Mostly clear ( high clouds ) and cold. Large vertical temperature difference between colder mountain valleys & exposed middle-upper elevation mountain ridges-plateaus. Variable winds generally less than 10 mph on ridges. Calm valley winds. Temperatures varying from low-mid 20s in the colder valleys to the mid-upper 30s to near 40 degrees on exposed mountain ridges.
Saturday Afternoon
Partly-mostly sunny with high clouds. Light winds. Temps varying from the upper 50s to low 60s at upper elevations to the upper 60s to lower 70s.
Saturday Night Into Sunday Morning
High clouds. Large vertical temperature spread developing between sheltered valleys and exposed mountain ridges and plateaus. Winds SSE-SSW at 5-10 mph, with higher gusts, on exposed mid-upper elevation mountain ridges-plateaus. Temperatures varying from upper 20s to mid 30s in valleys to the mid-upper 40s on exposed mountain ridges.
Sunday Afternoon
Becoming mostly cloudy. Small chance of a rain shower. Seasonally cool. SE-S winds 5-15 mph with some higher gusts on mountain ridges. Temperatures varying from the lower 50s to the lower-mid 60s ( coolest highest elevations.
Sunday Night Into Monday Morning
Cloudy & windy. Chance of rain showers by morning. SE-SSE winds 10-25 mph, with higher gusts. Temperatures mainly in the 40s to around 50 degrees ( falling to near 40 degrees at highest elevations ).
Weather Discussion ( Chilly Pattern )
Frosty cold conditions were developing in mountain valleys late Friday night into the early hours of Saturday as a chilly pattern continues for this time of year.
Mid-Spring Snow In High Knob Massif – April 16, 2018
Although large temperature swings have occurred during the past week, the general pattern continues to be cooler than average for mid-spring.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
Upcoming days will continue to feature near to below average conditions through the end of April, with a trend on the European Ensembles toward cooler conditions in the final days of this month ( it would not be impossible that more April snowflakes fly, at least at high elevations ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
Coolest conditions in the next few days will occur along the eastern slopes of the Appalachian chain, on SE flow, before a shift back to the western side of the Appalachians occurs with a return of westerly to northwesterly flow. This period will also feature periods of rain and showers.
GFS Ensemble Mean Total Precipitation Forecast – Next 10 Days
ALERT For Strong To Roaring SW Winds Overnight Through Friday PM In The Cumberland Mountains
A strong pressure gradient in advance of the next storm system developing over the central United States will generated strong ( roaring ) SW winds through April 13.
Lonesome Pine Airport In Wise
Winds will be especially strong at mid-upper elevations and within mountain wave breaking locations along and north to northeast of the High Knob Massif and Black Mountain in northern portions of Wise-Dickenson counties ( in surges ).
ALERT For Accumulating Snow Mainly At Mid-Upper Elevations Through Early Monday Morning – Locally At Elevations As Low As 1500 Feet Along & North Of The High Knob Massif
Heavy Snow On Eagle Knob of High Knob Massif
Update At 5:30 AM Monday – Snow is falling heavy enough to begin sticking with temps above freezing in Clintwood, with roadways now covered at upper elevations within the High Knob Massif where temperatures are in the 20s.
Some slick travel will be possible on higher elevation roads, especially those that cross through terrain above 3000 feet, but due to the snowfall rates some brief slushy travel will also be likely at elevations below 3000 feet.
University Of Virginia’s College At Wise – Accumulating Snow
A upper air disturbance will be crossing the mountains into Monday with another round of snow. Most significant amounts are expected at elevations above 3000 feet, with lesser totals in middle elevations between 2000-3000 feet. Limited sticking is expected below 2000 feet. Due to the timing of heaviest snow, snowfall rates could be highest around-before AM commutes.
Snowfall Forecast – Monday AM ( April 9 )
1″ or less at elevations below 3000 feet
1″ to 2″ at elevations above 3000-3500 feet
Locally higher amounts are possible at highest elevations where air temperatures have been coldest ( generally near or below freezing during the weekend ).
Sunday Night Into Monday Morning
Lowering and thickening clouds with a rain-snow mix and snow developing during the predawn-morning. A period of moderate to heavy snow will be possible, especially at mid to upper elevations. Light NE surface winds to breezy SW winds highest elevations. Temps varying from the 20s to low-mid 30s.
Monday Morning Through The Afternoon
Morning snow giving way to a chance of light rain showers. SW winds shifting NW by late at generally 10 mph or less. Temps varying from 30s in upper elevations to the mid-upper 40s ( milder to the south into the Great Valley ). Orographic clouds ( dense fog ) at highest elevations.
Monday Night Through Tuesday Morning
Mostly cloudy. Chance of flurries, especially at upper elevations in the High Knob Massif, then becoming partly cloudy into morning. NW-N winds 5-10 mph with some higher gusts. Temperatures in the 20s to low-mid 30s, coldest at upper elevations. Wind chills in the 20s to low 30s, except 10s at highest elevations.
Tuesday Afternoon
Partly cloudy. Seasonably chilly. NW winds 5-10 mph. Temperatures varying from upper 30s to low 40s in upper elevations to the upper 40s to low-mid 50s ( milder south into the Great Valley ).
Tuesday Night Into Wednesday Morning
Mostly cloudy, then becoming partly to mostly clear by morning. Light WNW-NW winds. Temperatures varying from low-mid 20s in mountain valleys to the low-mid 30s, locally colder within high valleys of the High Knob Massif.
A warmer and more active spring rain-thunderstorm pattern is being monitored for late this coming week into RACE Weekend at Bristol. Stay tuned for later updates.
Weather Discussion ( Winter Lingers )
Monday Evening Update
A wintry morning in April greeted your Monday as snow fell briskly from the predawn through the post-sunrise period.
Eagle Knob of High Knob Massif at 7:09 AM – April 9, 2018 ( Moderate-Heavy Snow )
The greatest snow amounts occurred in upper elevations of the high country, with up to 0.28″ of water equivalent reported at both Big Cherry Lake Dam and on Eagle Knob ( 2-3″ of snow ).
To the east, Joe Fields measured 1″ of snow on the ground in the High Chaparral community at 8:30 AM. Amounts were generally less than 1″ at elevations below 3000 feet ( 0.5″ depth Clintwood ) with 0.6″ ( 0.06″ water equivalent ) reported by Wayne & Genevie Riner on Long Ridge of Sandy Ridge up to observation time.
Long Ridge In Dickenson County At 8:52 AM – April 9, 2018
I think humans and ALL Creatures Great & Small will certainly welcome true Spring when it finally arrives to stay this year, as the Ole Man Of Winter is beginning to ”wear out his welcome.”
University Of Virginia’s College At Wise
Snow melted away relatively fast in Wise but lingered throughout the day, beneath some nice mountain waves, along northern slopes at upper elevations.
*This latest event brings the days with 1″ or more of snow depth to 11 weeks for the 2017-18 winter season on northern slopes at the upper elevations in the High Knob Massif ( High Knob Lake Basin ).
