Mountain Area Forecast ( Dec 31-Jan 2 )

ALERT For Strong SSW-SW Winds For New Year Eve’s Day ( Saturday ) Is Now In Effect.  ROARING SW Winds Will Develop At Upper Elevations First And Mix Down Into Middle & Lower Elevations Of The Cumberland Mountains During The Day Saturday.

*Following a decrease in winds Friday evening, the gradient tightens again by Saturday morning with another period of ROARING winds ( SW in direction this time ) throughout the daylight hours of New Year Eve’s Day.

A developing temperature inversion late Saturday into Sunday morning, with evaporative cooling, will then restrict strongest winds to highest elevations along top of the planetary boundary layer ( i.e., evaporative cooling will force decoupling as lower levels in the atmosphere cool relative to milder air aloft ).

*The Potential For Snow Or Frozen Precipitation Forms Needs To Be Monitored For New Year Eve’s Afternoon & Evening – Especially In The Southwest Upslope Flow Zone Of Wise, Scott, Lee Counties Along And SW Of The High Knob Massif – Tennessee Valley Divide.

Overnight Into Saturday Morning

Mostly clear.  Cold.  Winds becoming SSW-SW at 10-25 mph, with higher gusts, along middle-upper elevation mountain ridges.  Light valley winds.  Temperatures in the 10s & 20s, varying from single digits to around 10 degrees in sheltered upper elevation valleys to readings rising overnight into morning along mountain ridges ( to low-mid 30s on ridges within the 2000-3000 foot elevation zone ).  Wind chills from single digits & 10s on upper elevation ridges to the teens to lower 20s.

Mid-Morning Through Saturday Afternoon

Increasing clouds with lowering cloud bases over time.  Virga forming aloft with a chance for flurries to light snow developing, especially along and southwest from the High Knob Massif & Tennessee Valley Divide.  Windy & cold.  SSW-SW winds 15-25 mph, with higher gusts, at elevations below 2700 feet.  SW winds 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from upper 20s-low 30s at highest elevations to upper 30s to middle 40s, dropping with the onset of precipitation.  Wind chills in the 10s and 20s.  Dense fog developing at highest elevations.

Saturday Evening Into Sunday Morning

Chance of evening snow ( especially along-southwest of the High Knob Massif-Tennessee Valley Divide ) or mix giving way to rain.  Frozen forms possible in the SW upslope zone.  SSW-WSW winds 10-20 mph, with higher gusts on middle-upper elevation ridges, decreasing into morning.  Temps mainly from the lower 30s to around 40 degrees.  Areas of dense fog.

Sunday Afternoon

Mostly cloudy.  Chance of light showers or drizzle.  Milder.  Winds SSE to SSW at 5-15 mph.  Temperatures in the 40s to around 50 degrees.  Areas of fog, especially at highest elevations along mountain ridges.

Sunday Night Into Monday Morning

Mostly cloudy.  Chance for a light shower or drizzle.  Mild.  Winds SSE-SSW 5-15 mph along mountain ridges-plateaus below 2700 feet.  Winds SSW-SW 10-20 mph, with higher gusts, along upper elevation mountain ridges.  Widespread temperatures in the 40s to around 50 degrees.  Dense fog at highest elevations.

**The potential for a prolonged, harsh period of winter conditions is being monitored for the January 4-6 period, and beyond in time, with formation of high latitude blocking and a cross-polar flow from Siberia into North America.  Stay tuned for updates on this major shift into significant winter conditions in January 2017.

Weather Discussion ( More Nasty )

Reference My High Country Focus for a brief recap of 2016.

Saturday Afternoon Update

Flurries and light snow showers have occurred throughout the afternoon of New Year’s Eve Day across the High Knob Massif area of Norton-Wise ( even at low elevations in the downslope zone to Clintwood ).

Conditions have varied from beautiful mountain waves being visible to a reduction in visibility in light snow-flurries ( below ).

