ALERT For Cold Night-time Conditions In Mountain Valleys, With Frost And Local Freezing Conditions By Sunday & Monday Mornings ( October 1-2 ).
While foggy river valleys and exposed mountain ridges-plateaus will remain well above freezing, a very dry air mass + clear skies sets the stage for a large vertical temperature difference to form during coming days. Coldest valleys in higher elevations may dip into the 30s by Friday and/or Saturday mornings, but the coldest and most widespread chill is expected Sunday & Monday mornings when 30s will become widespread in mountain valleys ( with 20s in coldest valleys of the High Knob Massif-Burkes Garden areas ).
Overnight Into Thursday Morning
Becoming partly to mostly cloudy by morning. Cloud bases dropping onto highest mountain ridges. NNW-NNE winds at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges. Areas of dense river valley fog. Temps varying from upper 40s to lower 50s in cooler mountain valleys to the low-mid 60s.
Thursday Morning Through The Afternoon
Mostly cloudy. Turning cooler. Small chance of showers or sprinkles. NNW to N winds 5 to 10 mph, with some higher gusts. Temps varying from lower 60s in upper elevations to the upper 60s to lower 70s, dropping by mid-late afternoon into the 50s at upper elevations and the lower-middle 60s at elevations of Norton-Wise.
Thursday Night Into Friday Morning
Becoming partly to mostly clear. N-NNE winds 5-10 mph, with some higher gusts, on mid-upper elevation mountain ridges. Chilly. Temperatures dropping into the lower 40s to lower 50s, except 30s in coldest mountain valleys ( above 2500-3000 feet ) in the Cumberland-Allegheny mountains.
Friday Afternoon
Partly to mostly sunny ( deep blue skies ). NNW-N winds at 5-10 mph, with some higher gusts. Temperatures varying from mid-upper 50s in upper elevations to the mid 60s to around 70 degrees ( warmer south into the Great Valley ).
Friday Night Into Saturday Morning
Partly cloudy. Chilly. NNW-NNE winds 5-10 mph, with higher gusts, on middle-upper elevation mountain ridges. Temperatures varying from 30s in colder mountain valleys to the lower 40s to around 50 degrees. Wind chills in the upper 30s to low 40s along high ridges.
Saturday Afternoon
Sunny. Deep blue skies. Cool. NNE-NE winds 5-10 mph, with some higher gusts. Temperatures varying from lower to middle 50s in upper elevations to the middle-upper 60s.
Saturday Night Into Sunday Morning
Clear. Cold. Winds becoming SE at 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temps varying from upper 20s to lower 30s in coldest mountain valleys to the mid-upper 40s on exposed ridges.
A frontal boundary will be crossing the mountains during Friday Night into Saturday Morning, with any initial clouds expected to give way to deep blue skies during Saturday.
High Knob Naturalist Rally Forecast – Updated Saturday – September 30
Partly cloudy to clear morning conditions are expected with NNE winds at 5-15 mph ( the higher wind speeds being at the High Knob Lookout ). Morning temperatures in the low-mid 40s will rise into the lower-middle 50s by afternoon.
9:00 AM at High Knob Lookout – Mostly Sunny. NNE to NE winds at 5-15 mph, with higher gusts. Temperatures in the middle 40s. Wind chills in the 30s to lower 40s.
3:00 PM at High Knob Lake – Sunny. Gorgeous blue skies. NNE winds 5-10 mph. Max temp 56-58 degrees at 2:30 to 3:00 PM, dropping quickly after 4:30 to 5:00 PM.
Weather Discussion ( Autumn Taste )
A true taste of autumn will be felt by Friday into Saturday, just in time for the 11th Annual High Knob Naturalist Rally.
Early Autumn at High Knob Lake Recreation Area – September 23, 2017
*As of September 29 autumn color was not as good as it was on September 23, with many early changing leaves having fallen. Chilly nights upcoming will have to stimulate a new wave of changes in an autumn that has been unusual with strong early color changes fading amid recent warm, dry days.
This photograph taken on September 16 illustrates the strong early color changes in the high country, looking across the lofty High Knob Lake Basin. Today ( September 29 ) nearly all the trees seen below with color are bare, with leaves having fallen.
Looking Across High Knob Lake Basin – September 16, 2017
Ten consecutive days, from September 19-28, featured MAX temperatures between 70 and 76 degrees at High Knob Lake. Nearly all the 3.50″ to 4.00″ of September rainfall fell during September 1-15 ( recent dryness also aiding the leaf drop ).
Afternoon maximum temperatures on September 29 felt like autumn, varying from around 60 degrees in cooler places of the High Knob Massif to 71 degrees in Clintwood.
An Alert For Frost And Freezing Temperatures Will Likely Be Needed For Parts Of The Mountain Area By This Weekend ( * ).
*River valleys and typically milder thermal belt ridges may be able to escape freezing temperatures, versus colder mountain valleys, but those with flowers and late season crops should stay tuned for later updates on this first major push of autumn air.
Meanwhile, Hurricane Marie will influence the mountain region with high clouds at times during the next few days. A general subsidence, or sinking air, regime will be a main influence that will continue to help support unseasonably warm conditions ( especially by day ). Air flow around her circulation field will also be a factor in wind directions.
Overnight Into Monday Morning
Partly cloudy ( high clouds streaming off Hurricane Marie ). Large vertical temperature spread between colder valleys and exposed mountain ridges-plateaus. SE winds 5-10 mph, with higher gusts, along mid-upper elevation ridges. Temps varying from 40s colder mountain valleys to low-mid 60s. Areas of dense river valley fog.
