*A chilly air mass will be felt through the next several days, with shocking temperatures ( especially when factoring in wind chills at higher elevations ) in comparison to the mean of recent months.
*Unsettled conditions will occur as the remnants of Michael race away into the Atlantic and a secondary cold front drops into the mountains Friday Night into early Saturday. The first pellets of sleet or flurries & light rime will be possible at highest elevations, with a chance of a few cold rain showers in other locations.
*The first temperatures at freezing will occur at highest elevations, with the first sub-freezing wind chills at upper elevations on both Friday & Saturday mornings. Runners in the Cloudsplitter 100 Race will need to be prepared for these conditions.
*A southerly flow redevelops during the second half of the weekend, with warm air advection and increasing clouds. Wind chills will continue to be a factor in the upper elevations ( especially along high ridges ).
Thursday Night Into Friday Morning
Mostly cloudy. Turning much colder. Low clouds-fog with a chance of drizzle or light riming (highest peaks). NW winds 5-15 mph with some higher gusts. Temperatures dropping into the 30s to lower 40s ( around 30 degrees at on highest peaks ). Wind chills dropping into the 20s and 30s ( coldest at highest elevations ).
Friday Morning Through The Afternoon
Becoming partly to mostly sunny ( blue skies ), then increasing high clouds by late. Light to occasionally breezy W-NW winds. Seasonably chilly with temperatures varying from upper 40s to lower 50s at upper elevations to the mid 50s to lower 60s. Wind chills in the 30s to lower 40s at the highest elevations.
Friday Night Into Saturday Morning
Becoming cloudy. Chance of rain showers. Flurries or sleet pellets possible at highest elevations. Winds WNW-NW 5-15 mph, with some higher gusts. Temperatures dropping into the 30s to lower 40s ( around 30 degrees on highest peaks ). Wind chills dropping into the 20s and 30s, except upper 10s to lower 20s on highest peaks.
Saturday Morning Through The Afternoon
Low clouds giving way to partly cloudy skies. Chilly. Light northerly winds. Temperatures varying from upper 30s to lower 40s at upper elevations to the upper 40s to low 50s.
Saturday Night Into Sunday Morning
Mostly cloudy. Becoming gusty along mountain ridges. Winds SSE to S at 5-15 mph, with some higher gusts, on mountains ridges below 2700 feet. Winds S-SW at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures mainly in the 40s. Wind chills in the 30s to lower 40s ( coldest at upper elevations ).
Be sure to check out What Makes High Knob Special, the latest published series by Wally Smith and Wayne Browning which talks just a little bit about this great mountain mass (scroll down to article links).
Weather Discussion ( Chilly Air )
Friday Morning Update
A low cloud deck held through the night with dense fog and low clouds continuing to engulf highest elevations this AM.
High Knob Massif Webcam – University Of Virginia’s College At Wise
It is a wintry morning up top with 34 degrees and wind chills in the 20s, amid dense fog-low clouds. This is what conditions will be like into Saturday morning, only even more nasty for the 8:00 AM start of the Cloudsplitter 100.
Previous Discussion
Falling temperatures through Thursday afternoon are just the beginning of a chilly period of weather conditions as Autumn 2018 finally decides to arrive.
High Knob Massif Webcam – University Of Virginia’s College At Wise
As of late afternoon Thursday air temperatures had fallen into the 40s, and wind chills into the 30s, at the summit level of High Knob to mark the beginning of a chilly to cold period of conditions amid the high country. A radical change, indeed, for runners taking part in the Cloudsplitter 100 race through this weekend.
Thursday afternoon breaks in the overcast will close back up as northwest flow and cold air advection drop air temps significantly into Friday morning. Clouds bases engulfing the summit of High Knob will lower to cover more of the high country into the upcoming night ( the first light riming may occur toward Friday morning on peaks ).
Clouds will break and Friday skies will feature a classic autumn look, with cumulus hung amid deep, blueness.
Conditions then begin changing Friday night into early Saturday as low-level moisture increases again and cloud bases drop back over the high country. Although most places will have a chance of showers, the first frozen precipitation types will be possible at high elevations during the predawn to post-sunrise period Saturday.
*The first light accumulation, or dusting, of snow will be possible farther northeast in the northern mountains of West Virginia at the highest elevations. A sign of the season upcoming.
Sunshine returns Saturday, eventually, and then more changes occur as moisture begins streaming across the USA from remnants of Sergio ( moving from the eastern Pacific into the southwestern USA ).
The Bottom Line, a much cooler but changeable period of weather is expected through this weekend.
Unseasonably mild conditions will return to dominate the next 1-2 weeks, with another trend toward above average precipitation developing as well during this extended 5-10+ day range ( remember that October is climatologically the driest month of the year ).