The atmosphere has been saturating from the top down, with the summit levels of the High Knob Massif now being obscured in freezing fog ( clouds ) amid flurries-light snow. A small accumulation has recovered roads.  Travel should be avoided on State Route 619, Routes 237, 238, and others in the upper elevations into this evening as frozen precip will continue at times ( fog will become persistent and lower in elevation to below the main crest lines by late evening ).

Winds are simply wicked in upper elevations, with gusts of 40-50+ mph being common.  The 5:15 PM temperature is 29 degrees on Eagle Knob of the High Knob Massif, with 30 at a little lower elevation on adjacent Black Mountain.

Wind have also, of course, been strong in Wise with Lonesome Pine Airport displaying its typical temp bias:

versus adjacent stations at the same elevation:

Surface temperatures from just below to just above freezing will continue into this evening within the upslope flow zone of the High Knob Massif area.

At all locations outside the highest elevations there remains a small temperature-dewpoint depression for evaporative cooling.  Temperatures aloft, above the high summits, should continue to warm to strengthen a low-level temperature inversion.  Strong wind gusts at locations below the elevation of Wise should begin decreasing, while gusty to ROARING winds will continue through the night in upper elevations.  Have a Safe & Happy New Year. 

Previous Discussion

Reference my 123016 Forecast page for details on recent snow.

Reference The High Knob Landform for views of December 2016.

Given wind and chilly conditions with developing virga to surface precipitation through New Year’s Eve and Morning, I have updated my forecast page to clean it up for these next upcoming weather conditions.

Winds are beginning to increase again at upper elevations, and this will continue into Saturday with mixing of higher speeds downward into middle and lower elevations with time ( at least until evaporative cooling begins ).

My main concern for the short-term will be the potential for some snow and frozen precipitation to develop Saturday PM & Saturday Evening, especially in the High Knob Landform corridor where SW air flow rises 1000 to 3000 vertical feet as it streams northeast from Tennessee.  The wind max that is shown above, over the Nation’s Heartland, will be along the Appalachians by New Year Eve Afternoon-Evening.

*Low-level cooling will be greater than models suggest into Saturday Evening, even as temperatures continue to warm aloft, so this threat must be monitored until wind direction’s change.

It is easy to see from this sounding forecast ( above ), that if the surface temperature & dewpoint are just a little closer together at levels downward from the summit of the High Knob Massif ( where orographic lifting occurs ) that the column will be saturated and sub-freezing through a relatively deep layer.  So my concern is a no brainer unless the model is completely out of whack, which is not as likely given current low dewpoint air ( to support cooling ).

Mild air for this time of year will then rule the mountain region from Sunday into Tuesday, with periods of rain, before conditions turn cold once again.

As always, please stay tuned for updates and have a Safe and Happy New Year.

Mountain Area Forecast ( Dec 29-Jan 1 )

ALERT For Snow Showers And Bursts Of Heavy Snow To 10:00 AM Friday.  Snow-Blowing Snow Will Reduce Visibility And Cause Travel To Become Hazardous In Locations Along & West-Northwest Of the High Knob Massif-Tennessee Valley Divide.  Less Snow And Lower Impacts Are Expected Lee Of The Mountains Into The Great Valley ( As Well As Below 1200-1500 Feet ).

A general 1″ to 3″ of snow are likely between Midnight and 10 AM Friday as very cold air aloft moves over the mountains.  This will combine with limited low-level moisture ( a marginal Great Lake event ) and strong WNW-NW winds to develop snow showers and bursts of heavy snow.  Due to very cold air aloft, some bursts may also occur leeward of the mountains in localized portions of the Clinch, Powell, Holston river valleys.

Thursday Night Into Mid-Morning Friday

Cloudy with snow showers & flurries developing.  Bursts of heavy snow.  Colder.  Snow accumulations of 1″-3″ along the upslope side of the mountains, with less than 1″ leeward of the mountains and at elevations below 1200-1500 feet in elevation.  WNW-NW winds 10-25 mph, with higher gusts.  Temps varying from low-mid 10s at the highest elevations to mid-upper 20s.  Wind chills in the single digits and 10s, except below zero ( especially in gusts ) at the highest elevations.  Rime formation in highest elevations.

