Alert For Increasing Showers And Thunderstorms Thursday Into Friday As The Remnants Of Harvey Approach And They Transform Into An Extratropical Storm System ( i.e., With An Increasingly Cold Core )
While the heaviest, widespread rainfall totals look most likely across western & central portions of Kentucky-Tennessee the potential exists for orographically enhanced rainfall amounts along the Blue Ridge and within favored upslope areas of the Cumberland Mountains & Cumberland Plateau.
The Storm Prediction Center Has Issued A Slight Risk For Severe Thunderstorm Development As Remnants Of Harvey Impact The Southern Appalachians
The main storm threat will be wind damage, to include an isolated tornado risk due to strong low-level wind shear driven by Harvey’s remnant circulation. A notable & increasing temperature gradient will develop late Friday into Saturday as an increasingly cold core develops with transformation into an extratropical cyclone.
Storm Prediction Center Forecast Severe Weather Risk Regions
Very chilly conditions are expected to develop over the mountains by Saturday as extratropical Harvey draws unseasonably cool air into the Cumberland & Allegheny mountain ranges, which look to experience the burnt of chilly air Saturday into Saturday Night.
Temperatures Saturday will struggle in the 50s at the elevations of Norton-Wise and may hold in the 40s to near 50 degrees at upper elevations within the High Knob Massif during the day, where conditions will feel even cooler due to wind chills.
Overnight Into Wednesday Morning
Partly to mostly cloudy. Areas of valley fog. Light winds. Temperatures in the 50s to around 60 degrees, except the upper 40s to low 50s within colder high valleys at upper elevations in the High Knob Massif.
Wednesday Afternoon
Partly to mostly cloudy. More humid. A chance for showers and thunderstorms by mid-late afternoon into the evening. Winds generally light and variable. Temperatures varying from upper 60s to lower 70s at upper elevations to the upper 70s to lower 80s.
Wednesday Night Into Thursday Morning
Showers & thunderstorms becoming likely by morning. Downpours possible. Winds variable at generally less than 10 mph. Temps varying from the upper 50s to the middle 60s. Areas of dense fog, especially at high elevations.
Thursday Afternoon
A chance of showers. Thunder possible. Humid. Winds SE-SSE at 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures mainly in the 60s to near 70 degrees ( around 60 degrees at highest elevations ).
Thursday Night Into Friday Morning
Showers & thunderstorms. Locally heavy rainfall totals. Humid. Winds SE to S and increasing to 10-20 mph, with gusts over 30 mph at high elevations, by morning. Low clouds with dense fog at upper elevations. Temperatures widespread in the 60s.
Friday Afternoon
Showers & thunderstorms. Locally heavy rainfall totals. Humid. Winds SSE-SSW at 15-25 mph, with higher gusts. Temperatures from the upper 60s to the upper 70s ( coolest at the highest elevations ). Low clouds and dense fog at the highest elevations.
Friday Night Into Saturday Morning
Gusty with rain and showers. Turning much cooler. Winds becoming S-SW at 10-20 mph, with higher gusts, on middle to upper elevation mountain ridges-plateaus. Low clouds with dense fog across the higher elevations. Temperatures dropping into the low-mid 40s to mid 50s ( coolest highest elevations ). Warmer south into the Great Valley.
Saturday Morning Through Afternoon
Low clouds with dense fog at high elevations. Chilly. A chance of drizzle or light showers. Winds SW-W at 5-15 mph, with higher gusts. Temperatures near steady or only slowing rising in the low-mid 40s to mid-upper 50s, coldest at upper elevations. Wind chill factors in the 30s & 40s to around 50 degrees, coldest at highest elevations.
A very complicated extended range period is upcoming as a deep, autumnal trough digs into the USA with potential for new tropical development in the Gulf of Mexico. Meanwhile, a Cape Verde born disturbance may become a major Hurricane as it approaches the Leeward Islands and Caribbean in a week to ten days.
Weather Discussion ( Wild Times )
Thursday Evening Update
A very humid air mass has now engulfed the mountains, with orographic clouds forming along the High Knob Massif all day ( afternoon temperatures hovering in the 60 to 62 degree range on Eagle Knob ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
Heavy showers, with torrential downpours, occurred during the afternoon with 0.50″ to 1.00″ amounts in local areas. At one point rain was falling so heavily along U.S. 23, from the Powell Valley Overlook area into Norton, that some had to pull off the highway. A signal that upcoming rain will have a tropical, downpour nature as the main system arrives.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The forecast appears to be on target, with the first round of organized activity expected to overspread the mountains by the predawn-morning hours of Friday as winds increase at higher elevations, then winds increase across the entire area during the daylight hours of Friday.