The anomalous warmth of September is exemplified by a 68.5 degree average daily maximum on Eagle Knob of the High Knob Massif, which just beat the 68.4 degree average daily max observed during August!
How often are average September high temperatures warmer than August? A question to be researched, but a quick look through the Wise database from 1955 to 2012 reveals NONE. NADA. No year had a September with warmer mean highs than August!
Signs of a major pattern change are beginning to show up in the far extended range, by mid-late October into November as a late developing, central-Pacific based El Nino ( +ENSO ) continues to form and exerts more influence upon the synoptic-scale flow fields across the Northern Hemispere ( along with other factors ).
Overnight Into Monday Morning
Partly cloudy then increasing clouds toward morning. Areas of dense valley fog. Winds S-SW at 5-10 mph with higher gusts on mid-upper elevation mountain ridges. Temps varying from lower 50s to the low 60s ( coolest in mountain valleys at upper elevations ).
Monday Afternoon
Partly-mostly cloudy. Chance of hit-miss showers and thunderstorms. Light SSW to SW winds generally less than 10 mph. Temperatures varying from mid-upper 60s to the mid-upper 70s ( coolest in upper elevations ).
Monday Night Into Tuesday Morning
Mostly cloudy. Chance of a shower. SW-W winds 5-10 mph with some higher gusts on mid-upper elevation mountain ridges. Temperatures in the upper 50s to middle 60s. Areas of valley fog.
Tuesday Morning Through The Afternoon
Chance of showers & thunderstorms. SW-W winds 5-15 mph, with some higher gusts on mountain ridges. Temps varying from the 60s to the middle 70s ( coolest in upper elevations ).
Tuesday Night Into Wednesday Morning
Partly-mostly cloudy. Chance of a shower. Areas of dense fog. Winds WSW-WNW at 5-10 mph on mid-upper elevation mountain ridges. Temperatures varying from the middle 50s to the middle 60s.
Reference the High Knob Hellbender 10K section for a forecast specifically designed for this race in coming days ( my Cloudspitter 100 forecast will be featured during coming weeks in advance of this race ).
Weather Discussion ( More Of Same )
A brief cooling trend which came just in time for the 12th Annual High Knob Naturalist Rally will become a memory through coming days.
High Knob Lake Recreation Area – High Knob Naturalist Rally 2018
A buoy line can be seen across the lake in the far distance to keep kayaks and canoes safely away from the overflowing High Knob Lake Dam. Up to 3.50″ of rain were reported in the area immediately prior to the Naturalist Rally.
Temperatures in the 50s to lower 60s were observed during the time of this year’s High Knob Naturalist Rally ( 7:00 AM to 5:30 PM below ), with morning low clouds and fog slowly giving way to some welcomed afternoon sunshine.
Eagle Knob of High Knob Massif ( Time UTC )
Temperatures in the 50s during much of the rally were in rather dramatic contrast to 70s-lower 80s in the Tri-Cities, with some visitors seen shivering ( and talking about the chill ).
Beautiful Water Flowing Into High Knob Lake – 2018 Naturalist Rally
Mean averages during the next week to 10 days will be lower given decreasing sun angles, but nothing close to reality for this point in the year ( see graphics below ).
Approaching Sunset – Upper Norton Reservoir – September 29, 2018
While trees are changing again in spurts, the combination of atypical mildness + a lack of frost + anthracnose fungi impacts are making it slower and duller so far. The final result yet to be determined; however, clearly these ingredients are far from ideal and have already caused some significant leaf drop ( especially at the higher elevations above 3500 feet ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
A deepening western USA upper trough will turn flow more S-SW across the eastern USA over time, renewing the above average precipitation pattern.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
While some signs of a major change are beginning to show up in the far extended range, the next 1-2 weeks are looking anomalously mild at this present time.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5
Warm anomalies in the 6-10 day range ( below ) increase due to both a combination of deeper southerly flow from the tropics and to climatology, given temperatures should be declining ( in the mean ) moving through October.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 6-10
This could be setting the region up for a HUGE temperature crash once a change finally occurs, and this pattern flips from current upper air ridging into upper troughing.
An ALERT for redevelopment of low clouds and dense fog overnight through Saturday Morning.
Abundant low-level moisture will support dense fog formation, and low clouds, through the overnight into Saturday morning. Caution is advised for travelers.
Former ALERT
ALERT Continues For High Water Levels On Creeks Draining The High Knob Massif Into Friday Afternoon
As of 9:00 AM ( September 28 ) Big Stony Creek was dropping from an overnight crest of around flood stage, with a continuation of ROARING water levels.
Significant overflow had developed at Big Cherry Dam with ROARING water levels on South Fork of Powell River ( which remained below flood stage ).