Mid-Morning Friday Through Friday Afternoon

Snow showers & flurries ending.  Skies becoming partly cloudy.  Cold.  W-WNW winds 10-20 mph, with higher gusts.  Temperatures varying from upper 10s to lower 20s in upper elevations to the upper 20s to lower 30s.  Wind chills in the single digits and 10s, except below zero in stronger gusts at highest elevations.

Friday Night Into Saturday Morning

Mostly clear.  Cold.  Winds becoming SSW-SW at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges.  Light valley winds.  Temperatures in the 10s & 20s, varying from single digits to around 10 degrees within upper elevation valleys to readings rising overnight into morning on highest mountain ridges ( to around 32 F ).

Saturday Afternoon

Increasing clouds with lowering cloud bases over time.  Virga forming aloft with a chance for flurries to light snow developing late, especially along and southwest of the High Knob Massif & Tennessee Valley Divide.  Windy & cold.  SSW-SW winds 15-25 mph, with higher gusts, at elevations below 2700 feet.  SW winds 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from around freezing at highest elevations to upper 30s to middle 40s, dropping with onset of precipitation by late.  Wind chills in the 10s and 20s.

Saturday Evening Into Sunday Morning

Chance of evening snow ( especially along-southwest of the High Knob Massif-Tennessee Valley Divide ) or mix giving way to rain.  Freezing rain possible in some valleys.  SSW-WSW winds 10-20 mph, with higher gusts along middle-upper elevation ridges, decreasing into morning.  Temps mainly from low-mid 30s to around 40 degrees.

**The potential for a prolonged, harsh period of winter conditions is being monitored for the January 4-6 period, and beyond in time, with formation of high latitude blocking and a cross-polar flow from Siberia into North America.  Stay tuned for updates on this major shift into significant winter conditions in January 2017.

Weather Discussion ( Taste Of Winter )

Friday Snow Report ( December 30, 2016 )

Snow accumulations were widespread across Wise and Dickenson counties into Friday morning.  The most intense period came with a monster snow band that developed along the Virginia-Kentucky border toward 11:00 AM to Midnight, with near zero visibility at its peak and rapid sticking to all objects ( including roads ).

It was a wicked night in the High Knob Massif.  Joe & Darlene Fields measured 1″ of snow depth in High Chaparral by 10:30 to 11:00 PM, before the intense snow band hit.  Wind gusts of 30-40+ mph took wind chills down into single digits above and locally below zero.

Much of the snow in this view ( above ) fell horizontally or even upward in direction ( as you can tell by looking closely at lines made by larger flakes ).  WNW-NW winds of 20 to 40+ mph, of course, caused these conditions along with relatively dry, low water content snow.

Friday Morning Snow Reports

Head of Powell Valley: 1.5″
( 1-2″ AM Depths )

Nora 4 SSE NWS: 1.6″
( 2″ AM Depth )

Clintwood 1 W NWS: 2.0″
( 2″ AM Depth )

UVA-Wise NWS: 2.5″
( 2″ AM Depth )

Norton Water Plant: 2.5″
( 2″ AM Depth )

High Chaparral: 3.0″
( 3″ AM Depth )

Eagle Knob: 3.5″
*( Variable Depths )

*Best estimate of snowfall is 3.0″ to 4.0″ with highly variable   depths from near bare ground to 6″ or more in places.

Previous Discussion

Reference my 122916 Forecast for previous details.

A simply gorgeous sunset Thursday was observed above chilly, gusty conditions in advance of an approaching upper air disturbance featuring very cold air aloft.

Virga and a few flurries-sprinkles falling beneath puffy clouds signals what is upcoming by Midnight to 10 AM Friday as very cold air aloft ( 0 to -30 F below in the 10,000 to 18,000 foot zone ) moves across the mountains to help trigger snow showers, flurries, and some bursts of heavy snow ( squalls ).

Accumulations will primarily be limited to upslope zones with respect to W-NW flow.  The high resolution NAM 4 KM Model has the right idea but is skewed ( as almost always ) with placement and amounts due to terrain recognition problems and a flawed climatology database.