HRRR Model Future Doppler At 4:00 AM on Friday – September 1, 2017
Any breaks Friday in the overcast could help fuel formation of strong-severe thunderstorms before the focus shifts to a influx of increasingly cool air, low clouds, showers-drizzle into Saturday.
One aspect to note for Friday is that narrow bands of convergence, much like feeder bands that come ashore from such a system, are likely to develop with cross-isobaric ( ageostrophic ) flow due to both Harvey’s large-scale circulation and friction ( terrain driven ) to support zones of higher impact. It is not possible to tell exactly where these will form until they begin to develop, so remain alert and tuned to NOAA Weather Radio and your favorite media out-lets for any warnings or advisories that may be needed.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Meanwhile, enjoy a tropical skies filled sunset.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Previous Discussion
A wild weather roller coaster ride is upcoming through the next 1-2 weeks as all sorts of havoc tries to play out across this region of the world. The mega-disaster of Harvey being the start of what appears to be an extreme weather pattern for this time of year in the eastern USA.
National Hurricane Center Forecast Track of Harvey Remnants
There has been a gradual but important eastward shift in the forecast track of Harvey’s remnants into Friday and Saturday, with clear indications now that it will become incorporated into the jet stream and transformed into an extratropical rain storm; thus, the increasing amount of chilly air that will develop due to dynamically forced cool-ing with rising air and advection of cool air to the north that will wrap around the circulation by Saturday.
Cool here means REALLY cool for this time of year, with temperatures Saturday having the potential to remain in the 40s all day in the high country of the High Knob Massif and struggling to rise through the 50s in Wise ( milder at lower elevations, below 2000 feet, and to the south into the Great Valley of eastern Tennessee and southwest Virginia ).
Spaghetti Model Cluster Forecast For Harvey – 2 AM Model Run Wednesday
Enough spread in the model spaghetti cluster remains for there to continue to be an eastward shift as the remnants reach the latitude of Kentucky and this region.
NAM 12 KM Model Total Precipitation Forecast – Next 84 Hours
Regardless of the exact track, increasing air flow into the mountains will allow for orographic forcing to develop and this will help to increase rainfall amounts by Thursday into Friday. Given a wet August in the Cumberland Mountains, this will bear close watching. The windward slopes of the Blue Ridge will be favorable for the heaviest orographic rains, with several inches or more being possible.
European Model Mean Sea Level Pressure Forecast – 8 PM September 6
The European Model has been on a “hot streak” lately, to the great agony of everyone in southeastern Texas, so it is hard to deny the operational and many ensembles which show a new low developing in the Gulf by the early-middle parts of next week ( this has now been shown for a couple days ).
European Model 850 MB Temp Anomalies Forecast: Days 6-10
At the same time, an anomalously deep upper air trough for early September has now been shown for days and days to dig deeply into the central-eastern USA by the middle to later portions of next week.
Collectively, a wild setting being shown. Although early September is the climatological peak of Hurricane season, it is also the beginning of Meteorological Autumn, a season that climatically is the driest within the Mountain Empire.
With luck this big trough could dig deeply enough to deflect any developing tropical systems away from the USA, but if not then big problems could arise for more than just coastal locales. It is simply too early to know, but certainly something that all forecasters will be closely following into next week.
Thoughts & prayers to our Texas friends.
*While Tropical Storm Claudette still holds the continental USA record for the most rain to fall within 24-hours ( 42.00″ fell on Alvin, Texas just south of Houston in July 1979 ), Harvey now appears to have shattered the record for the most rain to fall during a single storm event ( with a preliminary storm total of 51.88″ reported in the heaviest location ).
An increasing chance for widespread showers and thunderstorms is being watched for mid-late week into this weekend as moisture from Harvey begins to finally lift north and east.
Overnight Into Monday Morning
High cloudiness. Areas of valley fog. Winds SSE-S at 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures varying from low-mid 50s in cooler mountain valleys and highest ridges to the lower 60s.
