The Storm Prediction Center Has Issued A Marginal To Slight Risk Of Severe Thunderstorm Development For Friday Afternoon & Friday Night In Locations Along And West-Southwest Of The Virginia-Kentucky Border
While places west to north of the Cumberland Mountains will be at greatest risk, locations along the mountains will need to closely monitor thunderstorm development later Friday & Friday night.
A FLASH FLOOD WATCH IS IN EFFECT THROUGH SUNDAY AFTERNOON FOR ALL COUNTIES ALONG THE VIRGINIA-KENTUCKY BORDER. GIVEN RAIN ALREADY OBSERVED AND THE UPPER AIR-SURFACE SETTING THIS IS A PARTICULARLY DANGEROUS SITUATION.
ALERT FOR HIGH WATER LEVELS ALONG CREEKS & RIVERS AND THE THREAT FOR FLASH FLOODING AND RIVER FLOODING WITH ADDITIONAL HEAVY RAINS.
*A general 3.50″ to 4.00″ of rain has fallen across upper elevations in the High Knob Massif since 2:00 AM on April 20. Roaring water levels and dangerously slick banks are being observed now ( as of 3:00 PM April 22 ). Additional rainfall will threaten low-lying sites downstream along the Wise-Scott-Lee border through Sunday with flooding and flash flooding. Remain alert to changing conditions. Extreme caution is advised.
Communities at risk for flash flooding and flooding include but are not limited to the following: City of Norton, Ramsey, Tacoma, Coeburn, Dungannon, Fort Blackmore, Ka, Appalachia, Big Stone Gap, East Stone Gap and Cracker Neck, Jasper, Peterson, Duffield, Pennington Gap as well as communities along and upstream of tributaries of the Clinch and Powell rivers.
**In addition, flash flooding and river flooding will need to be closely watched for communities across northern Wise and Dickenson counties where creeks are also running high on tributaries of the Russell Fork and Levisa Fork rivers.
*Do NOT Cross Flooded Roadways. TURN AROUND AND DO NOT DROWN – A LIFE CAN NOT BE REPLACED!!!
Remainder of Saturday Afternoon Into Sunday AM
Periods of showers and thunderstorms. Rain will be heavy at times, especially by the predawn-morning hours. Remain alert for flash flooding-flooding. NE-E winds increasing to 5-15 mph, with higher gusts. Temperatures near steady or falling into the 40s. Widespread fog above 2500-3000 feet, with areas of dense fog at lower elevations.
Sunday Morning Through Sunday Afternoon
Rain, with a chance of thunderstorms. Rain will be heavy at times. Remain alert for continued rises on creeks-rivers. E winds 5-15 mph, with higher gusts, below 2700 feet. Winds E-ESE at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Unseasonably chilly with temperatures varying from upper 30s to lower 40s at highest elevations to the mid-upper 40s to near 50 degrees. Widespread dense fog at upper elevations. Wind chills in the 20s and 30s at upper elevations.
Sunday Night Into Monday Morning
Rain tapering to showers and drizzle. Low clouds with areas of dense fog ( especially at higher elevations ). Winds NE-E at 5-15 mph, with higher gusts. Temperatures varying from 30s at highest elevations to the 40s. Wind chills in the 20s and 30s in upper elevations ( above 3000 feet elevation ).
Weather Discussion ( Flood Threat )
Saturated ground from recent days of rainfall and another storm system is threatening the mountain area with flash flooding and flooding.
The current break in rainfall will be short-lived with a threat of training rains moving back into the area by late afternoon into tonight.
In addition, a notable dip in the jet stream will provide upper air divergence aloft to support rising air through a deep layer of the atmosphere by the predawn-morning hours of Sunday to enhance the heavy rainfall potential.
*Isentropic lifting, not “over-running,” of very moist air over cooler air near the surface will aid rainfall along with orographic lifting in low-levels by major terrain features. This all occurs below significant 500-250 MB upper air divergence ( diffluence ) with the cutting-off of a upper-level low and cold pocket aloft.
The period that looks especially worrisome is during the daylight hours of Sunday, according to the latest model runs Saturday night. Several more inches of rain will be possible across the southern Appalachians ( the eastern slopes received much less rain into Saturday so they can handle more rainfall than western slopes…but all these areas from the Cumberlands to the Blue Ridge will have enhanced risk of flooding into Sunday night ).