Caution is advised along & downstream of these steep creeks for swift water and slick banks, this includes Little Stony Creek and numerous others along the Wise-Scott border area, through Friday.
Big Stony Creek of High Knob Massif
At 9:00 PM Thursday creeks were near flood stage, with around 3.00″ of total rainfall during this event at upper elevations in the High Knob Massif. Caution Is Advised in locations along and downstream of these roaring creeks.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Wednesday Night Into Thursday Morning
Humid with a chance of rain showers. Thunder possible. Low cloud bases with areas of fog, dense at times, especially above 2500 to 3000 feet. Winds NW to NE at 5-10 mph, with some higher gusts. Temperatures dropping into the upper 50s to middle 60s.
Thursday Morning Through The Afternoon
Cloudy with periods of rain. Thunder also possible. Local downpours. Variable winds at generally less than 10 mph. Temperatures from around 60 degrees ( highest elevations ) to mid 60s to 70 degrees. Low cloud bases. Areas of fog, dense at upper elevations.
Thursday Night Into Friday Morning
Showers. A chance of thunder. Downpours possible, especially during the evening. Winds WNW-N at 5-15 mph, with higher gusts. Areas of fog, widespread and dense at upper elevations. Temperatures falling through the 50s, with 50-55 degrees at high elevations.
Friday Morning Through The Afternoon
A chance of drizzle or local showers. Partly-mostly cloudy. Winds NW to NE at mainly less than 10 mph. Temperatures varying from upper 50s to the upper 60s.
Friday Night Into Saturday Morning
Chance of drizzle, low clouds and fog redeveloping, dense and widespread fog above 2500-3000 feet. NW-N winds at generally less than 10 mph. Temperatures in the 50s, with upper 40s to low 50s in cooler mountain valleys.
Saturday Morning Through The Afternoon
Low clouds with areas of dense fog and possible drizzle through the morning. Rising cloud bases with breaks by mid-late afternoon. Light NNE-ENE winds. Temperatures in the mid-upper 50s to mid-upper 60s.
High Knob Naturalist Rally ( Sept 29 )
Looking Across High Knob Lake Basin – September 22, 2018
High Knob Naturalist Rally Forecast
Dense fog and low clouds over saturated ground is expected to be present through the morning, followed by rising cloud bases with breaks to partly cloudy skies during the afternoon.
Conditions will remain cool on light NNE-ENE winds. Temperatures will mainly be in the 50s at High Knob Lake ( be sure to dress for chilly conditions ) and may rise above 60 degrees if sunshine becomes abundant.
Friday – September 28 Temperatures at High Knob Lake
*University Of Virginia’s College At Wise Research Station National Weather Service calibrated temperature sensor ( Data Period: November 19, 2016 to Present )
*The average daily maximum during September 1-22 was nearly as warm as observed during July ( 73.7 degrees ), much above average for this time of year, and was warmer than the average summer maximum at High Knob Lake in 2018 ( 72.4 degrees ). The highest summer temperature reached 80.9 degrees ( 150 total minutes at or above 80 degrees during 2018 at High Knob Lake ).
A seemingly endless summer weather pattern is expected to continue through this week, and perhaps through the first week of October, per the latest trend of the European 51-member ensemble mean. The only exception being a brief period with notably cooler air this weekend, just in time for the Naturalist Rally!
Some of the coolest air will be Saturday into early Sunday as northerly upslope flow helps to bring a touch of autumn to the high country just in time for the Naturalist Rally.
Unfortunately, for those looking for true autumnal chill that will last it is just not in the cards. Not yet.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
The only change in the short-term is a small drop in heights and minor weakening of the upper ridging before it builds back again.
The latest trend in the 6-10 day ( below ) is to maintain anomalous upper air ridging over the eastern USA to keep temperatures running well above average.
Note that significant chill at this time of year would be that which features mountain valley frost and freezes, especially in the high country. While air will cool some in upcoming days it will not be anything like typical for this time of year and may not be able to equal what has already been observed in August ( frost occurred during August 24 in Alder Swamp of Dolly Sods, Wv., where the lower dewpoint air was able to do its thing with drainage ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
This type of upper air pattern equates to much above average warmth for this time of year, with any cooler air in coming days being short-lived as a boundary stalls and lifts back northward once again.
European Model 850 MB Temperature Anomalies Forecast: Days 1-5
While most of Alaska has shifted back to unseasonable warmth ( above ), the bulk of Canada has turned chilly.
Significant changes are being noted in the 6-10 day range ( below ), with cold air building and pooling along the eastern side of the northern Rockies ( but with weaker anomalies than forecast a week ago ).
European Model 850 MB Temperature Anomalies Forecast: Days 6-10
This latest trend will shear away cold air building along the eastern side of the northern Rockies as it slides southeast into a rebounding upper air ridge.