While a few snow flurries are falling on High Knob tonight, the main focus through Wednesday will just be cold temps with mountain valleys experiencing another hard freeze during Tuesday Night into Wednesday AM.
Previous Discussion
Winter conditions will linger for a few more days before a major pattern change introduces a warmer spring-storm regime by late in the upcoming week-next weekend.
High Knob Massif Webcam – University Of Virginia’s College At Wise
An unseasonably cold Sunday morning for April greeted the mountain landscape with temperatures varying from 10s at upper elevations to the 20s ( 22 degrees in Clintwood ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
Sunday remained so cold that extensive rime covering the high country of the High Knob Massif was actually able to linger throughout the daylight hours at highest elevations ( with snow on northern slopes ).
Quite a feat, indeed, for early April given that the Noon Solar Angle over the High Knob peak is now 61.1 degrees.
A solar angle of 61.1 degrees above the horizon at noon means that insolation ( incoming solar radiation ) is being spread across 1.14 units of surface area to generate a solar intensity of 87.5 percent of what it would be if the sun were directly overhead ( * ).
*The sun is NEVER directly overhead outside the tropics ( 23.5 degrees N to 23.5 degrees S ) and reaches a maximum over the High Knob peak during the Summer Solstice when the noon solar angle is 77.0 degrees ( June 21 ).
At that time insolation is spread across 1.026 units of surface area to generate a solar intensity of 97.4% of what if would be if the sun were directly overhead. Although MAX solar intensity occurs in June, due to seasonal lag-time forced by the slower accumulation of heat by surfaces the MAX in mean annual temperature typically does not occur until July. Interestingly, in the High Knob Massif, highest annual temps sometimes occur during Spring, prior to full leaf maturation, as clouds become so abundant during Summer that insolation is increasingly blocked.
European Model 850 MB Temp Analysis At 8 AM Sunday – April 8, 2018
The Sunday morning 850 MB temperature analysis from the European Model certainly showed this unseasonable April cold, and the anomalies ( below ) associated with it.
European Model 850 MB Temp Anomalies At 8 AM Sunday – April 8, 2018
Looking ahead this eastern USA trough will be replaced, at least for a short time, by ridging forming in advance of an upper wave that is looking increasingly potent on forecast charts by late this coming week into the weekend.
European Model 51-Member Ensemble Mean 500 MB Anomalies: Days 4-8
The focus in coming days will be on this wave and whether or not it does intensify to develop a negative tilt or if the wave maintains a positive tilt ( the former = a much more potent system ). Significant rain and thunderstorms could result amid an increasingly large temperature gradient if the wave undergoes significant amplification ( since cold air will remain abundant to the north across Canada ).
More cold air, and perhaps even more snow, will be possible if this upcoming wave amplifies significantly by around the April 15-16 period ( way out in time and merely speculation at this point, so check back for updates ).
Unseasonably Cold Conditions Will Continue Through Sunday In Wake Of A Wintry Saturday
Eagle Knob of High Knob Massif – Early Evening of April 7, 2018
Although a little snow stuck to roads at highest elevations, and the graveled lots, most of the 1″ to 2″ of accumulation was in the woods, on grass and above ground objects ( with rime formation on trees ).
A snowfall total of 1.2″ was officially measured in Clintwood during this late season event ( 1″ being the maximum depth ).
Former Alert
ALERT For Significant Snowfall Developing During The Predawn-Morning Hours Of Saturday ( April 7 )
A wave of low pressure following what is a climatologically favored track for significant snowfall will be developing by late Friday into Saturday, with rain changing to heavy, wet snow. While the most significant accumulations are likely at mid-upper elevations, the combination of recent cold and fast falling snow is expected to present a hazard across the area, especially in locations beneath upslope flow on NW-N air flow trajectories along & north of the High Knob Massif and Tennessee Valley Divide.
Snowfall Forecast – Saturday Into Saturday Evening
General 1″ to 3″ at elevations below 3000 feet in locations along and north of the High Knob Massif-TN Valley Divide
Target Snowfall of 2″ ( +/- ) 1″ for Norton-Wise. This implies the potential for 1-3″ of snowfall within the 2000-3000 foot zone.
Locally higher amounts possible above 3000 feet.
There is currently a low-moderate chance that snowfall could be heavy enough to cause power outages, so please check back for a update as the storm track and intensity becomes more certain.
Overnight Into Friday Morning
Partly cloudy ( high clouds ). Windy across ridges. SW winds 5-15 mph, with higher gusts, along mountain ridges and plateaus below 2700 feet. SW winds 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temps varying from 20s to low 30s in sheltered valleys to the low-mid 40s on exposed middle elevation ridges-plateaus.
Friday Afternoon
Becoming cloudy with a chance of rain showers by late. SW winds 10-20 mph with higher gusts. Temperatures varying from low-mid 40s in upper elevations to the mid-upper 50s to around 60 degrees ( downslope locations ).
Friday Night Into Saturday Morning
Rain, heavy at times. Turning colder. Rain changing to a mix or snow into the predawn-morning. SW winds shifting NNW-NNE at 10-20 mph with higher gusts. Temperatures dropping into the 20s to lower 30s, especially in locations along and north of the High Knob Massif-Tennessee Valley Divide. Wind chills dropping into the 10s and 20s, except colder at highest elevations.
Saturday Morning Through The Afternoon
Cold & gusty with snow showers and snow, especially in the mid-late afternoon. Winds N-NNE at 5-15 mph with higher gusts. Temps varying from the lower 20s to the lower 30s in locations along & north of the High Knob Massif-Tennessee Valley Divide. Milder to the south into the Great Valley. Low clouds with riming at the highest elevations.
Saturday Night Into Sunday Morning
Evening snow showers & flurries giving way to clearing skies and diminishing valley winds. Unseasonably cold. Winds NW-N at 5 to 10 mph, with higher gusts, along the middle-upper elevation mountain ridges. Temps dropping into the low 10s to low-mid 20s ( coldest upper elevations ). Wind chills in the single digits and 10s, except colder in gusts at highest elevations.
Sunday Afternoon
Increasing mid-high altitude clouds. Light NW-NE winds. Temperatures varying from 30s at upper elevations to the 40s at lower-middle elevations ( especially along-north of the High Knob Massif-Tennessee Valley Divide ).
A major pattern change into Spring is being tracked for next week, with an increasing threat for strong-severe thunderstorms by late next week-weekend ( possible squall line ahead of a negatively tilted upper-air trough ). Stay tuned for later updates.
Weather Discussion ( Heavy Snow? )
Early Overnight ( Saturday ) Update
Forecast models continue to struggle with this system, with the European Model group solution being followed since it has been most consistent during the past couple days.
If the European Model solution holds, a low pressure will track south of the area and be over South Carolina by 8:00 PM Saturday, placing the Cumberland Mountains in northerly upslope flow and generating the best conditions for snowfall during the mid-late afternoon into the evening prior to clearing skies into Sunday.
Previous Discussion
Although forecast models have struggled to pinpoint this system, a clear southward trend has occurred during the past 24-36 hours with a mean track that now is fitting past climatology of heavy snow producing systems within the High Knob Massif area. Will this trend hold? Check back for an update into Friday night.
