Mostly clear. Areas of dense river valley fog. Large vertical temperature spread between colder mountain valleys and milder ridges-plateaus. Winds SW-WNW at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges and exposed plateaus. Temperatures varying from lower-middle 40s in colder mountain valleys to mid-upper 50s.
Monday Afternoon
Partly to mostly sunny. Winds NW-N at mostly less than 10 mph. Temperatures varying from upper 60s to lower 70s in upper elevations to the upper 70s to lower 80s.
Monday Night Into Tuesday Morning
Mostly clear. Large vertical temperature spread between colder mountain valleys and milder ridges. Light winds. Temperatures varying from 40 to 45 degrees in the colder mountain valleys to mid-upper 50s. Areas of dense river valley fog ( widespread along the Clinch & Cumberland ).
Tuesday Afternoon
Partly to mostly sunny. Unseasonably warm. Winds SW at 5-10 mph, with some higher gusts. Temperatures varying from 70s in upper elevations to the middle-upper 80s.
Tuesday Night Into Wednesday Morning
Partly cloudy during the evening with increasing high clouds overnight into morning. S-SW winds 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from 50s in cooler valleys to the 60s along exposed mountain ridges-plateaus.
An increasing chance for hit-miss showers and thunderstorms will be observed during late week into the upcoming weekend. Heavy rainfall will be possible by this weekend into next week ( note that any thunderstorm at this time of year can cause heavy local rain ). Stay tuned for later forecast updates on this potential.
Weather Discussion ( Warmer )
Although chilly nights will continue for a couple more days in mountain valleys, the pattern is shifting toward much warmer and gradually more humid conditions. Eventually, by later this week into the upcoming weekend, this will set the stage for showers and downpours in thunderstorms.
View From Powell Valley Overlook On Saturday – May 13, 2017
Temperatures into Mother’s Day morning dipped into the lower 40s in Clintwood and Norton and well down into the frosty 30s within high mountain valleys in the High Knob Massif ( other locations with 30s included Burkes Garden and Shady Valley ).
Large temperature differences between chilly mountain valleys and milder ridges & exposed plateaus will continue during morning hours of Monday and Tuesday mornings.
Whitewater Gushes In South Fork Gorge of High Knob Massif ( PM of May 13 )
Within complex mountain terrain surface dewpoints in valleys with access to the higher terrain are not that important during conditions favorable for drainage.
*Dewpoints and the cooling potential of air at the top of drainage basins are more important under this type of condition. That is why nocturnal temperatures can drop below dewpoints observed in lower-middle elevation valleys, and how high wetland valleys that may quickly reach near 100% RH can continue to cool during the night as lower dewpoint air aloft drains downward from high mountain ridges ( radiational cooling + lower dewpoint air = lower valley temps amid complex mountain terrain than often forecast ).
The time of year for widespread river valley fog is nearing, as folks living within the Clinch River Valley of Scott and Russell counties and the Powell River Valley, from East Stone Gap-Big Stone Gap into Lee County, know well. The drainage of cool air downward out of the High Knob Massif and Tennessee Valley Divide working to enhance fog formations ( the latent heat that releases with condensation adds warming to the air, countering some of the cooling to make these river valleys milder than their cold air drainage sources** ). A similar setting being applicable to the Cumberland and Russell Fork-Levisa Fork river valleys.
**There also appears to be a compressional warming factor after air vertically drops 1500 to 2000+ feet, even with drainage flows, as noted by valleys beneath the Black mountains in southeastern Kentucky which tend to be significantly milder than those on the Virginia side. More will be learned as a University Of Virginia’s College At Wise microclimatology field research project continues through coming seasons and years.
Like water, which gushes out of the high country, air drains into upper elevation valleys ( where it chills most ) and then continues downward through middle into lower elevations under the continuous force of gravity when conditions are favorable for nocturnal temperature inversions and development of cold air drainage flows.
European 51-Member Ensemble MEAN 500 MB Heights Forecast: Days 1-5
While a digging western USA upper trough will pump up or raise heights across the eastern USA ( warming air expands such that the height of any given isobaric surface is raised upward in the atmosphere ) during the next 5 days, a trend toward an eastward shift of storminess within the “clash” zone between the western trough-eastern ridge will occur.