Eventually, chilly air in Canada will be able to spread southeast but perhaps not until the second week of October? Stay tuned for updates.
Wetness Continues
High Knob Lake on September 22, 2018
*Cloud bases were engulfing highest ridges at the time this view was captured, with bases soon dropping to also engulf High Knob Lake Basin where every September day has featured RH-Dewpoints which have reached saturation. A trend observed during much of this growing season and likely responsible, at least in part, for Anthracnose fungal infections impacting many tree species at upper elevations ( especially maples and northern red oaks ).
Continued warmth will also support an above average rainfall trend, with showers & downpours in thunder-storms increasing in coverage. Again, the potential for locally heavy to excessive rainfall will need to be monitored through upcoming days.
Although heaviest rains with Florence remained to the east, September has been another wet month with 22 of the past 24 days featuring measurable rain in the official rain gauge at the City of Norton Water Plant.
This boosted 2018 precipitation to 55.59″ ( M ) with a general 59.00″ to 66.00″+ in upper elevations across the high country of the High Knob Massif.
( M ) = Missing moisture during February with a rain gauge spill.
Recap of Florence Rainfall Totals
A general 1.00″ to 3.00″ fell along the Cumberland Mountains, with much heavier amounts to the east and southeast ( as expected ).
Mount Mitchell SP: 14.32″
Meadows of Dan 5 SW: 7.99″
Whitetop Mountain: 7.08″
Boone NWS Cooperative: 6.22″
Grayson Highlands SP: 5.70″
NWS Precipitation Analysis During September 14-21
Although rainfall totals came in within or very close to the ranges on my forecast graphic they were held down somewhat by a more northerly turn of the low center, which tracked east of the official NHC track and model mean. This especially impacted the south-western portions of the mountain chain, where only 1.44″ were measured at Newfound Gap and 3.10″ on Mount LeConte ( atop the Great Smokies ). That was the big error on my graphic, with the 14.32″ not far away on Mitchell being on target ( illustrating how minor track changes can create a huge difference ).
Compare the NHC Official Forecast Track:
National Hurricane Center Official Forecast Track For Florence
To the Actual Inland Path followed by Florence:
Actual Florence Track Plotted On Google Earth
The Great Smokies and most of the High Knob Massif were to the left ( west ) of the track center. Heaviest rains fell mainly east of the track line. This created huge rainfall differences ( 11.22″ ) between Mitchell and Mount LeConte ( 14.32″ versus 3.10″ ).
*Weather stations on Mount Mitchell ( 6240 feet ) and Mount LeConte (6400 feet ) are only different by 160 vertical feet.
They are radically different; however, with respect to air flow trajectories and mean prevailing winds in terms of orographic forcing. The track difference with Florence illustrated this.
*A general 2″ to 4″ of rainfall is currently expected across much of the Cumberland Mountains. Greater totals will also be possible at upper elevations. Strong water levels rises will occur and flooding can not be ruled out should totals end up near, or above, the higher end of this forecast range.
Rainfall Totals During September 15-18 Period
*Flooding rainfall amounts are expected along and east of the Blue Ridge province, with widespread totals of 4″ to 10″ . Locally heavier amounts, with potential for up to 18″+ will be possible at higher elevations along the Blue Ridge ( e.g., Grandfather Mountain and Mount Mitchell ).
Lesser 1″ to 4″ rainfall amounts are expected across adjacent zones, with locally higher amounts possible at upper elevations in the Cumberland Mountains.
A chance of showers & thunderstorms Saturday will give way to increasing wind-rain into overnight hours of Saturday-Sunday as the remnants of Florence begin impacting the Mountain Empire.
Florence is currently beneath a weak wind field, but is expected to begin moving fasting in coming days. This motion will be critical to rain amounts as noted below.
Orographic forcing will be a factor with enhanced rain amounts on windward slopes-crests. The current forecast track will generate inflow changes over time, complicating the rainfall forecast over mountainous locations within the Mountain Empire.
*NOTE that eventual rain amounts will be dependent upon the speed of movement of these remnants, with slower movement generating heavier amounts than forecast and an acceleration resulting in lesser amounts than currently forecast.
Stay tuned to NOAA Weather Radio and your favorite media sources for updates on Watches and Warnings which will be issued during this evening.
The main concern for the mountains is how far inland will the remnants of Florence get + how fast will they move. The National Hurricane Center has been going with the European Model which has been, by far, the most consistent with the track.
Main jet stream cores are far to the north, and while there is some SW flow over the area now that is likely to weaken with large-scale subsidence in advance of Florence by later this week.