Monday Afternoon
Partly sunny ( high clouds may continue to stream off Marie into the region ). Unseasonably warm. Easterly winds less than 10 mph in most places. Temperatures varying from the lower 70s in upper elevations to the upper 70s to lower 80s ( warmer south into the Great Valley ).
Monday Night Into Tuesday Morning
Mostly clear. Light winds in valleys. Winds ESE-SSE at 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges. Large vertical temperature spread between colder valleys and milder ridges-plateaus. Temperatures varying from 40s to lower 50s in the colder valleys to the lower-middle 60s. Areas of dense fog within main river valleys and around larger lakes.
Tuesday Afternoon
Partly-mostly cloudy. Light northerly winds generally less than 10 mph. Temperatures varying from lower 70s in the upper elevations to the lower 80s ( warmer south into the Great Valley and within lower elevations of river basins ).
Tuesday Night Into Wednesday Morning
Partly-mostly cloudy. Light northerly winds, except breezy along highest mountain ridges. Milder with temperatures generally in the 50s ( valleys ) and 60s ( ridges ).
Preliminary Outlook – High Knob Naturalist Rally
My initial outlook is forecasting clear skies and chilly conditions with a classic, deep blue afternoon sky above High Knob Lake on September 30. A northerly air flow is expected, especially for those who visit High Knob Lookout where conditions will mainly feel like 40s during the day.
Morning temperatures in the 30s to lower 40s will only rise into the low-mid 50s by 2:00 to 3:00 PM at High Knob Lake, then drop back into the 40s and 30s on Saturday evening. Generally an ideal forecast for those seeking a taste of the high country in early autumn. Hope to see you there!
Following morning lows in the 40s and 50s in mountain valleys, with low-mid 60s on ridges, another unseasonably warm day was observed. Monday afternoon maximums reached low 70s on High Knob and low 80s in Clintwood, with my official NWS max being 81.1 degrees.
My update this afternoon includes the first preliminary forecast for the 11th Annual High Knob Naturalist Rally. This forecast will become more detailed later in the week.
Meanwhile, a nice little group of stationary lenticular mountain wave clouds are featured at sunset on Monday ( September 25 ) as viewed from the High Knob Massif Webcam located on top of the Computer Science-Mathematics Building on campus.
High Knob Massif Webcam – University Of Virginia’s College At Wise
These clouds are being generated by east-northeast air flow streaming across the massif from the broad circulation field associated with Hurricane Marie.
NAM 12 KM Model 10-Meter Wind Field At 2:00 PM on September 25, 2017
A general subsidence regime is ruling, but orographic lifting along the High Knob Massif is taking advantage of just enough moisture to develop this group of stationary lenticular wave clouds.
Like Monday morning, when low temperatures reached the mid-upper 40s in cooler valleys, this will support another chilly night in typically cooler valleys of mid-upper elevations as the dry air allows for a large diurnal temperature spread in valleys.
NAM 12 KM Model 850 MB Wind Field At 2:00 PM Monday – September 25, 2017
Previous Discussion
Early Autumn at High Knob Lake Recreation Area – September 23, 2017
Although conditions vary significantly across the area, color continues to develop across the high country and is currently varying from green trees to bare trees!
Approaching Sunset At Upper Norton Reservoir – September 23, 2017
Big weather changes continue to look likely just in time for the 11th Annual High Knob Naturalist Rally, with 40s to mid 50s day-time temperatures ( at max heating ) currently in my forecast. A detailed forecast will be issued later.
Hurricane Marie – Overnight Of Monday – September 25, 2017
High clouds from Hurricane Marie are moving overhead tonight as she spins closer to the eastern coastline of the USA. Although chances for rainfall are looking to increase into the first week of October, the nearby presence of Marie will in part hinder precipitation development along and in advance of the first strong autumn cold front that sweeps into the region later this week ( pushing Marie away ).
National Hurricane Center Forecast Track
Tropical Storm Watches are in effect for eastern North Carolina.
Marie will impact our weather in a number of different ways, as already highlighted above, with winds along highest mountain crestlines being a little gustier even tonight due to a SE flow forced by the large wind field circulating around Marie. Winds will shift in direction through coming days as Marie changes her position.
Partly to mostly clear. Areas of dense valley fog. Light winds. Large vertical temperature spread developing between cooler valleys and milder ridges & plateaus. Temperatures varying from upper 40s to lower 50s in cooler mountain valleys to the lower-middle 60s.
Friday Afternoon
Partly to mostly sunny. Warm. Light NE-ENE winds. Small chance of an isolated shower or sprinkle. Temps varying from upper 60s to lower 70s in the upper elevations to upper 70s to lower 80s ( warmer into the Great Valley ).
Friday Night Into Saturday Morning
Partly-mostly clear ( some high clouds possible ). Areas of dense valley fog. Light winds. Large vertical temperature spread developing between cooler mountain valleys and milder ridges & plateaus. Temperatures varying from the 40s in colder mountain valleys to the lower-middle 60s.
Saturday Afternoon
Mostly sunny. Unseasonably warm. Light NNE-NE winds. Temperatures varying from lower to middle 70s in upper elevations to the low-mid 80s.
Saturday Night Into Sunday Morning
Clear. Areas of dense valley fog. Large vertical temp spread developing between colder valleys & milder ridges-plateaus. Temperatures varying from low-mid 40s in colder valleys to the middle 50s to around 60 degrees. Light SE-SSE winds generally less than 10 mph on mid-upper elevation ridges.
Sunday Afternoon
Mostly sunny ( some high clouds possible ). Unseasonably warm. Light easterly winds. Temperatures varying from low-mid 70s in upper elevations to upper 70s to lower 80s. Around 70 degrees at highest elevations.