European 51-Member Ensemble MEAN 500 MB Heights Forecast: Day 6-10
Hit or miss afternoon showers and thunderstorms will initially become possible due to daytime heating and the increase of instability; however, by this weekend into next week ( especially ) it appears that more widespread and organized showers-thunderstorms will become likely.
European 51-Member Ensemble MEAN 850 MB Temperatures: Days 1-5
At this time of year, as already observed this month, the positioning and potential stalling of any frontal zone will have to be monitored closely.
European 51-Member Ensemble MEAN 850 MB Temperatures: Days 6-10
Check back later this week for a better idea of timing on any potential heavy rainfall setting that may be upcoming.
ALERT For Ponding Of Water Along Roadways And For Dense Fog Development Into Middle Elevations Along And North Of The High Knob Massif Into Saturday AM
Run-off from moderate-heavy Friday rainfall has caused ponding of water along roadways. Slow down and be extra careful. In addition, low cloud bases are currently causing widespread dense fog at elevations above 2900 feet. Expect lowering of cloud bases overnight into Saturday Morning, to around or locally below the elevation of Wise, on rising northerly air flow along & north of the High Knob Massif.
Former Alerts:
The Storm Prediction Center Has Issued A Slight Risk For Severe Thunderstorm Development Thursday PM Through Thursday Night
Wind damage will be the primary threat with any strong to severe thunderstorms Thursday Afternoon & Thursday Night. Otherwise, heavy rainfall will be a concern from Thursday Evening Through Friday Night. Folks living and/or driving through low lying and flood prone locations should remain alert for ponding of water and strong rises on streams. Never drive through a flooded road, TURN AROUND and DO NOT DROWN.
While a Flash Flood Watch is officially in effect through Friday for Dickenson and Buchanan counties, adjacent locations across Wise, Scott, Lee, and Russell counties will also be at risk for strong rises on creeks and rivers.
Stay tuned to NOAA Weather Radio and your favorite media sources for possible warnings and additional watches that may be needed through Friday.
Remainder Of Thursday Afternoon
Partly-mostly cloudy. Chance of showers & thunderstorms, especially in portions of Dickenson and Buchanan counties. Gusty. SW-WNW winds at 10 to 20 mph, with higher gusts. Temperatures varying from 60s in upper elevations of the High Knob Massif to the upper 70s to lower 80s.
Thursday Evening Through Friday Morning
Showers & thunderstorms becoming likely. Some storms could be strong to locally severe. Downpours of heavy rain. Winds becoming SSE-SSW and diminishing overnight into morning. Areas of dense fog. Unseasonably warm with temperatures widespread in the 50s to around 60 degrees.
Mid-Morning Friday Through Friday Afternoon
Showers & thunderstorms. Locally heavy rainfall possible. Light and variable winds becoming northerly. Low clouds with widespread dense fog in upper elevations ( orographic cap clouds ). Temperatures varying from 50s at the upper elevations to the 60s within middle and lower elevations.
*Lowering cloud bases and dense fog will become a factor at middle to upper elevations during Friday Night into Saturday AM, with the potential for cloud bases to drop downward across the Wise & Sandy Ridge plateaus ( to around or below 2500 feet ) on upsloping northerly air flow toward the High Knob Massif.
Friday Night Into Saturday Morning
Showers to drizzle. Turning chilly. Low clouds with dense fog from around the elevation of Wise upward in elevation. Winds NNW to NNE at 5-15 mph, with higher gusts. Temps dropping into 40s to around 50 degrees ( near 40 degrees at summit levels of the High Knob Massif ). Wind chill factors in 30s and 40s ( coldest at highest elevations ).
Saturday Morning Through The Afternoon
Low clouds-fog-drizzle during the morning ( especially at higher elevations ) giving way to partly-mostly sunny skies during the afternoon. Winds NW-N at 5-10 mph with higher gusts. Temperatures varying from the lower-middle 50s in upper elevations to the 60s ( warmer to the south within lower elevations of the Great Valley ).