Great Lake connected flow will be marginal at best across the southern Appalachians.  The central Appalachians; however, from central-northern West Virginia northeastward, will be within true Lake moisture for a while as a Nor’easter rapidly intensifies along the New England Coast into Friday ( the negative tilted upper air trough hindering Lake moisture advection farther south into the southern Appalachians in this case ).

Looking ahead, following more wet and mild conditions to open up the New Year in early January, a radical change in the pattern is looking increasingly likely by the January 4-6 period and beyond in time.  High-latitude blocking centers near Greenland and Alaska will force cross-polar flow from snow laden Siberia into North America and the USA.

The potential for a harsh and prolonged period of winter is being monitored as this pattern takes shape, with perhaps a 2-3 week window of particularly bad conditions.  Stay tuned for later updates.

Mountain Area Forecast ( Dec 28-30 )

A Blast Of Cold Air Thursday Into Friday Morning Will Be Enhanced By Strong & Gusty W-NW Winds.  Upslope Snow Showers Are Expected Thursday Night Into Early Friday With Accumulations Varying From A Dusting Up To 3″ ( Mainly Windward Side Of The Mountains ).

Locations along and west to northwest of the High Knob Massif and Tennessee Valley Divide, as well as the TN-NC Border, will be most favored for accumulating snow.

Overnight Into Wednesday Morning

Mostly clear.  Seasonally cold.  Winds WNW-NW at 5-15 mph along mid-upper elevation mountain ridges.  Temperatures varying from 10s in colder mountain valleys to the 20s to lower 30s ( mildest on exposed mountain ridges ).  Areas of mainly river valley and lake fog & freezing fog.

Wednesday Afternoon

Sunny.  Light SSE-S winds mostly less than 10 mph below 2700 feet.  S-SW winds increasing to 5-15 mph, with higher gusts, on mountain ridges above 2700 feet.  Temps varying in the 40s to near 50 degrees.

Wednesday Night Into Thursday Morning

Becoming cloudy & windy.  Rain developing by midnight into the overnight.  A chance of thunder.  Rain ending as snow and/or sleet at highest elevations toward morning.  SSW-W winds 10-20 mph, with higher gusts, at elevations below 2700 feet.  Winds SW to WNW 15-25 mph, with higher gusts, along mountain ridges above 2700 ft.  Evening temps in the low 30s to around 40 degrees, then rising into early overnight before dropping again by morning.

Thursday Afternoon

Partly cloudy & windy.  Turning colder.  W to WNW winds 10-25 mph, with higher gusts.  Temperatures dropping into the mid-upper 20s to the mid-upper 30s ( coldest at highest elevations ).  Wind chills falling into the 10s and 20s, except single digits in gusts at highest elevations by late.

Thursday Night Into Friday Morning

Cloudy with snow showers & flurries developing.  Colder.  Snow accumulations of 1″-3″ along the upslope side of the mountains, with less than 1″ leeward of the mountains and at elevations below 1500 feet in elevation.  WNW-NW winds 10-25 mph, with higher gusts.  Temps varying from low-mid 10s at the highest elevations to mid-upper 20s.  Wind chills in the single digits and 10s, except below zero ( especially in gusts ) at the highest elevations.

*Another heavy precipitation event is now being watched for this weekend into early next week.  Precipitation may begin as snow or a mixture on Saturday ( December 31 ) before changing to all rain in all locations.  Heavy rain and strong rises on streams & rivers could occur early next week.  Stay tuned for later updates.   

**The potential for a prolonged, harsh period of winter conditions is being monitored for the January 4-6 period, and beyond in time, with formation of high latitude blocking and a cross-polar flow from Siberia into North America.  Stay tuned for updates on this major shift into significant winter conditions in January 2017.

Weather Discussion ( Big Changes )

Wednesday Evening Update

Evening temperature have fallen rapidly to around 30-35 degrees in mountain valleys, ahead of thickening clouds with a band of rain and some embedded thunder.  I have updated the forecast to account for this steep evening temperature drop and to add a chance of thunder with elevated instability above a cold boundary layer.