Remainder of Monday Afternoon
Cloudy ( mid-high clouds ). Small chance of showers, mainly west of the mountains in SE Kentucky. Light ESE-SSE winds generally less than 10 mph. Temps varying from the lower 60s within upper elevations to the lower 70s.
Monday Night Into Tuesday Morning
Mostly cloudy. Small chance of showers, especially to the southeast toward Mount Rogers-Whitetop. Areas of river valley fog. Winds E-SE at 5 to 15 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from the upper 40s to low 50s at upper elevations in the High Knob Massif to the mid-upper 50s.
Tuesday Afternoon
Partly to mostly cloudy. Chance of hit-miss showers and thunderstorms. Light winds. Temps varying from low-mid 60s in upper elevations to the low-mid 70s ( warmer south into the Great Valley ).
Tuesday Night Into Wednesday Morning
Partly to mostly cloudy. Areas of valley fog. Light winds. Temperatures in the 50s to around 60 degrees, except the upper 40s to low 50s within colder high valleys at upper elevations in the High Knob Massif.
Wednesday Afternoon
Partly to mostly cloudy. More humid. A chance for showers and thunderstorms by mid-late afternoon into the evening. Winds generally light and variable. Temperatures varying from mid-upper 60s at upper elevations to the mid-upper 70s to around 80 degrees.
Weather Discussion ( In The Middle )
Monday Evening Update
A solid mid-high altitude overcast has dominated Monday with abundant clouds streaming northeast from tropical storm Harvey. This held temperatures in the 60s and 70s, varying from lower 60s in the High Knob Massif to the low 70s in Clintwood ( 71.7 degree official maximum ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
This update continues to highlight low rain chances over the mountains tonight, with a lesser chance for showers even toward the Blue Ridge as potential Irma along the Atlantic Coast struggles to develop within wind shear generated by Harvey and a polar jet stream.
Based upon late Monday evening readings, overnight temperatures in the high country of the High Knob Massif have been dropped a little from my previous forecast to account for lowering dewpoints and some possible over-night cloud breaks ( and decreasing predawn winds ).
Humidity + some instability will then offer a chance for localized shower-thunderstorm development Tuesday afternoon across the Cumberland Mountains.
NAM 12 KM Model Total Rainfall Forecast Next 84 Hours
Moisture related to the remnants of Harvey may begin to impact the mountain region by later Wednesday into the Thursday-Friday-Saturday period, with rainfall amounts and details yet to be determined.
Moisture from Harvey is looking increasingly like it will have some impact upon the area by late week-this weekend, per the latest ensemble means.
GFS Model Total Rainfall Forecast Next 132 Hours
While it has been a wet August in the mountains, with 7.00″ to 9.00″ widespread within the High Knob Massif – City of Norton and Big Stone Gap Water Plant area – just imagine that 3 to 4 times this much has fallen in the past few days over the area centered on Houston, Texas.
Month-To-Date Rainfall Estimated-Observed – Ending 8 AM August 28, 2017Estimated Rainfall Past 7 Days – Houston Tx Area – Ending 8 AM August 28, 2017
Previous Discussion
A few local downpours of rain, with lightning & thunder, developed Sunday to close out a seasonally cool weekend in the Cumberland Mountains. This as the mountain region is safely in the middle between the terrible impact of Harvey along the Gulf Coast of Texas and a developing tropical system near the Atlantic Coast.
Low temperatures of 40 to 45 degrees were reported within colder mountain valleys of upper elevations, with 50s being widespread elsewhere in the mountain area, during recent days.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The heaviest rain developed along the U.S. 23 corridor between the City of Norton and Big Stone Gap.
NASA Visible Satellite Image At 6:00 PM on Sunday – August 27, 2017
Doppler radar estimated locally more than 1.00″ of rain near and just northeast of Big Stone Gap ( most of which fell within 1 hour ).
Doppler 1-Hour Estimated Rainfall Ending At 6:14 PM on August 27, 2017
With so much air rising over the remnants of Harvey and along the Tidewater of the southeastern USA it is likely any local rainfall will remain limited into mid-week ( due to synoptic-scale subsidence ). Meanwhile, there will be an abundance of high clouds over the area which are being sheared off the top of Harvey’s upper-level outflow.
USA Infrared Satellite Image At 3:15 AM on August 28, 2017
Some adjustments in cloud cover, temperatures, and the chance for showers may be needed depending upon the track of Harvey’s remnants during mid-late week.