Saturday Night Into Sunday Morning
Large vertical temperature spread developing between colder valleys and exposed mountain ridges & plateaus. Mostly clear evening skies, then increasing clouds possible overnight into morning. Winds becoming WSW to WNW at 5 to 15 mph, with higher gusts, along exposed middle-upper elevation mountain ridges. Generally light valley winds. Temps varying from 30s to lower 40s in mountain valleys to the upper 40s to low-mid 50s.
Weather Discussion ( Changeable )
Changeable is probably the best way to describe weather conditions through upcoming days, with the first order of business being a developing cluster of thunderstorms that will move across the mountains Thursday evening.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Although temperatures are mostly in the 60s ( upper elevations ) and 70s ( middle elevations ) to lower 80s ( lower elevations and or places under downsloping air flow ), there is a notable haze and increase in low-level moisture in advance of developing thunder-storms upstream of the mountains.
Storm Prediction Center Risk Regions
A few storms currently have warnings on them in Kentucky and this will be a trend to watch through the remainder of this afternoon into this Thursday evening as a cluster of thunderstorms ( MCS or Mesoscale Convective System ) comes together over the foothills and mountains.
Jackson Kentucky Doppler At 4:22 PM Thursday ( May 11 )
Cloud tops are growing vertically and expanding upstream, and while a wind damage potential does exist the threat for heavy rainfall will certainly be a concern with more rounds of showers-thunderstorms expected Friday.
NASA Visible With Watch-Warning Overlay
With convection it is always difficult to pinpoint places receiving heaviest rain amounts, but the signal is clear.
NAM 12 KM Model Rainfall Forecast Next 60-Hours
Locally heavy rainfall amounts are likely through Friday.
NAM 3 KM Model Total Precipitation Forecast To 8 AM Saturday – May 13
Following a cooling trend behind all this mess into this weekend, with chilly temperatures in mountain valleys being notable Saturday evening into Mother’s Day morn, major warming will become the theme next week.
European 51-Member Ensemble MEAN 500 MB Height Anomalies: Days 6 to 10
A big trough developing over the western USA will pump up heights across the eastern states and generate anomalously warm conditions for a good portion of next week.
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: Days 6 to 10
*Nights may continue to be cool in mountain valleys if winds are light, but days are clearly trending toward being unseasonably warm for this time of year during next week.
A Heavy Rainfall And Thundestorm Cluster Setup Is Being Monitored For Thursday Night Through Friday Night Into Saturday Morning.
Former ALERTS:
ALERT For Frost & Freezing Conditions In Colder Mountain Valleys Into Monday Morning
Low temperatures will drop into the 30s within many mountain valleys overnight into Monday morning, with upper 30s to lower 40s on exposed middle-upper elevation mountain ridges-plateaus. The coldest mountain valleys will drop into the 20s to lower 30s, mainly at elevations above 2000 to 3000 feet.
Overnight Into Monday Morning
Becoming clear. Chilly. NW winds 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges. Light valley winds. Areas of frost, most widespread in the colder, sheltered valleys. Temperatures varying from 20s to lower 30s in colder valleys ( at mid-upper elevations ) to the upper 30s to lower 40s ( exposed mountain ridges ).
Monday Afternoon
Mostly sunny ( beautiful blue skies ). Milder. WNW to NW winds 5-15 mph, with higher gusts. Temperatures varying from 50s in upper elevations to the lower-middle 60s.
Monday Night Into Tuesday Morning
Partly to mostly clear during the evening, then increasing clouds with a chance of showers-thunderstorms overnight into morning. Rapid evening temp drop in valleys before rising overnight. NW-W winds 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges. Temperatures varying from 30s to lower 40s in coldest valleys ( before rising ) to the 40s to lower 50s.
Tuesday Afternoon
Partly to mostly cloudy. Warmer A chance of showers and thunderstorms. Winds WSW to WNW at 10-20 mph, with higher gusts. Temps varying from the 60s to lower 70s.
Tuesday Night Into Wednesday
Partly to mostly cloudy. Mild. A chance of showers and thunderstorms. Winds WSW-WNW at 10-20 mph, with higher gusts on mid-upper elevation mountain ridges- plateaus. Temperatures widespread in the 50s to lower-middle 60s.
Wednesday Afternoon
Partly cloudy. Warm. A slight chance of a hit-miss shower or thunderstorm. Winds SW-WNW at 5-15 mph, with higher gusts. Temperatures varying from upper 60s to lower 70s at highest elevations to the upper 70s to lower 80s.