This will be adding more water to creeks that are already gushing with water pouring out of the High Knob Massif.

Temperatures should rise in valleys as strong and gusty winds mix throughout the vertical depth of the atmosphere with wind driven rains arriving in a couple more hours.

Previous Discussion

Much like the virtual switch flip from dryness to wetness that occurred in late November through December, another flip of the weather switch will occur in early January to kick off what I think will be a prolonged, harsh period of winter.

Meanwhile, rapid fire weather changes will continue into this weekend and early next week as a very active pattern continues to impact the mountain region.

The rise and drop of water levels on steep creeks draining the High Knob Massif during this past month tells the tale of wetness, with 7.00″ to 11.00″+ now having fallen just in December ( several inches more if adding late November ).

A total of 10.33″ were measured in the City of Norton, at base of the High Knob Massif, from November 28 to 9:00 AM December 27  ( with moderate-heavy rain falling at observation time Dec 27 ).

*Around 15.00″ or more of total precipitation has fallen across the head of Big Cherry Lake basin during the 1-month period between November 28 and December 27.  This NOT including substantial secondary moisture from RIME deposition on trees and fog drip from trees added to the watershed during this period.

A total water level rise of 12.5 vertical FEET has occurred on Big Cherry Lake in the High Knob Massif, with a significant overflow of its spillway causing a ROAR of whitewater on South Fork of the Powell River through South Fork Gorge.

Observe the dewpoint drop as dry air advection occurs into upper elevations ( from 2:45 AM to 4:35 AM ).  This dry air will enhance cold air drainage into deep valleys that decouple from boundary layer winds, especially in upper elevations, with mixing of this drier air into lower elevations after sunrise Wednesday.

Although winds remain brisk on high mountain ridges, the valleys are going calm and temperatures are really starting to drop as dewpoints are falling through the 10s at highest elevations to supply drier air for drainage into valleys.

A similar 900-800 MB dry air supported drop occurred in high valleys of the High Knob Massif on December 19-20.

The MIN in Wise reached 18 degrees, at the University Of Virginia’s official NWS Station, with 19 degrees at the official NWS station in Clintwood ( the Big Cherry Wetland Valley sensor being calibrated and checked by National Weather Service equipment in Clintwood prior to placement ).

A similar setting was observed during December 19-20 when the MIN temperature fell to 10 degrees in the Big Cherry Lake Wetland Valleys.  Although this was 6 degrees colder than in Burkes Garden and 11 degrees colder than recorded in Shady Valley, it illustrates the range that often occurs in our mountains that is never fully recognized.  The Big Cherry Wetland Valley sensor site likely not being in the coldest spot within high valleys of the massif.

While high mountain valleys in the Cumberland Mountains, especially those in the High Knob Massif, will tend to be the coldest by Wednesday morning, valleys in many locations will experience significant drops during the predawn to post-sunrise period ( especially where fog does not form ).

Sunny skies and dry air will promote a rapid temp rise in valleys Wednesday ahead of the next rapid fire weather change featuring another round of rain that gives way to arctic air and snow showers by Thursday Night.

Bombogenesis of low pressure along the New England coast will wrap most abundant moisture into windward slopes of the Appalachians from central-northern West Virginia northeastward, with 6-10″+ accumulating within  elevations above 3000 feet.

Meanwhile, the Mountain Empire only has a grazing shot with 1-3″ generally expected along windward slopes in the favored locations ( the model, as typical, not picking up on the High Knob Massif-Black Mountain area and its adjacent upslope snowbelt zone ).  Only flurries are likely leeward of the mountains, in much of the Tennessee Valley, with less than 1″ in general at elevations below 1500 feet in all sites.

This marks only the beginning of major weather changes upcoming as December passes into January.  You will want to stay tuned to MANY changes ahead.

Mountain Area Forecast ( Dec 26-28 )

Dense Fog Will Continue To Impact Portions Of The Area Into Monday Morning.  Fog Will Be Most Dense And Widespread In Valleys At Lower Elevations As Well As Along Upper Elevation Mountain Ridges.