European Model Mean Sea Level Pressure Forecast – 8:00 PM Friday ( Sept 1 )
The best chance for rain looks to be late this week into the weekend, when remnants of Harvey may finally get picked up by the jet stream. Stay tuned for updates.
A much cooler, autumnal air mass will be felt in coming days with chilly nights in mountain valleys ( and by day at high elevations ). While most places will drop into the range of upper 40s to middle 50s, colder mountain valleys at upper elevations will drop into the 40-45 degree range from the High Knob Massif to Burkes Garden. Cool nights are expected to continue into this weekend.
Overnight Into Wednesday Morning
Showers & thunderstorms into the early-mid overnight, local downpours likely, before tapering to showers. Winds SW 5 to 15 mph, with higher gusts, shifting northerly and decreasing into morning. Areas of dense fog, especially at highest elevations ( orographic clouds ). Temps widespread in the 60s ( dropping to around 60 degrees high elevations ).
Wednesday Morning Through The Afternoon
Any showers ending by mid-morning to mid-day, then becoming partly cloudy. Cooler. NNW-N winds 5-10 mph. Temps varying from low-mid 60s at highest elevations to the low-middle 70s ( warmer south into the Great Valley ).
Wednesday Night Into Thursday Morning
Becoming clear and chilly. Areas of dense valley fog. Winds NW-N at 5-10 mph on mid-upper elevation mountain ridges. Temperatures widespread in the 50s, except mid-upper 40s to lower 50s in upper elevations.
Thursday Afternoon
Partly cloudy. Beautiful blue skies. NW-N winds 5-10 mph, with some higher gusts along higher ridges. Temperatures varying from upper 50s to lower 60s at highest elevations to the upper 60s to lower 70s ( warmer into the Great Valley ).
Thursday Night Into Friday Morning
Clear & chilly. Areas of dense valley fog. Light N-NE winds along mid-upper elevation mountain ridges. Large vertical temperature spread between colder valleys-exposed ridges. Temperatures in the upper 40s to middle 50s, except 39 to 44 degrees in colder valleys above 2700-3000 feet.
Friday Afternoon
Partly to mostly sunny. Seasonably cool. N-NE winds 5 to 10 mph. Temperatures varying from low-mid 60s in upper elevations to the lower-middle 70s ( warmer south into the Great Valley ).
Friday Night Into Saturday Morning
Mostly clear & chilly. Areas of dense valley fog. Light NE to ENE winds along mid-upper elevation ridges. Large vertical temperature spread between colder valleys-exposed ridges. Temperatures in the upper 40s to middle 50s, except 40 to 45 degrees in colder valleys above 2700-3000 feet.
The inland track of remnant moisture from tropical activity in the Gulf of Mexico is being monitored for later next week. Stay tuned for updates.
A strong early autumn-like cold front is expected to bring a refreshing air mass change to the mountain region through coming days. While this will be notable at high elevations even during the day, it will be especially noticed during the night-time periods in mountain valleys.
Nocturnal dense fog formation will be likely in lower elevation valleys, especially along streams & rivers, with released latent heat of condensation helping keep temps milder ( upper 40s to lower 50s ) than locations with valley floors above 2700 to 3000 feet where lower dewpoints will enhance cold air drainage.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5
A very strong cool signal is indicated for the next 5 days. While below average temperatures are likely to continue into the 6-10 day period, there is increasing uncertainty, due mainly to tropical activity over the Gulf of Mexico, regarding mid-late next week ( Aug 30-Sept 2 ).
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 6-10
The strength and position of a trough over the eastern USA will play an important role in the eventual inland move-ment of tropical moisture over the Gulf of Mexico.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
Weather Conditions Monday Will Be Influenced By A Solar Eclipse Between 1:00 PM and 4:00 PM, With A Temperature Drop Of 5 to 15 Degrees ( F ) Expected.
The Storm Prediction Center Has Issued A Marginal To Slight Risk Of Severe Thunderstorm Development For Tuesday Into Wednesday For Locations Along And West Of The Cumberland Mountains.
A Heavy Rainfall Potential Will Also Exist From Late Tuesday Into Wednesday Along And In Advance Of A Strong Cold Front.
Overnight Into Monday Morning
Partly cloudy. Areas of dense valley fog. Light SSE-SSW winds 5-10 mph, with higher gusts on mid-upper elevation mountain ridges. Calm valley winds. Temps varying from upper 50s to lower 60s in cooler valleys to the upper 60s to lower 70s on exposed mountain ridges.