Up to this point ( Saturday PM ) rainfall amounts have been under-estimated by models in many places; therefore, with several more inches being forecast the flood threat in this setting is “higher than average.”
Although any one living or driving through flood prone, low-lying areas will need to remain alert, a threat for flash flooding-river flooding means that everyone should pay close attention to changing conditions through tonight and Sunday.
Stay tuned to NOAA Weather Radio and your favorite media sources for possible WARNINGS that may be needed during this event.
Mostly clear ( some high clouds ). Large vertical temp difference between colder valleys and milder mountain ridges. Light winds. Temps varying from 30s in colder mountain valleys to the 50s along exposed ridges. Frost possible within the coldest valleys.
Good Friday Afternoon
Partly sunny & unseasonably warm. Small chance of an isolated shower or thunderstorm. Light SW to W winds. Temperatures varying from 60s to lower 70s at highest elevations to the lower-middle 80s.
Friday Night Into Saturday Morning
Partly to mostly cloudy ( mid-high clouds ). Milder. SSW-WSW winds 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges. Light winds in valleys. Temps varying from 40s in mountain valleys to the 50s to around 60 degrees on exposed mountain ridges-plateaus.
Partly to mostly cloudy. A chance of hit-miss showers and thunderstorms. SSW to SW winds 5 to 15 mph, with higher gusts. Temperatures varying from 60s in upper elevations to the mid-upper 70s.
Saturday Night Into Easter Sunday Morning
Partly-mostly cloudy. Mild. Winds SSW-SW at 5-15 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. Winds SW 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures generally from the upper 40s to the upper 50s.
Easter Sunday Afternoon
A chance of showers and thunderstorms. SW winds 5-15 mph, with higher gusts. Temperatures widespread in the 60s to lower 70s.
Weather Discussion ( Wetter Pattern )
Spring-time in the mountains is currently featuring large temperature spreads in both the vertical ( between valleys and ridges ) and diurnally ( between night and day ).
Although colder mountain valleys dropped to frosty levels during Thursday morning ( around or below freezing in the coldest valleys at upper elevations ), and will again fall into 30s on Friday morning, this is a warm pattern that looks to continue through coming days.
Increasing low-level moisture will help to narrow temperature spreads ( both between valleys-ridges and between night and day ) and increase chances for showers and thunderstorms this weekend into much of next week.
Chances for hit-miss showers or local thunderstorms will begin to increase by Saturday afternoon ( only a very small chance of something isolated popping Friday afternoon ).
A wetter pattern is being advertised by the medium range models through the second half of April, which at this time of year typically implies rounds of showers-thunderstorms with the emphasis being on rounds.
There will be many dry hours in between upper air disturbances that trigger this activity. Only if a front stalls over the mountain area will activity have the opportunity to become prolonged. That will be an element to watch ( the positioning of fronts ) through the next couple of weeks as upper air trough formation into New England may offer the chance for an enhanced southwest-northeast temperature gradient to form across the eastern USA ( generating a stormy zone over or close to the Mountain Empire ).
High clouds. Large vertical temperature spread between milder mountain ridges and colder valleys. S to SW winds 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges ( increasing to 10-20 mph along highest mountain ridges toward morning ). Temperatures varying from low-mid 40s in cooler mountain valleys to the middle 50s to lower 60s.
Partly cloudy. Unseasonably warm. Chance of hit-miss showers and thunderstorms. Winds SW 5-15 mph, with higher gusts. Temperatures varying from 60s in upper elevations to the middle-upper 70s.
Tuesday Night Into Wednesday Morning
Hit-Miss showers & thunderstorms. Local downpours, especially during the evening. Winds shifting WNW-NW at 5-15 mph, with higher gusts. Temperatures dropping into the 40s to lower 50s overnight into morning.
Sunny. Blue skies. Pleasant. Winds N-NE at 5-10 mph, with higher gusts. Temperatures varying from upper 50s to low 60s at highest elevations to the upper 60s to lower 70s.
Wednesday Night Into Thursday Morning
Mostly clear. Some high clouds. Light valley winds. Winds shifting E-SSE at 5-10 mph, with higher gusts, along middle to upper elevation mountain ridges. Large vertical temp spread between colder valleys and milder ridges. Temps varying from 20s to lower 30s in coldest valleys to the 40s along exposed mountain ridges.