Sunday Night Into Monday Morning
Mostly clear. Areas of dense valley fog. Large vertical temp spread developing between colder valleys and milder ridges and plateaus. Temperatures varying from 40s in the colder valleys to the mid 50s to around 60 degrees.
A major weather pattern change featuring a shift to below average temperatures is being monitored for the last days of September into early October. Chilly conditions are currently expected for the High Knob Naturalist Rally on September 30.
High Knob Naturalist Rally – September 30 at High Knob Lake Recreation Area
Weather Discussion ( Change In Sight )
Reference My Updated Weather Trend for the upcoming High Knob Naturalist Rally, and the Hellbender-Cloudsplitter races, to look at a major pattern change across North America.
Saturday Morning Update
NASA Visible Image At 8:30 AM – September 23, 2017
The view this Saturday morning features a rather typical scene with an array of dense valley fog marking the Clinch, Cumberland, New, Russell Fork-Levisa Fork-Tug Fork of the Big Sandy and many more streams beneath an array of scattered high altitude clouds.
A large sunrise temperature spread from upper 40s to lower 50s in cooler mountain valleys to the lower-middle 60s on exposed ridges and plateaus will kick start an unseasonably warm Saturday for the first full day of astronomical autumn.
Have a great day.
Previous Discussion
High Knob Massif Webcam – University Of Virginia’s College At Wise
The current weather pattern is the epitome of persistence, with mostly clear skies by night that feature large vertical temperature spreads between colder mountain valleys and milder ridges-plateaus, along with an array of dense valley fog, followed by building day-time clouds and localized to very widely scattered showers and sprinkles.
High Knob Massif Webcam – University Of Virginia’s College At Wise
The only real changes through this weekend into early next week will be for some drying of the vertical column to help enhance diurnal temperature spreads. That translates into a continuation of unseasonably warm conditions by day and cool temperatures by night ( especially amid middle-upper elevation mountain valleys where down right chilly temps will continue to be felt ).
European Model 500 MB Height Anomalies Forecast – 8 AM Saturday ( Sept 30 )
The European Model, and its ensembles, remain very steady in forecasting a significant ( major versus this current air mass ) cooling trend across much of eastern North America by later next week into next weekend. Just in time for the 11th Annual High Knob Naturalist Rally.
If the axis of the 500 MB trough is actually still back west of the mountains, as forecast above, this could also mean unsettled or wet conditions; however, it is too soon yet to know.
European Model 850 MB Temp Anomalies Forecast – 8 AM Saturday ( Sept 30 )
Due to changes ongoing at high latitudes a forecast cooling seems increasingly likely, with the 0 degree Celsius line at 850 MB dropping down across New England and much of the Great Lakes by next weekend. Changes, of course, will occur in these details, but the trend is looking strong for a major flip in the pattern across eastern North America.
While a significant pattern change into chilly conditions will occur by the end of September and beginning of the new month of October, the most recent trend now finds a majority of the European Ensemble members warming temperatures back to above average by race weekend.
European Model 850 MB Temp-Streamline Forecast at 8 AM Saturday ( Sept 30 )
Although I highlight the operational European Model, the mean of the 51-Member Ensemble Group continues to show a shift to unseasonably cool conditions that will impact the 11th Annual High Knob Naturalist Rally.
High Knob Naturalist Rally – September 30, 2017
This will create chilly conditions for the rally, as well as for any racers who may be in the region to practice.
Early Autumn at High Knob Lake Recreation Area – September 23, 2017
Eagle Knob of High Knob Massif Elevation 4188 feet
Average Daily MAX: 62.1 degrees Average Daily MIN: 51.4 degrees September 1-23 MEAN: 56.8 degrees Highest Temperature: 73 degrees Lowest Temperature: 41 degrees Total Precipitation: 3.50″ to 4.00″
Conditions observed during September 1-23
High Knob Lake Elevation 3527 feet
Average Daily MAX: 64.8 degrees Average Daily MIN: 50.4 degrees September 1-23 MEAN: 57.6 degrees Highest Temperature: 76 degrees *Lowest Temperature: 41 degrees
*Middle 30s occurred in the colder valleys, with average nightly lows for the September 1-23 period being in middle-upper 40s.
The new development is beyond this time, with a shift back toward eastern-central USA ridging and troughing over the Pacific Northwest leading up to the weekend of the races.
European Model 500 MB Height Anomalies – Valid At 8 AM October 5, 2017
The operational European Model ( above ) has support of all but approximately 14 members of the 51-member ensemble group ( mean of the group below ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
If this new trend is accurate, it would lead to above average temperatures returning in time for race weekend ( Oct 7-8 ). Positioning of height centers, above, would also suggest a continuation of mainly dry conditions.
Stay tuned for updates as race weekend gets closer in time and details become more clear. The first detailed forecast for these races will be made by the middle of next week.
Mostly clear. Large vertical temperature spread between colder valleys and milder ridges & exposed plateaus. Areas of dense valley fog. Light winds. Temperatures varying from lower-middle 40s in colder mountain valleys to the upper 50s to around 60 degrees exposed ridges-plateaus.
Monday Afternoon
Partly to mostly cloudy at times. Small chance of sprinkles. Light northerly winds. Temps varying from mid-upper 60s in upper elevations to the middle 70s to around 80 degrees.
Monday Night Into Tuesday Morning
Mostly clear. Areas of dense valley fog. Light northerly winds below 2700 feet. SE winds 5 to 10 mph, with some higher gusts, along mid-upper elevation mountain ridges. Large vertical temperature difference developing between colder mountain valleys & milder ridges-exposed plateaus. Temperatures varying from 40s in colder valleys at upper elevations to the upper 50s to lower-mid 60s.