Strong & Gusty S-SW Winds Will Impact The Mountain Area Monday Into Tuesday Morning ( Gusts of 30-40+ MPH ).  Mid-Upper Elevations Will Generally Have The Strongest Winds Outside Of Local Mountain Waves That May Reach Valley Floors In Favored Zones. 

A Squall Line Of Rain, With Embedded Thunderstorms, Will Be Possible By Tuesday Morning With Downpours Of Heavy Rainfall.

Overnight Into Monday Morning

Areas of dense fog ( especially in valleys at lower elevations and on upper elevation mountain ridges ).  SSE-SSW winds at 5-15 mph, with higher gusts, along mountain ridges and plateaus below 2700 feet.  S to SSW winds 15-25 mph, with higher gusts, along mountain ridges above 2700 feet.  Mild with temperatures in the 40s to low-mid 50s ( upper 30s to lower 40s in coolest mountain valleys ).

Monday Afternoon

Partly cloudy.  Unseasonably mild.  Windy.  SSE-SSW winds 10-20 mph, with higher gusts, below 2700 feet.  SSW to SW winds 15 to 25 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures varying from low-mid 50s in upper elevations to the low-mid 60s.

Monday Night Into Tuesday Morning

Showers with a chance for thunderstorms.  Locally heavy rainfall.  Windy.  SSW-SW winds 15-25 mph, with higher gusts on mountain ridges-plateaus below 2700 feet.  SW to WSW winds 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Unseasonably mild.  Temperatures widespread in the 50s to near 60 degrees.

Tuesday Afternoon

Skies becoming partly to mostly sunny.  Turning cooler.  Winds shifting W at 5-15 mph with higher gusts.  Temps dropping into the 40s by late, except into 30s at highest elevations.  Wind chills dropping into the 20s and 30s by late afternoon ( coldest at highest elevations ).

Tuesday Night Into Wednesday Morning

Mostly clear.  Seasonally cold.  Winds WNW-NW at 5-10 mph along mid-upper elevation mountain ridges.  Temperatures varying from 10s in colder mountain valleys to the 20s to lower 30s ( mildest on exposed mountain ridges ).

Much colder air will arrive Thursday into Friday with a chance for snow showers and flurries.  Some accumulations will be possible.  Stay tuned for updates on this wintry weather.

Weather Discussion ( Changeable )

Late Monday Evening Update

Strong and gusty SSW-SW winds are blowing across the area tonight in advance of an approaching cold front and line of showers with embedded thunderstorms.

Frequent wind gusts around 40 mph are being recorded along high mountain ridges, with 25 to 35 mph gusts common across middle elevation ridges & plateaus.  Locally strong wind gusts will occur in some valleys northeast of the high terrain.  Dense fog, with cap clouds, continues to obscure high mountain ridges along & to the southwest of the High Knob Massif and Tennessee Valley Divide.

Current inflow and wind streamlines are near the long-term mean climatology; although, models like the GFS do not recognize this and are forecasting little rainfall.

High resolution models that have better resolution are picking up on a downpour potential that will occur as the boundary nears during the predawn-morning period.

Very dry air advects ( is transported ) into the area later Tuesday, with clearing skies that sets the stage for frosty cold conditions into Wednesday morning when I expect a large vertical temperature spread between 10s in colder valleys and 20s to lower 30s ( mildest on exposed ridges ).

*High valleys in the High Knob Massif will fall to around 10 degrees if boundary layer winds can decouple, with strong drainage of cold air into the basins.

Previous Discussion

The History Of Christmases Past will be adding in 2016 with headlines for wet & foggy conditions, as abundant low-level moisture ruled the mountain landscape during the holiday.

Another significant rain event accompanied the foggy conditions with a widespread 1.00″ to 1.50″ being observed in counties along the Virginia-Kentucky border in the Cumberland Mountains.

December 2016 precipitation totals of 5.00″ to 10.00″ have been observed, with yet more coming to close out the month and year.

*Max precipitation totals occurring in the High Knob Massif where steep creeks have been gushing and mountain lakes overflowing with run-off.