Weather Discussion ( Radical )
A radical change in weather conditions have occurred during recent days, from heavy snow and drifting with bitter winds at highest elevations to the first 80+ degree warmth of 2017 amid lower elevations ( below 2000 feet ).
Snow capped high mountain summits from the High Knob Massif and Russell Beartown Mountain southwest along the Appalachians to massifs of Mount Rogers-Whitetop, Roan Mountain, and the Black Mountains stood clearly out during afternoon hours of April 7. Snowfall totals of up to 13.0″ were reported on Mount Mitchell, with 8″ near the summit level of Mount LeConte in the Great Smokies.
This was a notable late season winter storm for the top of the Appalachians ( featuring 50-60+ mph wind gusts ).
Drifting snow was also notable, with 1-2 feet at upper elevations in the High Knob Massif ( 17″ shown below by afternoon ) along the highest mountain crest lines ( and high gaps ).
Spring continues to progress, despite this wintry blast, especially within lower-middle elevations which missed accumulating snowfall ( at elevations below 3000 feet ).
A chance for hit-miss showers and thunderstorms, with large variations in rainfall amounts, will be possible by Tuesday afternoon into Tuesday Night.
The exact placement of heavier rain amounts, as noted above, can not be known with the model only generating a best guess. As is typical during the warm season, large variations in rain amounts over short distances are common when convection begins to rule the precipitation pattern.
Although temperatures will be chilly in mountain valleys during Wednesday Night into Thursday Morning, especially high valleys within low dewpoint air and drainage flows, the general pattern is unseasonably warm in the MEAN during the next 1-2 weeks.
While jet stream disturbances will have greatest impacts upon western and northern portions of the USA, trailing fronts will gather enough moisture and instability for periodic chances of showers and thunderstorms. If any front stalls, as some models suggest by late week into next week, this could help to prolong precipitation chances. Daily details yet to be determined.
ALERT For Accumulating Snow Overnight Into Friday Morning At Elevations Above 2000 Feet – Significant Accumulations Are Expected At The Upper Elevations With Lesser Amounts Below 3000 Feet
*Snow Depth Forecast Into Friday – April 7
Below 2000 Feet: Little to no accumulation
2000 to 3000 Feet: Dusting to 2″
Above 3000 Feet: 2″ to 8″+
*The greatest snow amounts will occur at the highest elevations. Forecast error potential ( +/- ) 1″ on the listed elevation ranges to imply 1″ to 3″ possible at 3000 feet elevation.
The level of accumulating snow ( 1-2″ at the summit level of the High Knob Massif as of 8:00 PM Thursday ) will drop downward toward 2000-2500 feet by Friday morning ( on the upslope side of the mountains ). Conditions will begin to improve after 11:00 AM Friday at all elevations ( but will remain windy & cold ).
Rain and snow, or a rain-snow-sleet mixture is expected to occur at elevations below 2500 to 2000 feet, with little to no accumulations below 1500-2000 feet in elevation.
Overnight Into Mid-Morning Friday
Rain changing to wet snow above 2000 feet. Sleet possible. Sticking snow levels dropping toward 2000 to 2500 feet by morning. Rain showers or a mix continuing at elevations below 1500-2000 feet. Snow heavy at times, especially at higher elevations. Windy. Cold. Winds WNW-NW at 15-30 mph, with higher gusts. Temperatures varying from upper 20s to middle 30s to the upper 10s to middle 20s at highest elevations. Wind chill factors varying from 10s to lower 20s to the single digits and 10s ( except near to below zero in stronger gusts at high elevations in the High Knob Massif ). Blowing and drifting snow at the highest elevations.
Partly cloudy. Windy & unseasonably cold. Winds WNW-NW at 10-20 mph, with higher gusts. Temperatures varying from 30s in upper elevations to the 40s. Wind chills in the 20s and 30s, except 10s in gusts at highest elevations.
Friday Night Into Saturday Morning
Mostly clear. Cold. Winds diminishing in deeper valleys. NW winds 5 to 15 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures in the 20s to lower 30s, except 10s within upper elevation valleys that can decouple from boundary layer flow ( i.e., winds calm with drainage flow development ).