Tuesday Afternoon
Partly to mostly cloudy. Chance of rain showers. Thunder possible. Winds becoming NW-NE generally less than 10 mph. Temps varying from 60s in upper elevations to the middle 70s to around 80 degrees.
Tuesday Night Into Wednesday Morning
Partly-mostly cloudy. Chance of showers-thunderstorms. WNW to NW winds 5-10 mph, with some higher gusts, on middle-upper elevation mountain ridges. Areas of locally dense fog. Temps varying from 50s to lower-middle 60s.
Wednesday Afternoon
Partly to mostly cloudy. Chance of showers-thunderstorms. WNW-NW winds generally less than 10 mph. Temperatures varying from 60s in upper elevations to the mid-upper 70s.
High Knob Massif Webcam – University Of Virginia’s College At Wise
A beautiful sunset to mark the close of the first work day of these final days of astronomical summer. Afternoon maxs varied from 60s in upper elevations of the High Knob Massif to the 70s across low-middle elevations in Norton-Wise and the Clintwood area ( around 80 degrees in Haysi-Grundy ).
Clintwood 1 W National Weather Service Station
Monday began with a large vertical temperature spread that is typical of the mountains. Readings at sunrise varied from 40s in colder valleys of the High Knob Massif to upper 50s to lower 60s on exposed mid-elevation mountain ridges.
*The AM MIN actually only fell to 63.9 degrees at the Flatwoods Mountain Mesonet adjacent to Pine Mountain along the Kentucky side of the stateline ( generating a nearly 20 degree difference between coldest valleys and mildest ridges ).
Nora 4 SSE National Weather Service Station
This temperature data is, of course, from highly accurate and well shielded instruments and not roof-top sensors or other small solar radiation equipped stations.
*My study on solar radiation shields indicates that day-time temperatures tend to run 1 to 3 degrees, occasionally more, above what official National Weather Service sensors with larger shields record. It is very important to realize that the design and size of the solar radiation shield used is vital to accurate data collection.
*I should have noted that the above study was over a natural surface of grass. If sensors are not over a natural surface, or located near roof-tops or parking lots, then the skew ( error ) will be much greater by day due to heat liberation and advection from anthropogenic surfaces. So placement and instrumentation are critical to accurate temperature recording of the true air temperature for long-term climate documentation and analysis.
Clintwood 1 W National Weather Service Station – September 1-18, 2017
The only changes to my update is to increase the chances for showers, with thunder possible, from late Tuesday into Wednesday, with the European Model continuing to show best chances being during Wednesday ( the NAM Model begins best chances Tuesday evening into Wednesday ).
Category 5 – Hurricane Marie
Meanwhile, Hurricane Marie has just been upgraded to a CAT 5. Although truly a majestic storm from new GOES-16 visible imagery ( below ), this is yet another tragedy for places to be impacted in coming hours.
Hurricanes Marie and Jose – Beginning Of A Fujiwhara
Monday afternoon offered the first GOES-16 visible images that show the developing connection between Marie ( lower right ) and Jose ( off the Virginia coast ), with upper-level outflow from Jose reaching down to the anticyclonic spin of intensifying Hurricane Marie.
Previous Discussion
Early Autumn In Big Cherry Lake Wetland Valley – September 16, 2017
Seasonally cool nights in mountains valleys, and mild to warm days, will be featured this week along with cloud development by day. Only a small chance of sprinkles or rain showers is currently in my forecast, with Wednesday afternoon looking to have the best chances. A typical array of dense valley fog formation is expected by night.
Early Autumn At High Knob Lake – September 16, 2017
An array of early color changes are on display across the high country of the High Knob Massif. Most places have some early color changes, to a more limited extent, following a rather cool first half of September.
Early Autumn At Upper Norton Reservoir – September 16, 2017
The tropics will again be the main focus this week, with the European Model group suggesting that Jose and Marie may do a Fujiwhara Dance with each other; although, details of this dance routine are still being choreographed!
The Fujiwhare effect in meteorology is named for Japanese meteorologist Sakuhei Fujiwhara who first described the interaction of two vortex centers about each other. A connection between their circulations becomes increasingly evident over time as the effect develops ( initially they are far removed with no clear interactions between each other, as seen early on September 18 ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
Upper-level ridging over eastern North America into the western Atlantic is the main factor expected to play into this dance, with no clear steering flow yet seen to carry these hurricanes out to sea. This is the same system that will limit rain amounts this week and contribute to a mild to warm pattern ( with mountain valley coolness being a terrain driven feature more than a synoptic-scale one ).
There are increasing signs of a significant upper-level shift back to unseasonably cool conditions by the final days of September into the beginning of October.
Low clouds & widespread dense fog will dominate upper elevations of the High Knob Massif-Black Mountain area into Thursday. Areas of dense fog will also be possible in middle elevation gaps, such as Little Stone Mountain Gap along U.S. 23 between the City of Norton & Big Stone Gap.
Overnight Into Thursday Morning
Low clouds with occasional showers. Dense fog widespread at upper elevations and locally in middle elevations along and southwest of the High Knob Massif-Tennessee Valley Divide ( e.g., near Powell Valley Overlook ). SW winds 6-18 mph, with gusts 20 to 30 mph, along mid-upper elevation mountain ridges & plateaus. Temperatures varying from upper 40s to the upper 50s ( coolest at highest elevations where wind chills will be 40-45 degrees in gusts ).