*Winter Storm Watches to the north may need to be moved south, as the heaviest snowfall is looking more likely across the higher terrain of the southern-central Appalachians.
Bloodroot ( Sanguinaria canadensis ) – April 5, 2018
Bloodroot, with a distinctive leaf ready to curl around it’s lovely bloom, has been covered many times in spring by snowfall in the mountains ( it is now blooming at low-middle elevations along & north of the High Knob Massif, and has been blooming, or even past bloom, in milder locations toward the southwest & south ).
European Model 850 MB Analysis At 8:00 AM Thursday – April 5, 2018
Ideal cooling conditions beneath High pressure allowed temperatures to drop into the 10s amid high valleys and along highest mountain ridges in the High Knob Massif during morning hours of April 5. An official minimum of 24.6 degrees was recorded in Clintwood ( the air temp had dropped back to a frosty 30 degrees at 3:50 AM Friday ).
GFS Model Total Snowfall Forecast Through Saturday
Models clearly have some work to do yet before they come into agreement, with the European Model and the mean of its cluster currently being closer to the GFS Model than to the NAM Model ( the 00z April 6 run ).
NAM 12 KM Model Total Snowfall Forecast Through Saturday
So the BEST option at this present time is to look at the storm track versus past climatology and to use that as a strong bias, the result suggesting that the NAM will be increasing its output of snow in coming runs to fit what similar tracks in the past have generated ( thus, potential exists that total snowfall may be heavier than currently suggested and this will need to be updated late today into tonight ).
Strong-Severe Wind Gusts Recorded With Squall Line
Flatwoods Mountain Mesonet
A severe 70 mph wind gust was recorded just prior to 2:00 AM on April 4 by the Flatwoods Mountain Mesonet, adjacent to Pine Mountain, in extreme southeastern Pike County, Ky., near the Pike-Dickenson County border.
Black Mountain Mesonet
A 52 mph gust, with many gusts at or above 40 mph, was recorded by the Black Mountain Mesonet in Harlan County, Ky., adjacent to the Wise-Harlan line on the VA-KY border.
GOES-16 Image At 2:02 AM on April 4, 2018Lightning Detection With Shortwave IR At 2:02 AM on April 4, 2018
Former Alerts
Severe Thunderstorm Watch Number 34 Is In Effect
Storm Prediction Center Severe Thunderstorm WatchSPC Severe Thunderstorm Watch Statement
ALERT For Strong SW Winds Developing Late Tuesday Into Tuesday Night Well In Advance Of A Squall Line
A strengthening pressure gradient will increase winds across the mountain area Tuesday afternoon into Tuesday night in advance of a developing line of strong to severe thunderstorms forming west of the Appalachians.
Storm Prediction Center Updated Risk Regions Into Early Hours of April 4
Locally strong to severe wind gusts will also be possible along the squall line that should be in a weakening mode as it crosses the mountains after midnight Wednesday, with a sharp temperature drop expected into Wednesday morning.
Frosty cold conditions are expected into Thursday morning.
Overnight Into Tuesday Morning
Cloudy. Areas of dense fog. A chance of scattered rain showers. SW winds 10 to 20 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures in the 40s to lower 50s.
Tuesday Afternoon
Partly to mostly cloudy. Chance of hit-miss showers and thunderstorms. Windy. SSW-SW winds 10-20 mph with higher gusts. Temperatures varying from low-mid 60s to low-mid 70s ( coolest at upper elevations ).
Tuesday Night Into Wednesday Morning
Showers & thunderstorms becoming likely, especially overnight. Windy. SSW-SW winds 15-25 mph, with higher gusts, shifting WNW by morning. Turing sharply colder by morning. Evening temperatures in the 50s and 60s, then plunging rapidly into the 30s to low 40s by morning…with upper 20s to around 30 degrees at highest elevations. Wind chills dropping into the 20s & 30s by morning, with 10s in gusts at highest elevations.
Wednesday Morning Through The Afternoon
Morning clouds giving way to partly-mostly cloudy skies. Windy & seasonally cold. WNW-NW winds 10-20 mph with higher gusts. Temperatures varying from 30s in the upper elevations to the 40s at low-middle elevations ( milder lee of the Cumberland-Allegheny Front ).
Wednesday Night Into Thursday Morning
Becoming mostly clear with decreasing NW-N winds. Frosty cold. A hard freeze within mountain valleys. Temperatures falling into the 20s to near 30 degrees, except 10s in colder mountain valleys at upper elevations.
A colder than average weather pattern for this time of year is expected to continue into next week. A system with the potential to produce significant snow is being monitored for this weekend.
Weather Discussion ( Active Pattern )
An active spring weather pattern will continue through coming days, with a notable trend toward colder-than-average conditions for this time of year.
Temperatures held in seasonally chilly 40s to lower 50s through Monday in locations along and north of the High Knob Massif and Tennessee Valley Divide. By Wednesday temperatures will be even colder despite a developing mix of sunshine and clouds.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Although early spring wildflowers are beginning to bloom, especially at lower-middle elevations, a up-and-down temp pattern is typical for this time of year…as is snow.
Yellow Trout Lily ( Erythronium americanum ) – Early Spring 2018
While beginning to show signs, very little is currently blooming at upper elevations in the High Knob Massif where the colder valleys recently dropped into low-mid 10s during March 22 and the lower-middle 20s during March 31 ( the last 0 degree reading occurred in early February ). Another morning with MIN temperatures into the 10s is upcoming into April 5.
Big Cherry Lake of High Knob Massif – March 31, 2018
This forecast period ( April 2-5 ) 31 years ago featured a historic snowstorm during 1987, with a general 2 to 4 FEET of snow depth along and north of the High Knob Massif.
Re-Analysis Chart For April 4, 1987
Carl Henderson, electrical engineer for the Blue Ridge PBS transmitter station on Eagle Knob reported a general 2 to 6 feet of snow depth by the conclusion of this great storm.
Nearly 2000 vertical feet below, in the City of Norton, a snow depth of 3 feet was reported by Gary Hampton at the Norton Water Plant this week in April 1987.
The short-term forecast will focus on increasingly strong winds and the potential of wind damage, locally in pressure gradient driven flow late Tuesday into Tuesday night, then along a squall line of showers-thunderstorms into the over-night and predawn hours of Wednesday.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 4-8
While the short-term will focus on a windy, warm surge of air Tuesday ( March 3 ) that will support formation of severe thunderstorms west of the Appalachians by the afternoon, medium range attention quickly shifts to a colder than average pattern that has the chance to generate some significant snowfall by this weekend.
European 51-Member Ensemble Mean 850 MB Temp & Anomalies: Days 4-8
A mean 850 MB temperature around 32 degrees F ( 0 C ) is being forecast by the European Model Ensemble MEAN in the upcoming 4-8 day period during April 6-10. This chilly period begins, as noted in the forecast, by Wednesday AM and features frosty cold 20s by Thursday AM ( with 10s in colder valleys of the High Knob high country ).
While there are signs the pattern may trend milder during the second half of April, up-down temperature fluctuations are likely to continue into May ( as climatology shows ).