Weather Discussion ( Unsettled )
Monday Evening Update
A frosty morning greeted colder mountain valleys with low temperatures varying from the upper 20s to the middle 30s.
The low temperature reached 34 degrees in Clintwood.
Big Cherry Wetland Valley Temperature-RH
The coldest low temperature recorded in the area occurred within high valleys of the High Knob Massif, where colder valleys dropped into the upper 20s. The time spent below freezing was limited by abundant clouds into the early overnight, followed by strong predawn temperature drops.
The MEAN low temperature observed at the Big Cherry Wetland Valley 4 site has been 38.4 degrees so far during the month of May.
Previous Discussion
A chilly weekend was observed across the mountains with snow pouring down at the summit level of the High Knob Massif during Saturday. Although generally not sticking, with temps around or above freezing at 4200 feet, such was not the case upon climbing upward in elevation to the very highest summits where up to 7″ of snow depth accumulated on top of Mount LeConte in the Smokies.
Wind chills dropped into the 10s atop the High Knob Massif to put a true wintry feel into the air. Clearing skies by Sunday morning allowed air temperatures to reach the 20s to around 30 degrees.
High Knob Massif Webcam – University Of Virginia’s College At Wise
A milder but gusty Sunday afternoon graced the mountain landscape beneath fair weather cumulus clouds. This sets the stage for a cold night in mountain valleys as winds decrease overnight into morning.
Frost and freezing conditions will occur in colder locations versus a frost-free environment across exposed mid-upper elevations and the warmer valleys. If you are uncertain about your location, it would be best to bring any tender plants not already in the ground inside for the night.
NAM 12 KM Model Total Rainfall Forecast NEXT 60 Hours
The focus then shifts toward a band of showers and thunderstorms that will be developing amid isentropic lifting along and northeast of a warm frontal zone by Tuesday into Wednesday. The European Model group forecasts the heaviest rainfall corridor to set up from southern Ohio across central-southern West Virginia, northeast of the higher mountain terrain of the famed Mountain Empire. Climatologically, this is favored but until it actually develops the exact corridor for heavy rainfall and thunderstorms can not be certain. Thus, a heavy rainfall and thunderstorm cluster setup is being monitored ( as noted in my headlines at the top ).
European 51-Member Ensemble MEAN 500 MB Height Anomalies Forecast
In general the pattern will be unsettled and cooler than average for this time of year, especially from late week into early next week. The 51-Member European Ensemble MEAN is forecasting a general 2.00″ to 5.00″ of rainfall along the southern-central Appalachians during the next couple of weeks ( through the middle week of May ). Since this is “basin-average” rainfall amounts, during the convective season this means the potential for locally higher totals will have to be respected.
An Alert For Frost & Freezing Conditions May Be Needed Across Much Of The Area By Monday Morning
*Temperatures around or below freezing will be possible on highest peaks into Saturday morning, and in high valleys and peaks on Sunday morning.
Overnight Into Friday Morning
Showers with a chance of thunder. Winds shifting SW to WNW at 5 to 15 mph, with higher gusts. Temperatures dropping into low-mid 40s at highest elevations to the upper 40s to mid 50s. Low clouds ( dense fog ) in upper elevations.
Friday Afternoon
Showers. Low clouds & chilly. Winds SSW-W at 5-15 mph, with higher gusts. Temperatures rising very little or slowly falling in the 40s ( upper elevations ) and middle 50s to lower 60s at middle-lower elevations by late afternoon.
Friday Night Into Saturday Morning
Rain & showers. Turning colder. Rain becoming mixed with or turning to snow at elevations above 3500 feet overnight into morning. WNW to NW winds 10-20 mph, with higher gusts. Temperatures varying from around freezing at highest elevations to low-mid 40s. Wind chill factors within the 20s and 30s, except 10s in gusts on highest summits ( above 3600 feet ). Orographic clouds-dense fog upper elevations ( becoming freezing fog highest peaks ).
Saturday Mid-Morning To Mid-Day
A break possible in showers. Partly to mostly cloudy. Winds WNW-NW 5-15 mph, with higher gusts. Temps in the 30s ( upper elevations ) to the 40s ( low-middle elevations ).