Thursday Afternoon
Cloudy. A chance of showers. Dense fog ( low clouds ) at upper elevations. SSW-WSW winds 5-15 mph, with some higher gusts on mountain ridges. Temperatures varying from mid-upper 50s to mid-upper 60s ( coolest within the highest elevations ).
Thursday Night Into Friday Morning
Mostly cloudy. A chance of showers. Low clouds continuing at high elevations. Winds becoming light & variable. Temps varying from upper 40s to lower 50s in upper elevations to the mid 50s to around 60 degrees. Areas of dense fog.
Friday Afternoon
Becoming partly sunny. Pleasant. Light winds. Temps varying from low-mid 60s in upper elevations to the lower to middle 70s.
Friday Night Into Saturday Morning
Mostly clear. Light winds. Large vertical temp spread developing between mountain ridges & valleys. Temps varying from low-mid 40s in colder mountain valleys to upper 50s to lower 60s on exposed ridges. Areas of dense valley fog ( especially in lower elevations ).
Weather Discussion ( Gloomy )
Another day of gloomy, damp conditions with a chance of showers is featured before a much improved TGIF arrives.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Conditions deteriorated late Wednesday as low clouds and rain showers returned with the decaying remnants of Irma.
Lonesome Pine Airport In WiseHigh Knob Massif Webcam – University Of Virginia’s College At Wise
Conditions continue to be chilly, especially in the high country where afternoon temperatures struggled to break 60 degrees at the summit level of the High Knob Massif prior to falling to around 50 degrees with rain showers.
*Strong SW winds gusting over 30 mph at times made it feel even cooler. This was in contrast to afternoon temps that reached into the lower 70s in Clintwood on a downsloping SW flow.
Black Mountain Mesonet
A notable improvement in conditions will be enjoyed Friday into this weekend. This marks a shift in the pattern toward above average temperatures, especially by day, which looks to dominate next week.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
A flip in the upper air pattern across North America, with eastern USA troughing being replacing by ridging as a deep trough digs into the western USA ( above ) will be associated with a shift toward above average temperatures ( below ).
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: Days 6-10
A bad aspect of such a pattern will be the potential for more tropical threats to the USA during the next week to 10 days.
An Alert For Strong & Gusty Winds For Monday Into Tuesday As The Pressure Gradient Tightens With The Inland Movement And Weakening Of Hurricane Irma
Strong and gusty winds are expected to develop at high elevations by the overnight-morning hours of Monday, then increase across middle-lower elevations by later Monday into Tuesday morning.
Wind speeds of 20 to 40 mph are expected at elevations below 2700 feet, with 40 to 60 mph, or locally higher in gusts ( along mountain ridges and in high gaps ), at elevations above 2700 to 3000 feet.
Overnight Into Sunday Morning
Clear. Chilly. Large vertical temperature difference between colder mountain valleys and milder ridges. Winds E-SE at 5-15 mph, with some higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from 30s within colder mountain valleys to the upper 40s to low 50s on exposed ridges. Areas of dense river valley-lake fog.
Sunday Afternoon
Mostly sunny. Pleasant. Winds ENE-E at 5-10 mph, with some higher gusts along mountain ridges. Temperatures varying from the low-mid 60s at upper elevations to the lower-middle 70s.
Sunday Night Into Monday Morning
Increasing high clouds overnight into morning. Increasing winds at high elevations. Winds E-ESE at 10-20 mph, with higher gusts, along mid-upper elevation mountain ridges. Wind gusts near 40 mph at highest elevations by sunrise. Temperatures varying from the 40s to low-mid 50s.
Monday Afternoon
Mostly cloudy. Showers developing. Winds ENE-ESE at 10-20 mph, with higher gusts, at elevations below 2700 feet. Winds ENE-ESE at 20-30 mph, with gusts over 40 mph, on mid-upper elevation mountain ridges. Cool with temps mainly in the 50s to lower 60s ( coolest upper elevations where cloud bases will lower ).
Monday Night Into Tuesday Morning
Rain showers. Downpours possible, especially along the windward slopes-crestlines of the High Knob Massif and Tennessee Valley Divide. Windy. Winds ENE to E at 15-25 mph, with higher gusts on mountain ridges-plateaus, below 2700 feet. Winds ENE-ESE at 25-35 mph, with gusts of 40-60 mph, at elevations above 2700-3000 feet. Low clouds with widespread dense fog at upper elevations. Temps varying from around 50 degrees at high elevations to the mid 50s to lower 60s.
An initial surge of rain from the remnants of Irma will impact the mountain region late Monday into Tuesday, then a possible break for a prolonged period may occur until rain chances increase again during mid-late next week for locations west and northwest of the Blue Ridge province.
Rainfall amounts are expected to vary widely across the southern Appalachian region. Heaviest totals are expected to fall along the Blue Ridge, from the Meadows of Dan southwest through western North Carolina. Least amounts are expected near and northwest of the Virginia-Kentucky state line, and within portions of the Great Valley of eastern Tennessee, where totals of 0.50-1.00″ or locally less are most likely on downsloping winds.
Rainfall totals of up to 3.00″ to 6.00″+ are expected along the Blue Ridge in southwestern-western North Carolina. Max rain amounts are likely near Lake Toxaway, Nc., with other enhanced totals in the Mount Mitchell ( Black Mountains ) and Grandfather Mountain areas. Secondary maximums of up to 1.50-2.50″+ will be possible in the High Knob Massif-Black Mountain corridor of southwestern Virginia on upsloping low-level air flow.
Weather Discussion ( All About Irma )
For the fourth consecutive night temperatures are in the 30s amid colder mountain valleys of the High Knob Massif, with low 40s here in Clintwood ( 42.8 degrees at 4:00 AM ).