Monday Afternoon & Solar Eclipse
Partly to mostly cloudy. Increasing darkness from 1:00 PM to 2:35 PM, then increasing daylight to 4:00 PM. Chance of a localized hit-miss shower or thunderstorm. Light SSE-SSW winds. Temps varying from the lower 70s to the lower 80s into early afternoon, then dropping 5-15 degrees depending upon the location and elevation before late afternoon rises occur prior to sunset.
Monday Night Into Tuesday Morning
Partly to mostly clear. Areas of valley fog. SSW-SW winds 5 to 15 mph, with higher gusts, along middle-upper elevation mountain ridges and plateaus. Temperatures mostly in the 60s, with some 50s possible in coolest mountain valleys.
Tuesday Afternoon
Partly-mostly cloudy. Chance of showers & thunderstorms. Downpours possible. SSW-SW winds 5-15 mph, with higher gusts. Temperatures varying from the low-mid 70s to the lower-middle 80s ( coolest in upper elevations ).
Tuesday Night Into Wednesday Morning
Showers & downpours in thunderstorms becoming likely. Heavy rainfall totals possible. SW-WSW winds 5-15 mph with higher gusts. Areas of fog, especially at the highest elevations. Temperatures widespread in the 60s.
Weather Discussion ( Solar Eclipse )
*Reference this section for a recap of the Eclipse:
Weather conditions at the beginning of this forecast period will be influenced by a rare solar eclipse, reaching around 96% totality in Norton-Wise ( 95% in Clintwood ) by 2:35 PM on Monday ( August 21, 2017 ).
Solar Eclipse Timing City of Norton-Wise
Begins: 1:07 PM
Peak: 2.35 PM ( 96% Totality )
Ends: 3:58 PM
*Since the sun will never be completely blocked by the moon at this latitude, DO NOT LOOK AT THE SUN WITHOUT PROTECTIVE, OFFICIAL ISO-RATED GLASSES.
A significant amount of cloud development will be possible by early afternoon over the Cumberland Mountains, such that some locations will likely have viewing problems. A small chance for local hit-miss showers-thunderstorms is also in my forecast.
Expect temperatures to drop 5 to 15 degrees between 1:00 PM and 2:45 PM, with precise drops dependent upon cloud coverage and elevation. Any places with thick clouds and showers could experience max drops, with high valleys and upper elevations within the High Knob Massif being favored for some of the largest temperature drops.
Storm Prediction Center Severe Thunderstorm Potential To 8:00 AM Wednesday
The focus turns toward another heavy rainfall potential setting by later Tuesday into Wednesday along and ahead of a strong cold front. The Storm Prediction Center has also issued a marginal-slight risk for severe thunderstorms for a large region along and west of the Appalachians.
Rainfall Totals ( August 1-18 )
City of Norton: 7.39″
Big Cherry Lake Dam: 7.62″
Eagle Knob of High Knob Massif: 8.67″
Due to wet antecedent conditions, strong rises on streams and other high water problems will be possible if heavy rainfall develops late Tuesday into Wednesday.
An ALERT For Local Downpours Of Heavy Rainfall Continues Through Friday Afternoon
A high water content air mass will continue over the mountain area into Friday afternoon. Showers & downpours with heavy to locally excessive rainfall will remain possible before much drier air overspreads the Cumberland Mountains by Friday night into Saturday morning. A beautiful weekend is expected.
Overnight Into Friday Morning
Hazy & humid. Areas of dense fog ( widespread at highest elevations within orographic clouds ). Chance of showers & thunderstorms, especially toward morning. Downpours possible. SW-W winds 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges. Temperatures widespread in the 60s to lower 70s.
Friday Morning Into Friday Afternoon
Humid. Showers & thunderstorms likely. Local downpours. Low clouds with dense fog at highest elevations. Becoming partly cloudy and less humid by late afternoon into early evening. Winds shifting W-WNW at 5-10 mph, with higher gusts. Temperatures varying from upper 60s to lower 70s at highest elevations to the middle 70s to around 80 degrees. Warmer south into the Great Valley and Tri-Cities.