GOES-16 Water Vapor Image – Evening of September 10, 2018
While I think it will be Wednesday into Thursday before confidence on the inland track and speed increases by a significant amount, it is possible to discuss some of the possibilities ( for planning ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
The 51-Member European Ensemble Mean ( above ) shows Florence moving beneath a 500 MB upper air ridge axis during the next 5 days, which has been responsible for recent intensification.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 4-8
The 4-8 day period, during September 14-18 above, keeps the main jet stream cores far to the north and a large, elongated upper ridge over the eastern USA.
The break or weakness in the ridge ( above ) shows where the remnants of Florence are likely to be.
Worst And Best Case Scenarios For The Cumberland Mountain Range
It appears nearly certain that Florence will turn into a disaster, perhaps a Mega-Disaster, for portions of the middle Atlantic. Historical odds would favor locations along and east of the Blue Ridge for worst conditions.
With the above noted, at this point in time, major flooding can not yet be ruled out for the Cumberland Mountains and surrounding Mountain Empire.
*While the European Model has been most consistent, individual runs and ensemble members have been widely varied on MAX rainfall amounts with up to 48.00″ ( 4 Feet ) in the worst case scenario being predicted for portions of Virginia and North Carolina along and east of the Blue Ridge. Anything remotely close to that would generate historic, deadly flooding ( of course, anyone knows that ).
Individual runs of the operational European, as well as its ensemble members, can be expected to continue to vary on rainfall amounts during the next couple of days despite a rather consistent trend of bringing a major hurricane into the Atlantic coast. A problem is with weak winds aloft the remnants will begin to slow down once it loses forward momentum and begins to feel frictional drag of the land.
Here I will briefly outline what would be the best and worst case scenarios for the Cumberland Mountains, where this website is mainly focused upon.
Best Case Scenario
The best case scenario to watch for would be that the remnants turn north following landfall and remain far to the east, keeping the Cumberland Mountains and Mountain Empire amid the subsidence zone of sinking air around the periphery of the core.
With a system like this one must begin to talk about orographic forcing, such that the best case setting for the Cumberland Mountains with the remnants moving far inland would be for them to move toward northern Georgia, southwestern North Carolina to maintain a southeasterly flow into southwestern Virginia and eastern Tennessee. This scenario, of course, would be the worst case for western North Carolina.
Worst Case Scenario
The worst case scenario to watch for would be for the remnant core to move toward northern North Carolina and southwestern Virginia, east of the Cumberlands, with a wrap-around northerly upslope flow generated into the local mountans with a stalling system. The orographics would then favor excessive rainfall over the local mountains and near the core of the remnant low ( especially on enhanced nocturnal convergence ).
There are many other possible scenarios, of course, but these are just ones mainly focused upon the Cumberland Mountains ( and based upon past climatology ).
*Above average temperatures will tend to dominate much of this work week within a hazy, maritime tropical ( mT ) air mass. Showers & thunderstorms, with hit-miss downpours, will be possible ( especially mid-morning to early evening ).
Due to weak winds aloft any shower or thunderstorm will be slow moving and capable of dropping heavy rainfall over local areas.
*The coverage of showers & thunderstorms will increase later this weekend into the Labor Day Holiday period, with downpours. Temperatures will tend to slightly decline due to an increase in cloudiness and showers-thunderstorms.
*An above average temperature trend is currently expected to continue through the first week of September.
Overnight Into Monday Morning
Partly cloudy to mostly clear. Areas of fog. Light S-SW winds generally less than 10 mph on mid-upper elevation mountain ridges. Temperatures varying from mid-upper 50s in valleys at upper elevations to the low-middle 60s.
Monday Morning Through The Afternoon
Partly cloudy. Chance of hit-miss showers-thunderstorms. A local downpour possible. Light & variable winds. Temps varying from low-mid 70s to the low-mid 80s ( coolest at upper elevations above 3000 feet ).
Monday Night Into Tuesday Morning
Partly to mostly clear. Small chance of a shower or storm. Light and variable winds becoming SSW-WSW at 5-10 mph, with higher gusts, mid-upper elevation mountain ridges. Areas of fog. Temperatures varying from upper 50s to lower 60s in cooler valleys to middle-upper 60s.
Tuesday Morning Through The Afternoon
Partly cloudy. Chance of hit-miss showers-thunderstorms. Local downpours possible. Winds S-SW generally less than 10 mph outside any storms. Temperatures varying from the lower-middle 70s to the lower-middle 80s.
Tuesday Night Into Wednesday Morning
Partly to mostly clear. Small chance of a shower or storm. Light and variable winds becoming S-SW at 5-10 mph, with higher gusts, mid-upper elevation mountain ridges. Areas of fog. Temperatures varying from mid-upper 50s to lower 60s in cooler valleys to the middle-upper 60s.