This weather period will be all about the approach and inland movement of destructive and powerful Hurricane Irma. Although passing far southwest of the Mountain Empire, the pressure gradient will initially become so strong that impacts can not be escaped.
Infrared Image Of Hurricane Irma At 3:47 AM on September 10, 2017
Irma has regained CAT 4 status after weakening along the coast of Cuba following interaction of its circulation with hilly to mountainous terrain. Pressure has dropped back down to 928 mb as of 4:00 AM Sunday. An additional gain in strength will be possible over very warm water today.
National Hurricane Center Official Track At 2:00 AM Sunday
The track forecast has continued to ease west to place the entire Gulf Coast of Florida in a grave position through coming hours of Sunday into early Monday.
Spaghetti Model Cluster As of 2:00 AM Sunday on September 10, 2017
Most models are now taking the remnant low into western portions of Kentucky and Tennessee as it becomes extra-tropical, with possible subsequent movement back to the east-northeast during mid-late this week.
NAM 12 KM Model Total Rainfall Forecast Next 84-Hours
Any flooding rains are most likely along the Blue Ridge where strong orographic lift will enhance amounts late Monday into Tuesday ( I will not be surprised to see up to 10.00″+ in the Lake Toxaway and Highlands area of south-western North Carolina where tropical moisture will be initially lifted upward into the higher elevations on very strong upslope flow ).
Although no flooding is expected, local rain amounts could vary significantly from a max over the high country of the High Knob Massif to low amounts along the Kentucky side of the border on strong downsloping E-SE air flow. Some places along the Virginia-Kentucky border may pick up the most rain later this week when air flow shifts southwest and whatever is left of Irma’s extratropical low moves eastward toward the lower Ohio Valley.
Meanwhile, strong & gusty winds will develop Monday and Tuesday ( first at high elevations before mixing downward into middle-lower elevations ). Local power outages can not be ruled out until the remnant low fills and the very strong pressure gradient weakens into mid-week.
A strong cold front will transport a cool, early autumn air mass into the mountains by Wednesday. Unseasonably cool temps are expected through the upcoming weekend, with widespread night-time temperatures dropping into the 40s. Colder mountain valleys will fall into the 30s on coldest nights, with near freezing to even below freezing conditions not impossible amid coldest valleys at upper elevations in the High Knob Massif-Burkes Garden corridor ( with the full cooling potential dictated by sky cover and wind ).
Overnight Into Tuesday Morning
Mostly clear to partly cloudy. Breezy to gusty winds over mountain ridges. SSW-SW winds 5 to 15 mph, with higher gusts on mountain ridges-plateaus below 2700 feet. Winds SW-WSW 10-20 mph, with higher gusts, along mountain ridges above 2700 feet. Temperatures varying from 50s in sheltered valleys to the 60s on exposed ridges-plateaus. Areas of dense river valley-lake fog at low elevations.
Tuesday Afternoon
Showers & thunderstorms becoming likely. Downpours possible. SSW-WSW winds 10-20 mph, with higher gusts, along middle-upper elevation mountain ridges-plateaus. Temperatures varying from the low 60s to the lower 70s, coolest in upper elevations. Low clouds-fog forming in areas of showers-storms.
Tuesday Night Into Wednesday Morning
Showers & thunderstorms tapering to showers & drizzle. Winds shifting to NNW-NNE at 5-15 mph, with higher gusts on mid-upper elevation mountain ridges. Temperatures dropping into the 50s ( mid-upper 40s highest elevations ). Low clouds and locally dense fog becoming widespread at mid-upper elevations along and north to northwest of the High Knob Massif-Tennessee Valley Divide.
Wednesday Afternoon
Partly-mostly cloudy. Much cooler. A chance of instability showers beneath increasing cold air aloft. Light NNW-NNE winds generally less than 10 mph. Temps varying from the low-mid 50s in upper elevations to the low-mid 60s.
Wednesday Night Into Thursday Morning
Partly cloudy. Chilly. Winds NW-N at 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures dropping into the 40s, with 30s in colder mountain valleys. Areas of dense river valley fog.
Thursday Afternoon
Partly to mostly sunny. Cool and crisp. Winds WNW-NW at 5-10 mph, with higher gusts along mountain ridges. Temps varying from low-mid 50s to the low-mid 60s.
Thursday Night Into Friday Morning
Mostly clear to partly cloudy. Chilly. Light winds on mountain ridges ( calm wind in valleys ). Temperatures widespread in the 40s, with 30s within colder mountain valleys ( 30 to 35 degrees in the coldest valleys at upper elevations ). Areas of dense river valley and lake fog at lower elevations.
Friday Afternoon
Mostly sunny. Blue skies. Light northerly winds generally less than 10 mph. Temperatures varying from upper 50s to lower 60s in upper elevations to the upper 60s to low 70s.
Friday Night Into Saturday Morning
Mostly clear. Chilly. Large vertical temperature spread developing between colder valleys & milder ridges. Winds NNE-NE at 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from the 30s in colder mountain valleys to low-mid 50s on exposed mountain ridges-plateaus. Locally dense river valley fog.
The approach of Major Hurricane Irma toward the southeastern USA will be the big weather story heading into this weekend, with potential impacts to the southern-central Appalachians being monitored for next week. Stay tuned for later updates.
Weather Discussion ( Autumn Chill )
Thursday Evening Update
You know the night ahead will be cold when temps in the high valleys drop into the 40s before 8:00 PM, under mainly clear skies and developing drainage flows.