Friday Night Into Saturday Morning
Clearing and less humid ( especially in higher elevations ). Areas of dense valley fog. WNW-NW winds 5-10 mph and diminishing along all but highest ridges. Temperatures varying from lower 50s to the lower 60s ( coolest in high mountain valleys above 3000 feet ).
Saturday Afternoon
Partly sunny. Light SSW-WSW winds generally less than 10 mph. Temperatures varying from upper 60s to lower 70s at highest elevations to the upper 70s to lower 80s ( warmer south into the Great Valley and Tri-Cities ).
Saturday Night Into Sunday Morning
Mostly clear. Areas of dense valley fog. Light winds. Large vertical temperature spread developing between the cooler valleys and milder ridges. Temperatures varying from the upper 40s to lower 50s in coolest valleys to mid-upper 60s.
A more significant air mass change is being monitored for the final days of August, starting later next week, with potential for much less humid air and chilly nights. Stay tuned for updates.
Weather Discussion ( Jungle-like )
The mountain landscape during August 2017 has turned into a tropical, jungle-like state with very wet conditions featuring a daily array of downpours.
Month To Date National Weather Service and Estimated Rainfall Totals
*Automated Rain Gauge Totals ( August 1-17, 2017 )
Big Stony Creek: 8.27″
Dungannon: 7.98″
*Eagle Knob: 7.90″
*Robinson Knob: 7.21″
*Little Mountain: 7.10″
*Big Cherry Lake Dam: 7.04″
*Actual totals are greater, especially for rain gauge sites above 3000 feet in the High Knob Massif.
Month To Date National Weather Service and Estimated Rainfall Totals
Although coverage of heaviest rainfall amounts is greater than the above graphics indicate across southern Wise and northern Scott County, Va., they illustrate the general trend observed so far during August 2017.
NAM 12 KM Model Precipitable Water Forecast At 11:00 AM Friday – August 18
The current ( 11:45 PM Thursday ) presence of orographic clouds capping highest elevations within the High Knob Massif and Black Mountain, in advance of the approaching moisture plume ahead of a cold front, indicates that the potential for significant rainfall amounts must continue to be respected until drier air actually arrives later Friday afternoon-evening
Early morning to early afternoon is currently the period most favored for heavier rainfall with orographic enhancement.
Big Stony Creek of High Knob Massif – August 7 to August 18, 2017
Although dropping, stream levels remain high and swift on steep creeks draining the high country of the High Knob Massif. Please continue to use caution around these gushing whitewater creeks.
While humid, very moist air will continue to be felt into early Friday afternoon, a notable decrease in atmospheric moisture will occur by Friday evening into Saturday.
NAM 12 KM Model Precipitable Water Forecast At 8:00 PM Friday – August 18
The potential for a more significant air mass change, with an early autumn flavor, is being monitored for the final week of August ( the 5-10 day range at this point in time ).
European 51-Member Ensemble Mean 850 MB Temp Forecast: Days 6-10
ALERT For Local Downpours Of Heavy Rainfall Into At Least Friday – Caution Continues To Be Advised Along Creeks Draining The High Knob Massif
A high water content air mass will continue over the mountain area into at least Friday. Showers and downpours with heavy to locally excessive rainfall will remain possible.
Due to heavy rainfall Monday into early Tuesday, steep creeks draining the High Knob Massif continue to run very strong with ROARING water. Caution is advised around this swift water.
Overnight Into Monday Morning
Mostly cloudy. Humid & hazy. Areas of valley fog. Chance of a sprinkle or rain shower. Winds SSE to SSW winds 5-10 mph, with some higher gusts, along mid-upper elevation mountain ridges. Temperatures widespread in the 60s.
Monday Morning Through Monday Afternoon
Mostly cloudy. Humid. Chance of hit-miss showers and thunderstorms. Downpours possible. Light & variable winds outside any storms. Temperatures varying from upper 60s to low 70s in upper elevations to the middle to upper 70s ( warmer south into the Great Valley ). Areas of dense fog possible at highest elevations.
Monday Night Into Tuesday
Mostly cloudy. Humid & hazy. Areas of dense fog. Chance of a shower or thunderstorm. Winds SSW-WSW 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures in the 60s to near 70 degrees.
Tuesday Morning Through Tuesday Afternoon
A chance of showers & thunderstorms. Downpours possible. Winds SW-W at 5-10 mph along mid-upper elevation ridges. Temperatures varying from 60s in upper elevations to the middle-upper 70s ( warmer south into the Great Valley ).