Wednesday Morning Through The Afternoon
Partly cloudy. A chance of hit-miss, slow moving showers and thunderstorms. Downpours likely in any activity. Light SSW-SW winds generally less than 10 mph. Temperatures varying from low 70s to the lower 80s ( warmer south into river valleys of the Clinch, Powell, and Holston ).
Wednesday Night Into Thursday Morning
Variable clouds. Chance of a shower or thunderstorms. Downpours possible. Areas of fog. Winds SW-W at 5-10 mph, with some higher gusts, on mid-upper elevation mountain ridges. Temperatures mainly in the 60s.
Weather Discussion ( More Summer )
A late summer weather pattern will return to dominate conditions through the Labor Day Holiday. This comes in wake of pleasant conditions in recent days.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Minimum temperatures fell into the 40s in cooler mountain valleys at upper elevations during August 23-25 ( low-mid 40s in coldest locations ).
High Knob Massif Mesonet *Big Cherry Lake Valley 2 June 1-August 25, 2018 Avg. Daily MAX: 70.9 degrees Avg. Daily MIN: 57.6 degrees Summer MEAN: 64.2 degrees Highest Temperature: 79 Lowest Temperature: 46
*MAX temperatures were somewhat higher and MIN temperature were somewhat lower within open portions of the Big Cherry Wetland Valley. Temps are all National Weather Service calibrated and very accurate.
High Knob Massif Webcam-University Of Virginia’s College At Wise
A notable increase in haze, with some orographic clouds, was observed developing Sunday as a continental Polar air mass gave way to advection of maritime tropical air.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5
Above average temperatures during the next 5 days, on average, will be supported aloft by mean upper air ridging across the southern and eastern USA.
European 51-Member Mean 500 MB Height Anomalies: Days 1-5
This basic pattern is expected to continue through the next 10 days, which includes the Labor Day Holiday period.
European 51-Member Mean 500 MB Height Anomalies: Days 6-10
*Showers & downpours in thunderstorms will continue at times, amid a humid air mass, into Tuesday Night.
Heavy to locally excessive rain amounts will remain possible in advance of a strong autumn-like cold front expected to arrive by late Tuesday.
NOAA’s Storm Prediction Center has issued a marginal risk of severe thunderstorm development along and in advance of this cold front.
*Cloud bases will lower and the air will turn notably cooler on northerly winds through Wednesday, with lingering showers possible in advance of a secondary dewpoint boundary that ushers in an early autumn-like air mass late Wednesday into Thursday.
An early autumn-like air mass will drop temperatures into the 40s to middle 50s within locations along & north of the High Knob Massif-Tennessee Valley Divide by Thursday AM. Even cooler air may be felt in colder mountain valleys by Friday morning ( August 24 ). Stay tuned for updates.
*The cooler, drier break will be temporary with a return of humid air and a trend toward above average temperatures by next weekend into the final days of August 2018.
Overnight Into Monday Morning
Partly-mostly cloudy. Muggy. Areas of dense fog. A chance of showers & thunderstorms. Locally downpours possible. Light SSE-SSW winds. Temperatures in the 60s to low 70s.
Monday Morning Through The Afternoon
Muggy & warm with a chance of showers & downpours in thunderstorms. Locally heavy rain possible. Light S-SW winds. Temperatures varying from upper 60s-low 70s in upper elevations to the upper 70s to lower 80s ( warmer south into the Great Valley ).
Monday Night Into Tuesday Morning
Mostly cloudy. Becoming breezy to windy. Chance of showers & thunderstorms. Local downpours possible. Winds S-SSW 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. Muggy with temperatures in the 60s to lower 70s.
Tuesday Morning Through The Afternoon
Showers & thunderstorms becoming likely. A few storms could be strong to severe. Local downpours. SW winds 5-15 mph, with higher gusts. Temperatures varying from upper 60s to the upper 70s.
Tuesday Evening Into Wednesday Morning
Showers & thunderstorms likely into the evening, then a chance of showers. A few storms could be strong-severe early with downpours. SW winds shifting W-WNW at 5-15 mph, with higher gusts into morning. Temps falling into the upper 50s to middle 60s.
Wednesday Morning Through The Afternoon
Mostly cloudy with a chance of showers. Low cloud bases at upper elevations, with dense fog into mid-morning to early afternoon at high elevations. Winds NW at 5-15 mph with some higher gusts. Temperatures varying from lower 60s to the low-mid 70s ( warmer south into the Great Valley ).
Wednesday Night Into Thursday Morning
Partly-mostly cloudy early, then decreasing clouds with areas of fog. NW-NE winds diminishing to 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures dropping into the 40s to middle 50s.
Thursday Afternoon
Sunny. Very pleasant. Blue skies. Light N-NE winds. Temperatures varying from lower-middle 60s in upper elevations to the lower 70s.