Although The Threat Of Widespread High Water Has Decreased, Downpours Later Thursday Into Friday Should Still Be Monitored For The Possibility Of Localized Water Level Rises & Ponding
Overnight Into Thursday Morning
Mostly cloudy. Mild. S to SW winds 5-15 mph with higher gusts along mid-upper elevation mountain ridges-plateaus. Temperatures in the 50s to near 60 degrees.
Thursday Afternoon
Mostly cloudy and unseasonably warm. Chance of a shower or thunderstorm. S-SW winds 10-20 mph with higher gusts. Temperatures varying from the low-mid 60s to the low-mid 70s ( coolest in upper elevations ).
Thursday Night Into Friday Morning
Showers & thunderstorms developing. Downpours likely. Gusty SW winds shifting NW-NNW at 5-15 mph, with higher gusts. Turning colder overnight into morning with temps dropping into the 30s to mid-upper 40s ( coldest at upper elevations ). Wind chills dropping into the 30s to low 40s, with 20s at highest elevations.
Friday Morning Through The Afternoon
Mostly cloudy, damp, and chilly with a chance of showers and drizzle. Mixed precipitation or snowflakes possible at highest elevations. Widespread low clouds-fog at the upper elevations. Temps holding near steady or falling in the 40s at low-mid elevations, and the 30s at upper elevations, in locations along and north of the High Knob Massif and Tennessee Valley Divide. Wind chills in the 20s & 30s.
An unsettled weather pattern is expected to continue into April with more significant precipitation likely amid the return of cooler than average conditions.
Weather Discussion ( Close Call )
Although some light showers have occurred during the past 24-hours, high pressure off the southeastern USA coast has been just strong enough to hold training batches of heavier rainfall west of the mountains in the Kentucky foothills.
One aspect not being under-estimated has been wind, with gusts topping 30-40 mph ( especially across upper elevations ) during the past several days & nights. This has kept the atmosphere well mixed and relatively mild for late March.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Rather extensive snow continued to cover upper elevations in the high country, especially northern slopes, throughout March 27.
Downpours are still expected as the front approaches the mountains by Thursday Night into early hours of Friday, but duration of heavy rain should be limited within the maritime tropical air mass ahead of the cold front.
Given recent snow melt and wet conditions strong rises may still occur on streams, so please remain alert.
NAM 3 KM Model Temperature Forecast At 4:00 PM Friday – March 30, 2018
A modified cP ( continental Polar ) air mass will be pouring into the mountains Friday, and if low clouds hold tough the conditions will become extremely chilly with 30s and 40s in locations along and west-northwest of the Cumberland and Allegheny Front ( with colder wind chills ).
ALERT For Strong SSW To WSW Winds At Mid-Upper Elevations From Tuesday Through Wednesday
A strengthening pressure gradient will support strong and gusty SW winds into the Cumberland Mountains, especially at higher elevations, from Tuesday through Wednesday.
Downpours In Showers And Possible Thunderstorms Will Become Likely Wednesday Through Thursday, In A Pattern Conducive To Training And The Orographic Enhancement Of Rainfall Along And Westward From The Cumberland Mountains
Those living and driving along creeks and in low-lying, flood prone locations will need to be alert for the potential of strong water level rises, especially in locations along and west of the Cumberland Front where orographic rainfall enhancement will be favored over already wet ground.
*Thursday ( March 29 ) is looking like the day with best support for heavy rainfall. If rainfall amounts remain limited and west of the mountains into Thursday it will help but not eliminate the threat. Models currently disagree on how much rain will fall with this system, despite climatologically favored air flow trajectories.
Overnight Into Monday Morning
Mostly cloudy. Windy across mid-upper elevation ridges and exposed plateaus. SE winds 10-25 mph, with higher gusts. Temperatures varying from the upper 20s to the mid-upper 30s. Winds chill factors in the 20s to low 30s, except 10s in gusts at highest elevations.
Monday Afternoon
Mostly cloudy. Gusty. Winds SE-S at 5-15 mph with higher gusts. Temperatures varying from the mid 40s to the mid-upper 50s ( coolest upper elevations and warmest within downslope locations along & northwest-north of the High Knob Massif and Tennessee Valley Divide ). Wind chills in the 30s at the highest elevations.
Monday Night Into Tuesday Morning
Mostly cloudy. Chance of rain showers. Windy. SE-S winds at 10-20 mph, with higher gusts, along mountain ridges and plateaus below 2700 feet. SSE-SW winds 15-30 mph, with higher gusts, on mountain ridges above 2700 feet. Temps varying from the mid-upper 30s to mid-upper 40s. Wind chills in the 20s and 30s ( coldest at highest elevations ).
Tuesday Afternoon
Mostly cloudy. Chance of rain showers. Windy. S-SW winds 10 to 25 mph with higher gusts. Temperatures varying from the upper 40s to lower 50s in upper elevations to the upper 50s to lower-middle 60s ( warmest in downslope locations of northern Wise and Dickenson-Buchanan counties ).
Tuesday Night Into Wednesday Morning
Mostly cloudy. Rain showers becoming likely. Windy. SSW-SW winds 10-25 mph, with higher gusts, on mountain ridges and plateaus below 2700 feet. SW-WSW winds 20-30 mph with higher gusts on mountain ridges above 2700 feet. Temperatures in the 40s to lower 50s.
Wednesday Morning Through The Afternoon
Showers with a chance of thunderstorms. Downpours possible. SW winds 5-15 mph with higher gusts. Temps widespread in the 50s to lower 60s.
A colder than average pattern is being monitored for the first week of April, with the potential for more significant precipitation as winter-spring air masses continue to clash.
Weather Discussion ( Lion In & Out )
Monday Night Update
A flow pattern conducive to significant rainfall amounts is being highlighted during mid-late week. The good news is that the system will be progressive, the bad news being this type of flow is climatologically favored to generate rainfall amounts which are moderate-heavy over very wet ground.
Creeks are running strong and some snow is yet to melt at highest elevations, but mostly the February-March period has been very wet with locally more than 20.00″ of total precipitation.
NAM Model 925 MB Streamline-RH Forecast At 8 AM Wednesday – March 28, 2018
The forecast low-level streamline pattern fits annual climatology = inflow into the Cumberland Mountains from the Gulf of Mexico with orographically enhanced rainfall amounts on rising air flow trajectories. Here is where the pattern is forecast, not any given model prediction of rain amounts. Past climatology, a powerful tool, of similar type settings signals that significant rainfall amounts will be possible to likely from Wednesday through Thursday.
NAM Model 500 MB Vorticity Field Forecast At 11 AM Thursday – March 29, 2018
Upper air dynamics add to low-level orographics by Thursday to continue and enhance the threat for heavy rain with showers and moisture lifting northeast from storms to the southwest ( the local setting does not look favorable for strong-severe thunderstorms which is also good ). If it were not for so much antecedent precipitation during the past 8 weeks this system would not be as much of a concern.