Partly sunny ( high clouds possible ). Milder. Light winds shifting W-SW at generally less than 10 mph. Temps from 40s in upper elevations to the mid-upper 50s.
Saturday Night Into Sunday Morning
Mostly clear. Large vertical temperature spread developing between colder valleys and milder ridges. Light southerly winds at less than 10 mph on most mountain ridges. Temps varying from 20s to lower 30s in valleys to 40s on exposed mountain ridges-plateaus ( 10s to lower 20s in colder high valleys of the High Knob Massif ).
Weather Discussion ( Elevation Snow )
As typical for early and late season events, snow has been elevation biased so far and is expected to continue that way into Friday; although, snow levels will be dropping toward 2000 to 2500 feet over time.
Snow began falling around mid-day at the summit level of the High Knob Massif, with enough to coat the grass ( and especially the woods ) by 5:00 PM. A burst of heavier snow later brought amounts into the 1″ to 2″ range by 8:00 PM.
As of 9:30 PM moderate to heavy snow was reported by Darlene Fields in High Chaparral, at 3300 feet, but it was still not sticking to the ground there ( it likely will begin soon ). Therefore, even at elevations above 3000 feet a notable range in snow depths and amounts will occur as colder air does not begin to really pour in until after the Midnight hour ( i.e., overnight hours of Friday ).
Note 0.10″ in the rain gauge at the Black Mountain Mesonet site from 9:50 to 10:15 PM with heavy snow; however, wind gusts of 40-50+ mph means that even with an alter wind shield the rain gauge can not begin to catch nearly all that fell. Determining amounts at high elevations are going to be complicated by very strong winds + above freezing ground temperatures.
Very strong NW winds, with gusts around 50 mph or locally greater at highest elevations, are a real factor at mid-upper elevations and will help enhance rain-snow amounts into the overnight-morning hours of Friday.
Conditions will begin to improve, with respect to snowfall, after the mid-morning to mid-day period Friday behind the 850 MB thermal MIN ( -6 to -7 Celsius centered on 11:00 AM ) which drops air temps into upper 10s to lower 20s atop the High Knob Massif & Beartown peaks in southwest Virginia.
*The problem for those living in middle elevations being that as the air turns colder and snow falls the moisture supply will begin to wane Friday, thus limiting accumulations along the mountain chain southwest of the eastern West Virginia highlands where the moisture connection will persist longer in time.
Cold nights will continue through this weekend, especially amid mountain valleys. By Saturday night a large vertical temperature spread will develop between colder valleys and milder ridges. Vertical temperature differences of 20-30+ degrees will become possible into Sunday morning.
The Storm Prediction Center Has Issued A Slight Risk For Severe Thunderstorm Development Wednesday Afternoon-Evening Into The Overnight ( With An Enhanced-Moderate Risk Toward The Southwest )
Stay tuned to NOAA Weather Radio and your favorite media sources for Watches and Warnings that may be needed later Wednesday into Wednesday night.
The Potential For Accumulating Snowfall Is Also Being Monitored For Thursday Into Friday ( Significant Snow Amounts Will Be Possible, Especially At The Middle To Upper Elevations Above 2500 to 3000 Feet ).
Overnight Into Tuesday Morning
Showers likely. A chance of thunder. SSW to WSW winds increasing to 10-20 mph, with higher gusts ( especially on middle to upper elevation mountain ridges. Temperatures widespread in the upper 40s to mid-upper 50s. Dense fog on high mountain ridges ( widespread in High Knob Massif ).
Partly to mostly sunny. Warm. SW-W winds 5-15 mph, with higher gusts. Temperatures varying from lower-middle 60s in upper elevations to the lower-middle 70s.
Tuesday Night Into Wednesday Morning
Partly to mostly clear. Light winds. Large vertical temp spread between colder valleys and milder ridges. Temps varying from 30s to lower 40s in colder valleys to the lower-middle 50s along exposed ridges.
Partly sunny ( high clouds ). Warm & windy. A chance of hit-miss afternoon showers & thunderstorms ( any storms could become strong to severe ). SSE to S winds 10-20 mph, with higher gusts. Temperatures varying from 50s at highest elevations to the upper 60s to middle 70s.