Thursday Night Into Friday Morning
Clear and unseasonably cool with a large vertical temp spread developing between the colder valleys and milder mountain ridges-exposed plateaus. Winds becoming SE to SSE at 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures varying from upper 30s to lower 40s in colder valleys at upper elevations to the mid 40s to low-mid 50s ( mildest on middle elevation ridges ). Areas of dense river valley fog.
Weather Discussion ( Changes )
With the 12th Annual High Knob Naturalist Rally now just over 1 month away, it is time for a nip to be felt amid air of the high country. Yeah, to less humid air!
September 29, 2018 at High Knob Lake Recreation Area
Featuring the most mountain-top lakes of any mountain in the southern-central Appalachians, this year’s 12th Annual Naturalist Rally will be held at 3500+ feet above mean sea level where the air is always cooler in the high country.
USDA Forest Service – High Knob Lake Recreation Area – Summer 2018
Meanwhile, the relentless stretch of muggy air continues for a little while longer until the first autumn-like cold front ushers in a temporary break by mid-late week.
High Knob Massif Webcam – University Of Virginia’s College At Wise
A refreshing and much cooler air mass will temporarily bring a dramatic change to the mountain area during the August 22-23 period into Friday AM of August 24.
European Model 850 MB Temp Forecast At 8 AM August 23, 2018
The middle range trend will be for humid air and above average temperatures to return during the final days of August 2018.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
NOTE: The 5.24″ of rain measured in Clintwood during August 1-19 pushed the annual total to 46.03″ ( 14.45″ above the 1981 to 2010 average for this point in a year ). The January 1-August 19 total being near the long-term annual average for Clintwood.
NWS Precipitation Analysis – Percent of Normal – During Past 90-Days
*Although a general 47.00″ to 57.00″ of precipitation have fallen in the City of Norton-High Knob Massif area so far this year, the actual annual departure is generally only near to a little above average. This is due to hit-miss summer thunderstorms and local wet feedbacks, superimposed upon the larger-scale weather pattern, which have allowed certain sites and corridors ( e.g., northern Virginia into Pennsylvania ) to receive above to much above average summer rainfall across the eastern USA ( versus nearby locations with near average summer rains ).
ALERT For The Potential Of Localized Flash Flooding Into This Weekend With Slow Moving Thunderstorms
Torrential downpours in slow moving thunderstorms have dropped heavy rainfall amounts across Dickenson County & northern portions of Wise County as of 1:30 AM Saturday, with potential for additional development of this nocturnal activity. Folks living along streams and in low-lying, flood prone locations should remain alert through this weekend.
*A moist, humid air mass will remain in place through this weekend with the potential for heavy to excessive rain amounts within localized places.
*The heavy rainfall threat is being enhanced by weak winds aloft beneath another anomalous, for this time of year, upper-level low with slow moving activity.
*A cold front will slowly work south and attempt to cross the mountains later in this weekend-early next week. The threat for heavy-excessive rain amounts will continue until somewhat cooler, drier air is transported south behind this boundary.
The Storm Prediction Center has expanded a marginal risk of severe thunderstorm development southwest to now include all of the mountain area through Wednesday
Storm Prediction Center Risk Regions
*A humid air mass will rule the mountain landscape through the upcoming week with chances of hit or miss showers & thunderstorms during early week.
*Another upper air trough will be developing over the eastern USA with increasing chances of showers and thunderstorms by later this week into the upcoming weekend ( August 8-12 period ).
*Near to above average temperatures during early-mid week will tend to cool with increasing showers and thunderstorms by later in the week-weekend.
Overnight Into Monday Morning
Partly-mostly cloudy. Chance of a localized shower. Areas of valley fog. SW winds 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures in the 60s to near 70 degrees.
Monday Morning Through The Afternoon
Mostly cloudy. Chance of showers & thunderstorms. Local downpours. Winds S-SW generally less than 10 mph outside of hit or miss showers-storms. Temperatures varying from lower-mid 70s to the upper 70s to lower 80s ( warmer south into the Great Valley ).
Monday Night Into Tuesday Morning
Partly to mostly cloudy. Chance of a shower or storm, especially during the evening. Areas of fog. Winds SSW-W at 5-15 mph with some higher gusts on mid-upper elevation mountain ridges. Temperatures widespread in the 60s.
Tuesday Afternoon
Partly to mostly cloudy with a chance of hit-miss showers and thunderstorms. Local downpours. Winds SW-W at 5-10 mph. Temperatures varying from the low-mid 70s in upper elevations to the low-mid 80s.
Tuesday Night Into Wednesday Morning
Partly to mostly cloudy. Areas of fog. Chance of a localized shower-thunderstorm. Winds SSW-WSW at 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges. Temperatures from lower 60s to the lower 70s.