Tuesday Night Into Wednesday Morning
A chance of showers & thunderstorms. Downpours possible. Winds SSW-WSW at mainly less than 10 mph along ridges. Temperatures varying from upper 50s to upper 60s. Areas of dense fog.
Wednesday Morning Through Wednesday Afternoon
A chance of showers & thunderstorms. Downpours possible. Light winds. Temperatures varying from upper 60s to low 70s in upper elevations to the upper 70s to lower 80s.
Wednesday Night Into Thursday Morning
A chance of showers & thunderstorms. Downpours possible. Winds SSW-WSW 5-10 mph, with higher gusts, along mid to upper elevation mountain ridges. Humid & hazy with areas of fog. Temperatures widespread in the 60s to lower 70s.
A stronger cold front and upper air trough is being monitored for later this week into race weekend at Bristol. The strength & south-ward progression of this feature will help determine conditions. Stay tuned for updates.
Weather Discussion ( Muggy Air )
Updated Discussion
A general 2.00″ to 3.00″ of rain fell across the High Knob Massif area into the day Tuesday ( August 15 ), with strong rises on creeks and local high water.
Big Stony Creek of High Knob Massif
Big Stony Creek crested 0.2 feet above flood stage in northern Scott County on Tuesday as run-off roared out of the high country. Both the Upper Norton Reservoir and the Big Cherry Lake are now overflowing their spillways.
A general 6.00″ to 8.00″ of rainfall has now been observed across southern Wise County and northern Scott County during the first half of August.
Saturated ground and the continuation of a high water content air mass increases the odds that downpours will cause additional, perhaps more significant, water problems in at least localized locations into Friday. I have posted an alert for everyone living and traveling across this water logged mountain terrain.
Stay tuned to NOAA weather radio and your favorite media sources for possibles advisories or warnings that may be needed during the next few days.
Previous Discussion
A muggy mass of air will continue to grip the mountain landscape through most of this week, with occasional showers and downpours being possible at times.
Thick Vegetation In Backwaters of Big Cherry Lake – August 13, 2017
A little less humid air was felt Sunday ( August 13 ) with MAX temperatures varying from upper 60s to upper 70s ( 79 degrees Clintwood and upper 60s on coolest northern slopes within the High Knob Massif ) in the Cumberland Mountains.
Towering Cumulus Over Powell Valley of the High Knob Massif
An abundance of clouds and low-level moisture will help to hold temperatures down, but muggy air will make it feel uncomfortable at most elevations.
NAM 12 KM Model Total Rainfall Forecast To 8 AM Thursday – August 17, 2017
Locally heavy rainfall will be possible, but models will also continue to struggle to pinpoint where that occurs well in advance of developing activity ( therefore, nowcasts or very short-term forecasts, based on Doppler radar, will remain most accurate during this type of pattern ).
GFS Model Total Rainfall Forecast To 8 PM Friday – August 18, 2017
A stronger cold front and upper air trough will be approaching the mountain region by later this week into the upcoming weekend. The speed, strength and south-ward progress of this feature will be key to conditions experienced during race week-weekend ( and perhaps during the eclipse on August 21 ).
***ALERT For Heavy Rainfall Development Overnight Into Monday With Potential For Water Problems
A strong SW low-level jet will enhance orographic forcing overnight into Monday in advance of an approaching storm system. Heavy to locally excessive rainfall will be possible, especially within the most favored lifting zones centered upon the High Knob Massif & Black Mountains-Tennessee Valley Divide. Those living and driving along streams and within typically flood prone & poor drainage areas should remain alert for the potential of rapid water level rises.
Former Alerts
The Storm Prediction Center Has Issued A Marginal Risk Of Severe Thunderstorm Development During Friday Afternoon-Evening
Friday Afternoon
Showers & downpours in thunderstorms developing. Some storms could be strong to locally severe. SSW-WSW Winds 10-20 mph, with higher gusts, along mid-upper elevation mountain ridges-plateaus. Temperatures varying from 60s in upper elevations to the mid-upper 70s ( warmer south into the Great Valley ).
Friday Night Into Saturday Morning
A chance of hit-miss evening showers-thunderstorms then becoming partly to mostly clear overnight. Areas of fog. Winds shifting NW-N at 5-15 mph. Turning cooler. Temps varying from the mid-upper 40s to the upper 50s ( coolest within upper elevations ).
