell ).
Lesser 1″ to 4″ rainfall amounts are expected across adjacent zones, with locally higher amounts possible at upper elevations in the Cumberland Mountains.
A chance of showers & thunderstorms Saturday will give way to increasing wind-rain into overnight hours of Saturday-Sunday as the remnants of Florence begin impacting the Mountain Empire.
Florence is currently beneath a weak wind field, but is expected to begin moving fasting in coming days. This motion will be critical to rain amounts as noted below.
Orographic forcing will be a factor with enhanced rain amounts on windward slopes-crests. The current forecast track will generate inflow changes over time, complicating the rainfall forecast over mountainous locations within the Mountain Empire.
*NOTE that eventual rain amounts will be dependent upon the speed of movement of these remnants, with slower movement generating heavier amounts than forecast and an acceleration resulting in lesser amounts than currently forecast.
Stay tuned to NOAA Weather Radio and your favorite media sources for updates on Watches and Warnings which will be issued during this evening.