Saturday Afternoon
Low clouds. Showers redeveloping. Rain and/or snow mix on highest peaks. Local small hail possible. Winds WNW-NW at 10-20 mph, with higher gusts. Temps varying from 30s in upper elevations to middle 40s to lower 50s. Dense fog at upper elevations. Wind chills varying from 20s in upper elevations to the 30s to around 40 degrees.
Saturday Night Into Sunday Morning
Low clouds. Showers tapering to drizzle before ending. Clearing possible by morning. Cold. Winds W-NW at 5-15 mph, with some higher gusts. Temperatures varying from 20s to around 30 degrees on highest peaks and high valleys to the upper 30s to around 40 degrees. Wind chills varying from 10s & 20s at highest elevations to the 30s. Dense fog in upper elevations ( freezing fog highest peaks ) giving way to clearing toward morning.
Sunday Afternoon
Mostly sunny ( deep blue ) skies. Gusty & chilly. Winds WNW-NW at 10-20 mph, with higher gusts. Temperatures varying from low-mid 40s at highest elevations to the middle-upper 50s. Wind chills in the 30s and 40s across middle-upper elevation mountain ridges.
Weather Discussion ( Chilly & Wet )
An unseasonably cold, for this time of year, pattern is taking shape for this weekend into much of next week.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Dramatic cloud formations, as often is the case when SE winds blow across the High Knob Massif, were on display throughout much of Thursday ( May 4 ).
A persistent standing wave on the SE flow stood for hour after hour as strong-gusty winds blew upward across the high country. Although changing specific appearance at any given moment, the general cloud formation remained consistent through time.
High Knob Massif Webcam – University Of Virginia’s College At Wise
While below freezing air and even flakes of snow are not uncommon during May, especially in the high country, the upcoming pattern is going to be unseasonably cool during the next 10 days ( in the mean ).
Majestic Spring Afternoon In Big Cherry Wetland Valley – May 3, 2017
Temperatures in the 30s have occurred in high valleys within the High Knob Massif recently during morning hours of April 26 and May 3; however, temperatures in the 20s within high valleys will likely occur by early next week ( perhaps as early as Sunday AM if skies should clear before sunrise ). This is a given.
The more critical forecast will be for lower-middle elevations, even the thermal zone orchard belt, where some frost sensitive crops may already be planted. Stay tuned for updates.
European 51-Member Ensemble MEAN 500 MB Height Anomalies: Days 1-5
The European Model group ensemble MEAN is showing troughing across the eastern USA, with a general Omega Blocking feature that allows the pattern to reload next week just as it appears that warming might take hold.
European 51-Member Ensemble MEAN 500 MB Height Anomalies: Days 6-10
This results in an unseasonably chilly May pattern.
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: Days 1-5
If this forecast verifies, unseasonably cold air for this time of year will continue through the first half of May. Timing when frost and freezing conditions occurs will be the main forecast challenge upcoming.
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: Days 6-10
The Storm Prediction Center Has Issued A Risk For Severe Thunderstorm Development Monday
Storm Prediction Center Risk Regions For Monday – May 1, 2017
*An Enhanced Risk for Severe Thunderstorm Development will exist East to Northeast of the Cumberland Mountains, with the potential for upscale growth into a damaging squall line in locations along and east of the Blue Ridge.
Stay tuned to NOAA Weather Radio and your favorite media sources for any possible watches or warnings that may be issued during Monday.
Overnight Into Monday Morning
Mostly cloudy. Windy & mild with a chance of showers. SSE-SSW winds 5-15 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. Winds S-SW 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures widespread in the 60s.
Monday Morning Through Monday Afternoon
Showers & thunderstorms becoming likely. Some storms could be strong to locally severe. Windy. SW to W winds at 15-25 mph, with higher gusts ( to 40+ mph ). Temperatures varying from low-mid 60s in upper elevations to the lower-middle 70s. Period of low clouds ( dense fog ) at the highest elevations.
Monday Night Into Tuesday Morning
Partly-mostly cloudy skies giving way to mostly clear conditions by morning. Windy. SW-W winds 10-20 mph, with higher gusts, along mid-upper elevation mountain ridges and plateaus. Temperatures varying from low 40s upper elevations to the upper 40s to lower 50 degrees.