*Although FFG ( Flash Flood Guidance ) is a useful tool, it must be recognized that input precipitation values are typically under-estimated for orographic locations; therefore, high water issues often arise quicker during such wet antecedent conditions than FFG values indicate. The terrain is three-dimensional, complex and is not fully resolved by models, which is where the human factor must come in to improve these model short-comings.
NAM Model 250 MB Jet Stream Forecast At 11 AM Thursday – March 29, 2018
This is not a prolonged flood threat, with the system now expected to clear the area Friday into Saturday, but is one that should not be taken for granted with orographics to be given their proper respect.
Black Mountain Mesonet At 1:40 AM Tuesday – March 27, 2018
Meanwhile, winds are already ROARING at elevations around and above 2800 feet, so caution is advised tonight through Wednesday as tree or tree limb damage may occur due to recent wetness and winter storms.
Flatwoods Mountain Mesonet At 1:55 AM Tuesday – March 27, 2018
Previous Discussion
Although weather conditions may improve by the final hours of March 2018, a setting favorable for more heavy precipitation could push monthly totals into ( or very close to ) double digits for the second consecutive month at the upper elevations in the High Knob Massif.
March 2018 precipitation totals of 6.00″ to 7.00″ have been observed at upper elevations in the High Knob high country in wake of this latest winter storm event that left significant ice accumulations and snow ( 3-5″ of new snow above 3000 feet ).
Wake of Ice Storm At 8:46 AM on Eagle Knob of High Knob Massif ( March 25 )
Snow depths decreased substantially in the high country into the morning hours of Sunday with freezing rain-rain, dropping from max depths ( including old snow ) that reached 3″ to 12″++ prior to the precipitation type change on Saturday afternoon.
Deepest depths of new snow occurred in the early afternoon of Saturday ( March 24 ) when a transition to rain & freezing rain occurred. A general 3″ to 5″ was widespread along and north of the High Knob Massif and Tennessee Valley Divide, with locally less ( to none ) where E-SE air flow downsloped off the high country into the Powell Valley-Big Stone Gap corridor of Wise County.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Snow was so heavy that sticking began in Clintwood with air temperatures above freezing, as snow fell faster than it could melt ( with large flakes ). Roadways became covered at elevations below 1500 feet to the north of the Tennessee Valley Divide versus rain at similar elevations to the south.
GOES-16 Visible Image At 9:22 AM on March 25, 2018
Sunday morning GOES-16 imagery showed both the narrow nature of the system snow band, as well as a striking local contrast between sunshine atop the High Knob Massif and a deck of low clouds banked up along and north of the massif.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The focus now shifts to a pattern favorable for heavy to excessive rainfall, especially in locations along and west of the Cumberland-Allegheny Front and Cumberland Plateau during the March 29-31 period with a tropical fetch of deep moisture from the Pacific Ocean and Gulf of Mexico ( along and in advance of a strong cold front ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 2-6
A return to a colder flow may arise by this weekend and the first week of April, following significant rains and possible thunderstorms.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 6-10
Since this is an evolving and changing pattern, stay tuned for updates as models better resolve the potential wetness of the atmospheric river of moist air expected to impact the region from the Appalachians to Mississippi River Valley.
GOES-16 Mid-level Water Vapor Image At 2:30 AM on March 26, 2018
Observe the long flow field across the Pacific Ocean into the United States, which is already beginning to be joined by a 850 MB flow from the Gulf of Mexico along the Mississippi River Valley.
ALERT Continues For Icing With Freezing Rain At High Elevations In The High Knob Massif – Mixed With Snow – With An Ice Storm In Progress
Note: High traffic volume is making the website slow today, so be patient.
Significant Ice Storm In Progress – Eagle Knob of High Knob Massif – 7:40 PM March 24
*A notable increase in ice accumulation is occurring.
An all out ice storm is in progress in the high country with the potential that the freezing level will drop as 925-875 MB winds back more E-ENE during the evening to also impact communities near and above the level of Flat Gap.
Trees & power lines have started to droop under increasing weight of ice forming at upper elevations in the High Knob Massif, with worst icing above 3300 feet ( note ice & icicles on chain link fence on Eagle Knob ). Snow continues to be mixed during periods of heavier precip ( bright banding on Doppler often indicates this ).
Travel along State Route 619 and Routes 237, 238 and others at the upper elevations is discouraged. Travel along Route 237 has been nearly impossible and restricted to high profile 4×4 vehicles.
At middle to lower elevations along and north of the High Knob Massif temperatures are marginal in colder locations, with 32.7 degrees officially in Clintwood as of 8:00 PM.
ALERT For Areas Of Very Dense FOG Through Saturday Evening Into Early Hours Of Sunday ( March 25 )
High Knob Massif Webcam – University Of Virginia’s College At Wise
Although clouds ( dense fog ) have been widespread at upper elevations throughout Saturday, an increasing concern through Saturday Night will be reduced visibility within areas of very dense fog at middle-lower elevations. Locations with snow cover will have some of the worst fog.
ALERT For A Slower Than Expected Change From Snow To Rain In Wise & Dickenson Counites – Power Outage Potential Increasing
As of early Saturday PM a general 3″ to 5″ of wet snow had accumulated across much of Wise and Dickenson counties, with a slower than expected change. Despite temperatures within the lower 30s snowfall has been heavy enough to accumulate. Mixed sleet has also occurred. Should this continue it will greatly increase risk of power outages.
*Due to sinking air off the High Knob high country on SE flow the amount of snow drastically decreases to the southwest toward Powell Valley and Big Stone Gap.
The atmosphere has become nearly isothermal through a deep layer. It is hoped that afternoon rises will help deter this increasing threat and that these counties will not have to be added into the region facing a crippling fall of snow.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The Heaviest Precipitation Is Yet To Come Into Late Saturday and Saturday Evening and the form it takes will determine how critical this situation becomes. A change to rain is still being predicted by models even though it has been very slow to occur.
ALERT For The Potential Of A Crippling Fall Of Wet Snow Across Eastern Portions Of Southwest Virginia Within A Corridor Between Marion And Martinsville, Centered Upon The Greenbrier And New River Basins
Travel into eastern portions of southwestern Virginia is expected to become hazardous during Saturday, with the potential for a crippling fall of wet snow. Travelers who plan on attending the NASCAR races in Martinsville should be aware that travel along I-81 and Route 58 could become impossible during the climax of this event.
Overnight Into Friday Morning
Partly-mostly clear. Cold. WNW-NW winds 5-15 mph with some higher gusts along middle-upper elevation mountain ridges. Temperatures dropping into the 20s, with 10s to low 20s in coldest upper elevations sites. Wind chill factors in the 10s & 20s, except single digits along highest mountain ridges at upper elevations.
Friday Afternoon
Mostly sunny, with increasing high clouds by mid-late afternoon. Seasonally cold. NW winds 5-15 mph, with higher gusts. Temperatures varying from 30s at upper elevations to the mid 40s to lower 50s.
Friday Night Into Saturday Morning
Increasing clouds. Snow developing during the predawn hours, possibly beginning as a mix or rain, especially to the southwest and south of the High Knob Massif. Variable winds generally less than 10 mph. Temperatures falling into the upper 20s to lower 30s.