Wednesday Afternoon
Mostly cloudy. Periods of showers & thunderstorms. Local downpours. Some storms could be strong to locally severe. Winds SW-WNW at 5-15 mph, with higher gusts. Temps in the 60s ( upper elevations ) to the low-middle 70s.
The Storm Prediction Center has issued a Marginal Risk for Severe Thunderstorm development during Tuesday Into Wednesday AM ( August 1 )
Storm Prediction Center Risk Regions
*Showers and downpours in thunderstorms will become likely into mid-late week. Heavy to locally excessive rainfall amounts will need to be closely monitored across the southern Appalachians.
Previous Headlines
*A drier and less humid air mass Saturday into early Sunday will give way to increasing moisture levels once again late Sunday into Monday ( July 30 ).
This will allow for cool nights, especially at upper elevations both Saturday and Sunday mornings, with a nice Saturday expected.
*Showers & downpours in thunderstorms will become likely next week with a locally heavy to excessive rain potential over the southern Appalachians and southeast USA.
Overnight Into Saturday Morning
Becoming clear. Cooler. Areas of dense fog, especially at middle to lower elevations. Winds NW-N 5-10 mph with higher gusts on mid-upper elevation mountain ridges into the overnight, then becoming light by morning. Temps from low-mid 50s at upper elevations to the upper 50s to around 60 degrees ( 40s possible in colder valleys at the upper elevations ).
Saturday Afternoon
Partly cloudy. Pleasant. Winds NW-NNE at generally less than 10 mph. Temperatures varying from 60s to lower 70s at upper elevations to 75-80 degrees.
Saturday Night Into Sunday Morning
Mostly clear ( some mid-high clouds ). Areas of dense fog in stream-river valleys ( especially at lower elevations ). Light easterly winds. Temperatures varying from 40s to low 50s in cooler valleys at upper elevations to the lower 60s.
Sunday Afternoon
Partly cloudy. Increasing haze and humidity with a chance of a hit or miss shower or thunderstorm. Light SE-S winds. Temperatures varying from low-middle 70s to the lower 80s ( coolest at upper elevations ).
Sunday Night Into Monday Morning
Becoming cloudy with a chance of showers & thunderstorms overnight into morning. Winds SE-S 5-10 mph, with higher gusts, on mountain ridges-exposed plateaus below 2700 ft. Winds S to SW 8-16 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures widespread in the 60s to around 70 degrees in warmer locations.
Monday Morning Through The Afternoon
Partly to mostly cloudy with a chance of showers and thunderstorms. Local downpours. Some storms could be strong to locally severe. Winds light SSE-SSW outside of thunderstorms. Temperatures varying from the lower 70s to the lower 80s.
Monday Night Into Tuesday Morning
A chance of showers & thunderstorms. Local downpours. Winds SSE-S at 5-15 mph on mountain ridges and plateaus below 2700 feet. Winds S-SW at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures widespread in the 60s. Areas of fog.
Tuesday Through Thursday
Periods of showers & thunderstorms. Locally heavy rain. Afternoon temperatures in the 60s to middle 70s will be common, especially in locations along and north of the High Knob Massif and Tennessee Valley Divide.
Weather Discussion ( Brief Break )
Early Monday ( July 30 ) Update
Increasing moisture levels will fuel intervals of showers and thunderstorms through the coming week. While some storms could become strong to locally severe, the greatest areal threat will be heavy to locally excessive rain amounts.
European Model 500 MB Height Anomalies: Days 1-5
A rather classic heavy rain setting for this time of year is being forecast by the European Model and its 51-Member Ensemble Mean, with general 1.50″ to 3.50″ basin average rainfall amounts during the work week ( implying much heavier local amounts will be possible ).
Previous Discussion
A brief break from the stormy, wet pattern for most of this weekend should be enjoyed before moisture increases again by the beginning of the work week.
High Knob Massif Webcam – University Of Virginia’s College At Wise
A wet Friday afternoon found 1.00″ to 2.00″ of rain falling in the Norton-Wise-Coeburn area, especially over the City of Norton into Coeburn and adjacent northern slopes of the High Knob Massif.
Little to no rain fell to the south at Big Cherry Dam where around 7.00″ of July rain have been measured, illustrating the local nature of heavy Friday afternoon downpours ( more than 4.00″ of rain fell at Big Cherry Dam in the past week to generate overflow ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 3-7
Another deepening upper air trough will set the stage for more heavy to locally excessive rainfall during the last days of July into early August.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
While details remain to be worked out, the European Model ensemble mean is forecasting heaviest rains to fall over the southern Appalachians and along the Coastal Plain as deep tropical flow develops around strengthening Bermuda High pressure in the western Atlantic Ocean.