Wednesday Evening Into Thursday Morning
Showers & thunderstorms. Some storms could be strong to severe. Downpours likely. Widespread dense fog ( capping orographic clouds ) at upper elevations in High Knob Massif. Winds shifting SW & increasing to 10-20 mph, with higher gusts. Turning colder by morning. Evening temperatures widespread in the 50s, then dropping into the 40s and 30s by morning ( coldest at upper elevations ).
Rain showers will change to snow showers at highest elevations in the High Knob Massif during Thursday morning, with snow levels dropping during the day into middle and perhaps lower elevations ( by late ) along the upslope side of the mountains. Accumulations during the day are currently expected to be mainly at the highest elevations, with sticking snow levels then dropping rapidly through middle elevations by mid-late PM into early evening.
Windy & turning cold. Rain showers changing to snow showers. Sticking snow levels dropping toward 2000 to 2500 feet by late. SW winds shifting WNW at 15-25 mph, with higher gusts. Temperatures falling into the 30s at lower-middle elevations, into the 20s at upper elevations, within locations along and north to northwest of the High Knob Massif-Tennessee Valley Divide ( milder to the south ). Wind chills dropping into the 10s and 20s.
Widespread snow, heavy at times, is expected along the upslope side of the mountains ( WNW-NW of the Cumberland-Allegheny Front ) Thursday evening into Friday morning. Significant snow amounts will be possible, especially at mid-upper elevations above 2000-3000+ feet.
Thursday Night Into Friday Morning
Snow & snow showers. Snow heavy at times. Windy. Cold. Winds WNW-NW at 15-25 mph, with higher gusts. Temps varying from upper 20s to lower 30s to the upper 10s to lower 20s at highest elevations ( milder lee of mountains into the Great Valley ). Wind chill factors varying from 10s to lower 20s to the single digits and 10s ( except near to below zero in stronger gusts at highest elevations in the High Knob Massif and other major mountain ranges ).
Cold night-time temperatures will continue through this upcoming weekend, especially in mountain valleys.
Weather Discussion ( Blast Of Winter )
A clash of spring and winter is the main focus for coming days, with strong-severe thunderstorms ( and a possible outbreak of severe storms ) giving way to upslope snow.
Although spring activity has been increasing in the natural world, the Ole Man Of Winter has different ideas amid this 30th Year Anniversary Week of the great April 2-5, 1987 snowstorm that buried the mountain landscape.
The April 2-5, 1987 snowstorm produced snow depths of 20″ to 26″ in Clintwood ( total fall was 33.8″ ). Gary Hampton reported 3 feet of snow depth at the City of Norton Water Plant, at the base of the High Knob Massif, with electrical engineer Carl Henderson, of Blue Ridge Public Television, reporting 2-6 feet ( 4 feet average ) depths on Eagle Knob of the High Knob Massif.
Although snowfall amounts are not expected to be anything like April 1987, it is certainly possible that 6″ to 12″ of snow could fall in upper elevations of the High Knob Massif. It remains too early to forecast exact amounts, but the signal and pattern is very strong and has been consistent among ensembles and operational runs of medium range models for a strong orographic upslope event ( where snowfall is enhanced along the windward side of the mountain chain via forced convergence and upward rise of air on WNW-NW flow streaming from a Great Lake’s moisture source ).
As is almost always the case at this time of year, this will be an elevation biased event ( greatest snowfall amounts will be at the highest elevations ) with decreasing sticking & snow amounts as elevation decreases. In addition, at all elevations, more snow will tend to fall than is ever able to remain on the ground at any given time during the event.
Due to strong inverse orographics ( i.e., negative forcing ) lee of the major mountain barriers, snowfall and amounts are expected to be very limited downstream of the High Knob Massif-Tennessee Valley Divide and Blue Ridge.
As already noted above, please stay tuned for updates and possible changes in this scenario.
Meanwhile, the front end of this next storm system will again bring showers and thunderstorms with an enhanced to moderate risk from southern Kentucky through southern Tennessee. A slight risk is now outlooked across much of the Mountain Empire. Note that this could change again depending upon how activity develops Wednesday.
Stay tuned to NOAA Weather Radio and your favorite media sources for Watches and Warnings that may be needed later Wednesday into Wednesday night.
Nice orographic clouds during Monday afternoon ( March 3 ), with capping pilatus ( above ) and multiple wave clouds ( below ) on SW air flow trajectories streaming into & across the High Knob Massif.