Saturday Morning Through The Afternoon
Morning snow or mixed precipitation giving way to rain. Rain may be heavy at times. Cold & nasty. Freezing rain with significant icing possible in the High Knob Massif. Winds SE-SSE at 5-15 mph, with higher gusts, at elevations below 2700 feet. SSE-SSW winds 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures hovering into the 30s to around 40 degrees ( 30-33 degrees in the High Knob Massif ). Areas of dense fog, widespread at the upper elevations.
Saturday Night Into Sunday Morning
Evening rain giving way to overnight showers-drizzle. Freezing rain at upper elevations in the High Knob Massif with a chance of freezing rain at colder mid-low elevation sites. SE-SSE winds shifting ESE-ENE at 5-15 mph with higher gusts. Temps in the 30s. Areas of dense fog.
A setting favorable for heavy to excessive precipitation continues to be monitored for next week. Please stay tuned for later updates on a stormy pattern to close March 2018.
Weather Discussion ( Nasty Pattern )
Saturday Afternoon Update
What is arguably the most sloppy ( NASTY ) system of the entire 2017-18 Winter Season has produced essentially all precipitation types across the mountain area today, with a significant amount of snow and icing.
GOES-16 Mid-level Water Vapor Image At 6:30 PM on March 24, 2018
850 MB Streamlines Showing Air Mass Clash ( March 24 )
A clash between air masses with mT ( maritime-tropical ) and cP ( continental polar ) characteristics is creating havoc across the region today as seen on current GOES-16 images.
A looming and potentially MAJOR weather maker is also already clearly visible on this image, a large river of atmospheric moisture streaming across the Pacific Ocean into the western-southern USA. This will set the stage for what could be a heavy to excessive precipitation event next week.
250 MB Jet Stream Flow Across Pacific Into USA
Given significant snow depths-water content at upper elevations now, and observed water flow during Friday, this needs to melt and flush out of drainage basins of the Clinch, Powell, and adjacent Cumberland before any such system develops.
Late Friday Evening Update
Snow Drifts Along High Crest Lines In High Knob Massif – Friday PM of March 23
Portions of Route 237 ( between High Knob and Big Cherry Lake ) continued to be covered by snow-ice late on Friday, March 23, with large snow drifts remaining along high crest lines.
A significant weather event is expected to develop across southwestern Virginia during Saturday, with a nasty array of weather conditions.
While temperatures aloft will dictate major precipitation types, low-level temperatures will also be locally critical.
Black Mountain Mesonet At 12:05 AM on March 24, 2018
Adiabatic upslope cooling into the high country along the Wise-Scott-Lee County border may require an ICE Storm Warning ( the Wise-Harlan County border may also be impacted, but with less severe conditions ).
Following morning snow or mixed precipitation most of the area is currently expected to change over to a cold rain, but temperatures will remain unseasonably cold and it could be a close call for many locations. Stay tuned for updates that may be needed as this system develops.
Previous Discussion
Sunshine during a TGIF should be savored as a truly nasty setting develops into this weekend as another significant precipitation event unfolds.
High Knob Massif Webcam – University Of Virginia’s College At Wise
March 22 began with stacked lenticular clouds above the rime capped crest zone of the High Knob Massif.
Snowfall Totals & Ground Depths ( As of Morning of March 22 )
City of Norton Water Plant: 3.0″ 2″ ground depth ( 1.28″ event total )
High Chaparral: 3.5″ ( 2-3″ ground depth )
High Knob-Eagle Knob: 7.0″ ( Variable depths with 1-2+ feet drifts )
This event continued to accentuate the wetness of 2018 with more than 2.00″ of total water equivalent precipitation falling during the March 16-22 period at Big Cherry Lake Dam ( 4.86″+ in March and 24.71″+ since January 1 ).
Snowfall and snow depths generally came in on the lower end of my forecast spread with this most recent event. The exception being at upper elevations in the High Knob Massif between Bowman Mountain and the Thunderstruck Knob of Powell Mountain, where up to 7″ or more of snow fell.
GOES-16 Visible Image At 10:17 AM on March 22, 2018
Although a mixture of clouds and snow were present, there was no mistaking the outline of the High Knob Massif as it stood above the horizon of far southwestern Virginia on morning GOES-16 satellite imagery ( above ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
A thin layer of orographic clouds were forming along the summit of the massif at the time of the GOES-16 image, as viewed from the UVA-Wise Webcam above, and with motion were observed to be part of standing waves through which the air passed as it flowed southeastward toward the TRI.
NAM 12 KM Model Total Precipitation Forecast – Next 84 Hours
The main focus now shifts to the next system which will be a wet one, with generally good model agreement on a well defined corridor of moisture; although, total amounts of precipitation remained varied.
GFS Model Total Precipitation Forecast – Next 84 Hours
Thursday evening ( 00 UTC ) runs of both the NAM and GFS models shifted more toward the ensembles of the GFS and European Model with respect to placement of the main axis of this precipitation corridor.
NAM 3 KM Model Total Snowfall Forecast – Next 60 Hours
Models remain in considerable disagreement as to how much cold air deep enough to support snow will remain in place; therefore, they diverge on potential amounts.
GFS Model Total Snowfall Forecast – Next 60 Hours
The axis of the snowband is similar on both models during this run, but amounts for locations outside the axis varies.
At the Wise gridpoint, for example, model forecast snow amounts range from 1″ on the high-resolution NAM 3 KM Model to 5″ on the GFS Model ( the 12z run of the European Model was a compromise with 3″ predicted ).
If the precipitation band shifts southwest or northeast these amounts will change, and potentially in a big way.
Past climatology with warm fronts suggests that the area to the north and east of the Cumberland Mountains, focused upon the New River and Greenbrier valleys, will be most favored for a significant amount of wet snow. That is the model consensus.
If movement of the actual low center ( the storm track ) shifts more south, then that would keep this area within snowfall for a longer period of time versus if the the storm track shifts north. There remains some wiggle room.
ALERT For A Significant Winter Storm Event For Late Tuesday Night Through Wednesday Night – Especially At Middle To Upper Elevations
Deep moisture associated with a developing upper level low will redevelop precipitation through Tuesday evening with a transition to snow from top to bottom beginning during the 8-11 PM time period Tuesday. Snow levels will drop in elevation to Norton-Wise during the overnight and reach valley floors below 2000 feet, along and north of the High Knob Massif-Tennessee Valley Divide, by Wednesday AM.
A deformation snowband and comma-head swirl will keep snow over the area through Wednesday evening into early hours of Thursday, with a possible mix during the day at lower elevations below 1500-2000 feet.
Total Snowfall Forecast Tuesday Night-Thursday AM
*Lower Elevations – Below 2000 Feet 1″ to 3″
Middle Elevations – 2000 to 3000 Feet 2″ to 6″
Upper Elevations – Above 3000 Feet 4″ to 8″ with locally higher amounts – especially within the High Knob Massif and along the much more narrow crest lines of Black Mountain
Many valleys within the High Knob high country are higher than Pine Mountain, such as within the High Knob Lake and Big Cherry Lake basins where valley floors are higher than the highest peak on Pine Mountain in Dickenson County ( 3149 feet at Birch Knob of Pine Mountain ). Therefore, I mainly group Pine Mountain in with the Middle Elevation Zone given only a few small peaks rising above 3000 feet along its 120 air mile extent.