AM Low Temperatures September 7, 2017
Jefferson 2 E, NC 37 degrees
Transou, NC 37 degrees
Frost, WV 39 degrees
Tazewell, VA 39 degrees
Burkes Garden, VA 41 degrees
Shady Valley, TN 41 degrees
Canaan Valley 2, WV 43 degrees
It is not just the ice box of the Big Cherry Lake basin that is getting cold, as noted by low temperatures reported across the mountain region early on September 7 ( I suspect that the Big Cherry was coldest, as later data will determine ).
Low temperatures into the morning hours of September 8 will be even colder, especially within the most favored cold places of Canaan Valley, Burkes Garden, and the Big Cherry.
National Hurricane Center Irma Track Forecast – 8 PM September 7, 2017
Meanwhile, the forecast for CAT 5 Irma continues to look ominous and extremely severe for Florida.
European 51-Member Ensemble Cluster Forecast Track At 8 AM Sept 7
Significant impacts are likely into the southern Appalachians. Stay tuned for later updates.
Tuesday Evening Irma Notes
Pressure was used to rank hurricanes from 1850 into the 1990’s before a shift to only using wind speed.
List of Strongest Atlantic Basin Hurricanes By Pressure
+Indicates strength was not continuous ( these systems fell below CAT 5 then regained that status at least once during their lives ).
Atlantic Basin Hurricane Ranks Using Wind Speed
Irma is in second place, tied with the 1935 Labor Day beast, Gilbert, and Wilma, if using wind speed alone.
Lower pressure generally = stronger winds, but not always, and total destruction and energy released is certainly often caused by more than just winds ( as Harvey exemplifies ).
It can be argued that there are many ways to rank such monsters, including death toll and total destruction. It is even more difficult to place a rank on pure misery and suffering by humans and all species of life impacted.
Previous Discussion
A mass of true autumn air will push into the mountains by Wednesday into Thursday behind the passage of a strong cold front, featuring showers & possible thunderstorms during Tuesday into early Wednesday.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Following a chilly beginning to Labor Day ( Monday ), with lower 40s to lower 50s widespread in mountain valleys, an increase in low-level haze was notable into the afternoon as temperatures peaked in the middle-upper 70s from Norton-Wise to Clintwood and mid-upper 60s at high elevations in the High Knob Massif.
NAM 12 KM Model Total Rainfall Forecast
The focus now shifts to a developing eastern USA trough and strong cold front, with a true push of early autumn air into the central-southern Appalachians in coming days.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5
For a week, or more now, this anomalous push of chilly air has been well defined and forecast by the ensemble mean of the European Model group. Only details of how cold it gets in any given place are yet to be determined, largely based upon if skies can remain clear and boundary layer winds decouple from the large-scale flow field on any night during the September 6-10 period.
It is a no brainer that colder mountain valleys will drop into the 30s at some point, the only question is if any of the infamous frost pockets can actually reach freezing or a little below ( such as those highlighted in my Summer 2017 Data section ) in days ahead.
Freezing conditions have at some point in time occurred during every month of the year within these most favored places, so it is certainly not unprecedented by any stretch to have such occur during early September ( the start of Meteorological Autumn ).
National Hurricane Center Track Forecast At 11 PM Monday – September 4, 2017
The big story in the weather world, of course, will be major hurricane Irma as it approaches the Islands and the USA.
Hurricane Irma Spaghetti Model Track Guidance
The main model cluster, as well as ensemble groups of both the GFS & European, show that there remains uncertainty with respect to track during the next week ( of course ). A major USA doomsday hit is not set in stone; although, it is also not in any way being ruled out. The main aspect at this point in time is prepare for the worst and hope for the best outcome. That includes the southern-central Appalachians.
GFS Model Mean Sea Level Forecast At 8:00 AM Sunday – September 10, 2017
The exact position varies from run to run on the models, but there is some considerable agreement, when putting all the ensembles from the European & GFS together, on a north-ward turn by this weekend. Exactly when and where that happens will then help better determine the implications.
GFS Model Mean Sea Level Forecast At 2:00 AM Tuesday – September 12, 2017
Certainly a much better handle on this setting will be had by later this week ( this is only Monday ), as part of the final outcome is going to depend upon how Irma tracks through the island chains and if she has any significant interaction with them and their mountains. Stay tuned for updates.
Northern Hardwood Forest In Upper Elevations of High Knob Massif
The Meteorological Summer period of 2017 consists of the months of June-July-August. The following data is courtesy of the High Knob Massif mesonet, part of the undergraduate research program of the University Of Virginia’s College At Wise ( UVA-Wise ).
Eagle Knob is part of three peaks ( locally called knobs ) that rise above 4,000 feet in the High Knob Massif, and a cluster of 15 peaks rising to 3,600 feet or higher in elevation within the 182 square mile ( nearly 120,000 acre ) massif area.
High Knob Lake of High Knob Massif – Peak of Rhododendron Bloom
High Knob Lake lies near the head of the 41.9 square mile watershed of Big Stony Creek of the Clinch River of the great Upper Tennessee River Basin.
Big Cherry Wetland Valley sites are situated in forest, forest edge, and open habitats to capture the range of conditions present along this important watershed area.
Big Cherry Wetland Valley is one of two upper elevation valleys forming the Big Cherry Lake basin and headwaters of the South Fork of Powell River ( a 40 square mile watershed of the Powell River of the Upper Tennessee River Basin ).
Mean summer temperatures in both the High Knob Lake and Big Cherry Lake basins have run cooler than both notorious frost pockets of Canaan Valley ( in the eastern highlands of northern West Virginia ) and Burkes Garden ( in southwest Virginia ), with the nocturnal low temperatures of the open valley expanse in Big Cherry Lake basin running 1.4 degrees cooler than in Canaan Valley ( 53.3 degree average low ) and 1.1 degrees lower than Burkes Garden ( 53.0 degree average nightly temperature during summer ).