Tuesday Afternoon
Partly to mostly sunny ( blue ) skies. Cooler & windy. WSW to W winds 10-20 mph, with higher gusts. Temperatures varying from 50s in upper elevation to 60s to around 70 degrees at lower-middle elevations.
Tuesday Night Into Wednesday Morning
Mostly clear & chilly. Winds shifting NW at 5-15 mph and decreasing toward morning on all but the highest mountain ridges. Temperatures varying from 30s in upper elevations, and the coldest valleys, to the 40s. Areas of river valley fog.
Weather Discussion ( Late Spring )
The arrival of May marks the final month of Meteorological Spring, and a shift into a cooler weather pattern in wake of unseasonable warmth during the second half of April.
Wild Geranium ( Geranium spp. ) On April 27, 2017
April 2017 ended having produced a general 6.00″ to 10.00″ of rain along the Cumberland Mountains.
Swallowtail Butterfly On A Wild Azalea ( Rhododendron periclymenoides )
This wet pattern also looks to continue as temperatures chill downward during the first week or so of May.
European Ensemble MEAN 500 MB Height Anomalies: Days 1-5
The 51-Member European Ensemble MEAN is forecasting a upper air trough to dominate in the mean during the first 10 days of May, with basin average rainfall totals in the 3.00″ to 5.00″ range.
*Localized variations in amounts could be significantly greater, with both lesser and higher precipitation totals being possible during this period.
European Ensemble MEAN 500 MB Height Anomalies: Days 6-10
This results in a rather dramatic shift toward cooler than average temperatures for this time of year.
European Ensemble MEAN 850 MB Temp Anomalies: Days 1-5
Much below average temperatures is currently being forecast during the May 4-10 period.
*Some model runs have actually shown the air cold enough for snow to fall at highest elevations along the central-southern Appalachians. That remains to be seen, of course, but would certainly not be impossible ( i.e., it has occurred many times during past May’s ).
European Ensemble MEAN 850 MB Temp Anomalies: Days 6-10
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.
Storm Prediction Center Day 1 Risk RegionsStorm Prediction Center Discussion
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.
High Knob Massif Webcam – University Of Virginia’s College At Wise
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.
Regional Doppler Composite
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.
NASA Water Vapor Image At 3:45 PM on Saturday ( April 22, 2017 )
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 ).
NAM 12 KM Model – Rainfall Still To Come Through Sunday Afternoon
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.”
NAM 3 KM Model – Rainfall Still To Come Through Sunday Afternoon
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.
Saturday Afternoon
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.
Large-flowered Trillium ( Trillium grandiflorum ) – Lower Elevations on April 12, 2017
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 ).
NAM 3 KM Model Total Rainfall Forecast Up To 8:00 PM Saturday – April 15, 2017
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.
Tuesday Afternoon
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.
Wednesday Afternoon
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 ).
Looking Across Sprawling Top of High Knob Massif To Mount Rogers-Whitetop
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 ).
Snow Drifts Along High Mountain Ridges In High Knob Massif – PM of April 7
Spring continues to progress, despite this wintry blast, especially within lower-middle elevations which missed accumulating snowfall ( at elevations below 3000 feet ).
Wild Geraniums ( Geranium spp. ) Beginning To Bloom
A chance for hit-miss showers and thunderstorms, with large variations in rainfall amounts, will be possible by Tuesday afternoon into Tuesday Night.
NAM 3 KM Model Total Rainfall Forecast To 8:00 AM Wednesday ( April 12 )
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.
European 51-Member MEAN 500 MB Height Anomalies Forecast: Days 6-10
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.
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: Days 6-10
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.
Friday Afternoon
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 ).
Saturday Afternoon
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.
Eagle Knob of High Knob Massif At 5:16 PM Thursday – April 6, 2017
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 ).
Black Mountain Mesonet – Sample Hour Ending At 10:15 PM ( April 6 )
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.
Black Mountain Mesonet – Sample Hour Ending At 9:30 PM Thursday ( April 6 )
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.
NAM 3 KM Model 850 MB Temp Forecast At Noon Friday – April 7, 2017
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.