The Pine Mountain crest actually becomes lower than the Wise Courthouse southwest of Harlan County in southeastern Kentucky. Pound Gap of Pine Mountain, at 2372 feet, is about the same as the City of Norton Water Plant and is also lower in elevation than the Wise Courthouse ( 2454 feet ).
Target Snowfall 4.0″ in Norton-Wise ( +/- ) 2″ error potential. This implies potential for 2″ to 6″ of snowfall during the period. MAX snow depths on the ground will likely be near to LESS than total snowfall amounts in most locations.
*Snow accumulations of 1″ or less are generally expected at elevations below 1500 feet, except within upslope locations along and north of the High Knob Massif and Tennessee Valley Divide where air will be rising and cooling.
While Power Outages will be a MAJOR Threat in central and northern Virginia into West Virginia, the local risk will be more limited but not non-existent. Lower density snow at upper elevations, in colder air, will help to lower the risk where heaviest snow falls above 3000 feet. The middle elevation zone, between 2000 and 3000 feet, will possess the highest local risk of power outages. Ultimately, this will be determined by how much snow accumulates.
Reference my Mesoscale Discussion below and stay tuned for updates which may need to be issued once the banding features develop. Deep moisture will generate widespread snow ( not a snow shower type of setting ) and areas that generate low-level convergence will help form mesoscale bands of heavy snow embedded within the larger snowfall field. That is the proper way to approach a system like this.
*A snow shower-flurry setting develops only toward the end of this system as the vertical moisture profile becomes less and the snowfall producing moisture become relegated to lowest levels. So this should be forecast as snow, with locally heavy bands.
Although beneath a developing upper-level low, temperatures aloft over the mountains will be 20-30 degrees Fahrenheit higher than last week’s intense snow squall setting. So this will not be a setting favorable for snow bursts, instead any heavy snow of that nature will more likely be associated with a mesoscale band outside of orographic lifting zones.
Overnight Into Monday Morning
Increasing clouds. Winds SSW-SW at 5-15 mph with higher gusts along mid to upper elevation mountain ridges. Temps varying from 30s in mountain valleys to the 40s on exposed ridges and plateaus.
Monday Afternoon
Mostly cloudy. A chance of showers, thunder possible, toward sunset. Winds becoming SE to SSE at 5-15 mph with higher gusts. Temperatures varying from low-mid 50s at upper elevations to the 60s ( warmest downslope sites of northern Wise and Dickenson-Buchanan counties with upper 60s to around 70 degrees. ).
Monday Night Into Tuesday Morning
Rain with a chance of thunder. Local downpours. Winds SE to SSE at 5-15 mph, with higher gusts, below 2700 feet. SSE to SSW winds 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures in the 40s to around 50 degrees. Areas of fog, widespread and dense at upper elevations in upslope locations of the High Knob Massif.
Tuesday Afternoon
Rain with a chance of thunder. Local downpours. SSE winds at 5-15 mph, with higher gusts, shifting to SW by late. SSE-SW winds 10 to 20 mph, with higher gusts, along mountain ridges above 2700 feet. Areas of fog, dense and widespread at upper elevations ( orographic cap clouds ). Temps in the 40s upper elevations and in the 50s at low-mid elevations, dropping by late afternoon.
Tuesday Night Into Wednesday Morning
Rain changing to snow from top to bottom. Snow may be heavy at times. Winds SW-W at 10 to 20 mph with higher gusts. Temps falling into the 20s to lower 30s ( around 20 degrees on highest peaks ). Low cloud bases with rime formation at upper elevations. Wind chills dropping into 10s and 20s, except single digits at highest elevations.
Wednesday Morning Through The Afternoon
Snow. Snow will be heavy at times. Snow may mix with rain at lower elevations, especially below 1500 feet and to the south and southwest of the High Knob Massif and the Tennessee Valley Divide. WNW-NW winds 10-20 mph with higher gusts. Temperatures varying from 20s in the upper elevations to the mid 30s. Wind chills in the 10s and 20s, except locally colder in gusts at highest elevations. Rime formation at highest elevations.
Wednesday Evening Into Thursday Morning
Snow. Snow may be heavy at times during the evening before tapering off to snow showers and flurries into the overnight. Winds WNW-NNW at 5-15 mph, with higher gusts. Temperatures varying from the upper 10s to the upper 20s ( coldest at highest elevations ). Wind chills in the 10s & 20s, except 0 to 10 degrees highest elevations.
A very stormy pattern is looking to dominate the next 1-2 weeks, with potential for heavy to excessive precipitation currently being monitored into next week.
A complex system will be developing right over top of the mountain area in mid-upper upper levels in coming hours, with an influx of colder air aloft helping to change rain into snow from top to bottom over time ( changing first at the summit levels of the High Knob Massif & Black Mountain ).
NAM Model 500 MB Analysis At 2 PM Tuesday – March 20, 2018
Being beneath an upper level low can always offer several complications, and this setting will likely be no different as pieces of energy swirl around the low to help develop areas of enhanced ( mesoscale ) snowfall.
NAM Model 500 MB Forecast At 8 AM Wednesday – March 21, 2018
Models are initially wanting to develop the heaviest snow along a low-level convergence field where westerly and easterly air flow trajectories will be coming together.
NAM Model 850 MB RH-Wind Streamline Forecast at 8 PM Tuesday – March 20
Convergence initially in the High Knob Massif area shifts to the northeast and east. Note easterly 850 MB streamlines to the northeast into southern West Virginia and central parts of Virginia ( below ) at 11:00 PM Tuesday evening. Easterly flow across central-northern Virginia is coming off the western Atlantic Ocean to advect or transport the best moisture for heaviest snowfall development.
NAM Model 850 MB RH-Streamline Forecast at 11 PM Tuesday – March 20
By Wednesday morning ( below ) the convergence line is still forecast to be across central Virginia & West Virginia, and the heaviest snow should occur from that area north-northeast into Pennsylvania. Other areas with moderate to heavy snow, of lesser extent, will be along the windward slopes of the Cumberland Mountains & Blue Ridge in the southern Appalachians ( where air possessing a westerly component will be lifted ).
NAM Model 850 MB RH-Streamline Forecast at 8 AM Wednesday – March 21
The setting for heavier snow actually improves locally during Wednesday afternoon into Wednesday evening as the deformation band shifts southeast and the low-level flow becomes more WNW-NNW ( NW ) and orographic forcing increases into the Cumberland Mountains.
NAM Model 850 MB RH-Streamline Forecast at 5 PM Wednesday – March 21
Deep moisture + significant orographic forcing will produce moderate to heavy snowfall, with worst conditions likely to develop in this area during late Wednesday afternoon into the evening hours ( especially around and after sunset ).
NAM Model 850 MB Temperature Forecast at 11 AM Wednesday – March 21
The coldest air will be developing along the western side of the 850-700 MB lows, which will help lower snow density at upper elevations ( this will also add some fluff factor such that this could help increase snow amounts and is a wild card factor in this system ).