Although I knew this was possible from decades of past research, the development and collection of high resolution and very high quality temperature data is now documenting this striking trend with average low temperatures since January 1 in Big Cherry Lake basin averaging 1.5 degrees cooler than Burkes Garden and just 0.1 degree lower than the higher latitude Canaan Valley 2 station.
Any good student of Appalachian climatology understands that any place which can even hang close to Canaan Valley and Burkes Garden in mean valley temperature, and especially with nocturnal mean temperature, has to be considered climatically unique.
Cove of Big Cherry Lake in High Knob Massif
Mean temperatures during Summer 2017 have run 10.0 to 12.0 degrees cooler, on average, than in the Tri-Cities of the Great Valley whose statistics are shown for comparison:
Tri-Cities NWS Station ( TRI ) Elevation 1519 feet
The average daily high temperature on Eagle Knob of the High Knob Massif was 17.1 degrees lower than observed at TRI ( 68.1 degrees versus 85.2 degrees ). The highest temp recorded on Eagle Knob was 8 degrees lower than the mean daily high experienced in the Tri-Cities.
This striking difference was also exemplified by low temps, with the lowest summer reading of 49 degrees at TRI being above the average nightly low of 47.6 degrees recorded at the Big Cherry Wetland Valley 4 site during June.
Lower-Middle Elevations of Dickenson County, Virginia
Some other data for comparison from the lower-middle elevations in the surrounding region:
Temperatures on the Wise Plateau, along the Tennessee Valley Divide, are similar to Nora 4 SSE ( also located near the Tennessee Valley Divide ) by day but tend to run cooler by night ( especially in places near drainages where cool air settles / the UVA-Wise recording site is along a S slope ).
With the above official data noted, I ask all forecasters WHY would they ever predict the same ( or even cooler ) temps by day in Grundy versus the Norton-Wise and Nora 4 SSE sites outside of an highly anomalous weather situation?
Grundy NWS Elevation 1170 feet
Average Daily MAX: 82.4 degrees Average Daily MIN: 60.1 degrees Summer MEAN: 71.2 degrees Highest Temperature: 94 degrees Lowest Temperature: 46 degrees ( 9 days at or above 90 degrees )
No days officially reached 90 degrees at UVA-Wise or at Nora 4 SSE during Summer 2017, while 9 days reached 90 degrees or higher in Grundy. Any one living or working within this area already knows the above, and also knows any forecast showing the same or cooler daytime MAXS in Grundy versus Norton-Wise is wrong nearly all the time. This also includes the Town of Clintwood, since days also tend to be cooler than in the lower elevation Levisa Fork Valley of the Town of Grundy.
Summer 2017 Rainfall Totals
Rainfall totals during summer were near average to below average, with a trend of below average June-July rainfall and above average August rain amounts.
Whitewater Gushes In South Fork Gorge of High Knob Massif
Whitesburg 2 NW Mesonet: 10.69″ UVA-Wise NWS: 12.77″ Grundy NWS: 12.98″ Clintwood 1 W NWS: 13.71″ Nora 4 SSE NWS: 16.29″ City of Norton Water Plant: 16.39″ Big Cherry Lake Dam: 16.87″ Flatwoods Mountain Mesonet: 16.98″ Coeburn Water Treatment Plant: 17.56″ *Eagle Knob of High Knob Massif: 18.40″ Black Mountain Mesonet: 19.77″
*Approximate total. Wetter places within the High Knob Massif-Black Mountain corridor had 18.00″ to 20.00″ of summer rainfall. Rain at Big Cherry Lake Dam was around 2.00″ below the average of the previous 9 summer seasons.
Actual totals varied across the area, as typical during the often chaotic convective season, with large differences over even short distances in many cases.
Nice Light Upon Whitewater Along The South Fork – High Knob Massif
Lake levels on all the water supply lakes from the Upper Norton Reservoirs to Appalachia Lake and Big Cherry Lake had dropped well below spillway marks by the beginning of August before a shift into a very wet pattern boosted most to overflow. The summer trend is shown graphically by the stream gauge on Big Stony Creek of the High Knob Massif.
Outside of local downpours, stream levels had been in general decline during June-July before widespread wetness cranked up the whitewater to ROARING levels in August.
Big Stony Creek of High Knob Massif
August rainfall totals of 7.74″ at the City of Norton Water Plant, on the northern base of the High Knob Massif, and as much as 8.00″ to 9.00″+ in the high country, saved Summer 2017 from being much below average in terms of rainfall.
The High Knob Hellbender 10K and Cloudsplitter 100 races remain more than a month away at the time of this initial outlook. So this certainly must be considered preliminary.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 5-9
Forecast’s such as this current 5 to 9 day outlook from the 51-Member European Ensembles are extended outward through time to generate the European Weeklies.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 5-9
I am not allowed to actually show the graphics of the weeklies, but they are currently forecasting a cooler than average temperature trend through September into early October, with near to above average precipitation.
Climate Prediction Center Outlooks
The Climate Prediction Center outlooks for September and Autumn 2017 are similar, predicting a cooler than average September followed by warming to above average to push mean fall temperatures above average.
Many changes begin occurring in the atmosphere during autumn, as the seasonal transition from summer toward winter begins in the Northern Hemisphere, making any given forecast uncertain for extended periods of time. Check back for later updates.
As race time gets closer a forecast designed specifically for the three-dimensional nature of the race courses, which are run across 2000-3000 vertical feet of elevation change, will be produced that accounts for the complex terrain and microclimatology of the High Knob Massif.