Saturday Afternoon
Partly to mostly sunny. Blue skies. Pleasant. Light NW-N winds. Temperatures varying from 60s in upper elevations to the low-middle 70s.
Saturday Night Into Sunday Morning
Clear evening skies, then increasing high clouds overnight into morning. Light winds, then becoming SE-S along high mountain ridges and increasing toward morning. Large vertical temperature spread between colder valleys and milder ridges. Temperatures varying from 40s in colder mountain valleys to the upper 50s to lower 60s ridges.
Sunday Afternoon
Partly-mostly cloudy. More humid. Chance of a localized shower or thunderstorm. Light winds, except breezy-gusty on high mountain ridges from the SSW-SW by late. Temps varying from upper 60s to lower 70s in upper elevations to the upper 70s to lower 80s.
Sunday Night Into Monday Morning
Cloudy. Becoming windy across the higher elevations. Showers & downpours in thunderstorms developing. Heavy rainfall totals possible. SSE to SSW winds increasing to 10-20 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet. Winds SSW-WSW 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures varying from the upper 50s to mid-upper 60s. Dense fog developing across upper elevations.
Monday Morning Into The Afternoon
Showers & downpours in thunderstorms. Heavy rainfall totals possible. SW winds 10-20 mph, with higher gusts, across mountain ridges-plateaus. Temperatures in the 60s to lower-mid 70s ( coolest at highest elevations ). Dense fog across upper elevations.
A wet and occasionally stormy pattern is expected this week with below average temperatures for August. More heavy rainfall may become possible by later in the week. Stay tuned for updates.
Weather Discussion ( Changeable )
A beautiful weekend featuring chilly night-time temps, with 43 to 49 degrees in cooler mountain valleys, will now give way to a return of deep moisture driven by a low-level jet of strong SW winds overnight into Monday ( Aug 7 ).
NAM 12 KM Model Total Rainfall Forecast Next 60-Hours ( Sunday AM Run )
Although models vary from run to run on precise amounts for any given location, the general trend is clear when also including the European Ensemble Group ( 51-Members ) that a heavy rainfall setting is emerging for the mountain area.
NAM 12 KM Model Total Rainfall Forecast Next 60-Hours ( Sunday PM Run )
Past climatology of many such events, featuring a SW low-level jet, favors heaviest rain amounts being focused upon the High Knob Massif-Landform & Tennessee Valley Divide corridor, and locations along and generally west of the Tennessee-North Carolina border.
Stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warnings that may be needed through Monday.
Previous Discussion
Another cold front with showers and downpours in thunderstorms during Friday will give way to another pleasant weekend in the mountains.
High Knob Massif Webcam – University Of Virginia College At Wise
A general wet pattern is looking to develop next week into mid-August, but exact amounts for any location remain in question and must be updated in coming days.
GFS Model 2 AM Run Friday – Forecast Rainfall Next 10 Days
While the numbers will vary for any given place, the mean of ensembles, such as the favored European Model group, is suggesting that a wet pattern will rule the landscape.
GFS Model 8 AM Run Friday – Forecast Rainfall Next 10 Days
The other main theme will be a continuation of below average temperatures across much of the continental USA, outside of the Pacific Northwest, for late summer.
European Ensemble MEAN 850 MB Temp Anomalies: Days 1-5
Near to above average temperatures are also expected across Florida, but nothing like the heat ( relative ) at higher latitudes across North America.
European Ensemble MEAN 850 MB Temp Anomalies: Days 6-10
It has been a relatively cool summer in the high country of the High Knob Massif, as illustrated by High Knob Lake.
High Knob Lake of High Knob Massif – August 1, 2017
High Knob Lake June-July 2017 Temperatures Average Daily MAX: 71.2 degrees Average Daily MIN: 55.6 degrees June-July MEAN: 63.4 degrees Highest Temperature: 80 degrees Lowest Temperature: 44 degrees
Even cooler temperatures, especially at night, have been recorded within the Big Cherry Lake Basin where average nightly low temperatures have been as chilly as 51 degrees for the combined June-July period ( the lowest summer MIN reaching 38 degrees on June 28 ).
The coolest day-time temperatures have occurred at highest elevations, with 68.4 degrees being recorded on Eagle Knob for the average June-July maximum ( highest summer temp reaching 77 degrees on July 22 ).