Previous Discussion
Following the first strong to locally severe thunderstorms of Meteorological Spring the pattern will be transitioning back into a wintry mode in coming days as part of what is looking like an increasingly stormy early spring regime.
JKL Doppler – Courtesy of Jackson, Ky., NWS Forecast Office
Although thunderstorms will become possible later Monday into Tuesday, the severe risk is currently forecast to remain southwest of the mountain area as another Miller Type B cyclone develops across the region.
Central-southern Tennessee will be under the gun for a possible outbreak of severe thunderstorms. This will need to be closely watched into Tuesday.
Storm Prediction Center Risk Regions To 8 AM Tuesday – March 20, 2018
Colder air will begin to flood into the area Tuesday night into Wednesday morning, with a change to snow from the highest elevations downward over time. Trajectories of air flow will be important to initial accumulations before a change into NW flow occurs, so stay tuned for updates.
The Storm Prediction Center Has Issued A Marginal Risk For Possible Severe Thunderstorm Development On Saturday ( March 17 )
Storm Prediction Center Risk Regions For Saturday – March 17, 2018
Former Alerts
ALERT For Strong SW-W Winds Developing Tonight At Upper Elevations…Then Mixing Downward Across The Area During Thursday
Strong upper elevation SW-W winds will develop tonight, with blowing-drifting snow possible in open areas & along high crest lines. This could increase travel problems along State Route 619, State Route 706, Routes 238, 237, and State Route 160, to note a few, impacted by 6″ to 12″ of snowfall.
Strong SW-W winds will mix downward to middle elevation mountain ridges & exposed plateaus at some point between tonight and Thursday morning, then downward into lower terrain ( below 2000 feet ) during the day Thursday.
Wednesday Night Into Thursday Morning
Partly cloudy evening skies will give way to mostly cloudy conditions. Becoming windy. Blowing-drifting snow at the high elevations. SW-W winds increasing to 10-20 mph, with higher gusts, on mountain ridges-exposed plateaus below 2700 feet. WSW to W winds increasing to 20-30 mph, with higher gusts, on mountain ridges above 2700 feet. Temps dropping into the 10s and 20s, then rising through the 20s at upper elevations overnight into morning ( nearly steady or rising above 30 degrees on exposed middle elevation mountain ridges & plateaus ). Wind chills rising from the single digits below & above 0 degrees at highest elevations into the 10s toward morning. Wind chills in the 10s and 20s along middle elevation ridges-exposed plateaus.
Thursday Afternoon
Partly to mostly cloudy ( mid-level clouds ). Windy. SW-W winds 10-25 mph, with higher gusts. Temperatures varying from 30s to low 40s at upper elevations to the upper 40s to lower 50s ( milder in downslope locations with no snow ).
Thursday Night Into Friday Morning
Mostly cloudy. Small chance of rain showers or a mix of snow showers possible at mid-upper elevations. Winds shifting WNW-NW at 5 to 15 mph, with higher gusts. Temps varying from 20s at upper elevations to the low-middle 30s ( milder in downslope locations, especially to the south and southwest of High Knob Massif-Tennessee Valley Divide ).
Friday Afternoon
Mostly sunny. Some increase in high clouds. Light NW-N winds, except breezy to gusty along high mountain ridges. Temperatures varying from 30s to lower 40s at highest elevations over lingering snow cover to upper 40s to low 50s ( warmer south to southwest of the High Knob Massif and Tennessee Valley Divide ). Wind chills in the 20s to lower 30s at upper elevations.
The potential for another major winter storm is being monitored for next week. Stay tuned for later details.
Reference the above link for a review of one of the greatest winter storms ever documented in this region ( scroll down to the section about the then 20th Anniversary of this Monster Storm ).
Recap Of Snow Squalls ( March 13-14 )
Reference my 031118 Forecast for information on the complete storm event including forecast details.
To understand how this was an easy forecast to predict days in advance, consider the following:
The temperature in downtown Norton is 60 to 70 degrees, while at the same time the temperature in downtown Wise is 0 degrees. What would you think about that?
Now, invert that temperature difference into the vertical and you have the setting which developed late on March 13 into morning hours of March 14.
When orographic lift is applied, it becomes chaos with widespread significant snowfall. No places missed out in the upslope zone, even though amounts varied.
In downslope locations, such an extreme vertical temp profile acted to overcome the typical inverse forcing with orographics ( often called downsloping ) and generated localized streaks of heavy snow. Some to numerous places missed out.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The most intense snow squalls of the 2017-18 winter season created widespread, significant accumulations across the mountain area with Winter Storm Warning criteria easily exceeded within upslope locations of Wise County.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Snow squalls & local snowstreaks ( training squalls ) created whiteout conditions into morning hours of March 14, with new snowfall accumulations ( since sunset March 13 ) in the upslope zone varying from 2-3″ on the low end of the stick to 10″+ at upper elevations in the High Knob high country.
As little as 1″, by contrast, was reported in downslope sites such as in the Town of Big Stone Gap ( 1.4″ reported at the official recording site in the Tri-Cities ).
Snowfall & Snow Depth Reports ( March 13-14, 2018 )
Big Stone Gap 1.0″ ground depth
( Paxton Allgyer )
Clintwood 1 W NWS: 2.7″ 2-3″ ground
( Wayne Browning )
*City of Norton WP 6″-7″ ground depth
( Andrew Greear & Joe Carter )
*Parsons Gap – Wise 6.5″ ground depth
( Wally Smith )
*Depth included some old snow.
New Snow Depth At 9:52 AM – High Chaparral of High Knob Massif
Joe & Darlene Fields measured a total of 10.0″ of new snow in the High Chaparral community of the High Knob Massif, with 8″ accumulating between 7 PM March 13 and 9:52 AM March 14, followed by an additional 2″ by the conclusion of this portion of the event ( 12.5″ total during March 12-14 ).
High Chaparral of High Knob Massif At 9:53 AM on March 14, 2018
High Chaparral Community 10″ of total snow depth March 12-14: 12.5″ Total
( Joe & Darlene Fields )
GOES-16 Visible With Snowstreaks
Snowstreaks developed into March 14 to produce prolonged periods of whiteout conditions along trajectories in which they formed.
Although several people reported hearing thunder, amid or immediately prior to onset of very heavy snow, including myself, the closest lightning strikes detected were very near the Virginia-Kentucky border in Pike County, Ky.; however, that does not mean that they did not occur on this side of the state line.
Closest Lightning Strike Detected Over SE Pike County Prior To Local Thundersnow
While the lightning detection system is very good and likely picks up most strikes, a few likely escape in such settings with CSI and a slantwise cloud over mountainous terrain. There is no doubt that local snow was convective, with wind and intense snow so heavy that visibility was reduced to 100 meters or less amid climaxes.
Focus now shifts to an increasing pressure gradient as a frontal boundary approaches and stalls over the area, with wobbles back and forth to determine local temps as a rather significant NW-NE to SE-SW gradient develops across the boundary into this weekend.