While valleys have areas of dense fog, with light to calm winds, higher mountain ridges are engulfed in low clouds amid strong & gusty S-SSW winds.  Locations in between will experience the best visibility into early Monday.

Strong upsloping SSW-WSW winds will work to lower cloud bases again into Monday Night and Tuesday Morning as rain showers and a line of rain, with possible embedded thunder, develops across the mountain area.

The lower atmosphere is very moist and the air mass will be unseasonably mild for this time of year as the next wind driven front arrives by the predawn-morning hours of Tuesday.

A very photogenic storm system is sprawling across the USA at the current time, with a developing line of rain and thunderstorms.  The downpour potential with this should not be under-estimated as it arrives overnight into Tuesday morning, especially within favored SW upslope flow zones of the High Knob Landform and TN Valley Divide corridor.

A changing pattern is upcoming by late this week into the first week of January 2017 as blocking develops at higher latitudes in the vicinity of Greenland and Alaska, forcing negative dips in both the North Atlantic & Eastern Pacific oscillations = colder conditions with increased chances for wintry precipitation ( around or after the Jan 4-6 period ).

Stay tuned for updates on this changing pattern.

Mountain Area Forecast ( Dec 22-25 )

An ALERT For Strong S-SW Winds From Late Friday Into Christmas Eve Morning.  Wind Gusts of 30-50+ MPH Will Be Possible, Especially At Middle-Upper Elevations And With Any Mountain Waves.

The Potential For Heavy Rainfall, With Embedded Thunder Possible, Will Develop Into Christmas Eve Morning.  Abundant Low-Level Moisture Will Linger Behind The Heavier Rain Shield Into Christmas.

Overnight Into Thursday Morning

Partly-mostly cloudy.  Windy.  SW-WSW winds 10-20 mph, with higher gusts, on mid-upper elevation mountain ridges & plateaus.  Temps varying from 30s in the sheltered valleys to the 40s across exposed locations, then dropping into 30s toward morning in upper elevations ( to around freezing on highest peaks ).  Wind chills in the 30s and 20s, except 10s in gusts on high peaks toward morning.

Thursday Afternoon

Partly cloudy ( increasing clouds late ).  Winds shifting NW-N at 5-15 mph, with higher gusts.  Temperatures varying from low-mid 30s in upper elevations to the low-mid 40s, tending to drop during mid-late afternoon.  Wind chills in the 20s & 30s, except 10s at highest elevations.

Thursday Night Into Friday Morning

Mostly cloudy ( mid-high clouds ).  Northerly winds shifting E-SSE at 5-10 mph on mid-upper elevation mountain ridges.  Temperatures varying from upper 10s to lower 20s in the colder valleys to the upper 20s to lower 30s ( rising toward morning into the mid-upper 30s on high mountain ridges ).

Friday Afternoon

Mostly cloudy.  Windy.  SSE-SSW winds 10-20 mph, with higher gusts, especially across mid-upper elevation ridges and plateaus.  Temperatures mainly in the 40s to lower 50s.

Friday Night Into Christmas Eve Morning

Cloudy & windy.  Rain developing, with a chance for thunder, overnight into morning.  Locally heavy rainfall.  Winds SSE-SSW at 10-20 mph, with higher gusts, below 2700 feet.  Winds SSW-SW 20-35 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from upper 30s to mid-upper 40s.  Areas of fog.

Areas of fog will be across the mountain area Christmas Eve Day into Christmas Morning.  Widespread, dense fog will be likely at upper elevations in orographic clouds ( capping pilatus ).  Dense fog could also develop at other locations.  Remain alert for these conditions as abundant low-level moisture engulfs the area.

Christmas Eve Afternoon

Cloudy.  Heavy rain & possible thunder giving way to showers.  Areas of fog.  Gusty SW winds decreasing to 5-15 mph, with higher gusts, along mountain ridges below 2700 feet.  Winds SW-W at 10-20 mph on mountain ridges above 2700 feet.  Temperatures in the 40s to around 50 degrees.

Christmas Eve Into Christmas Morning

Cloudy ( abundant low-level moisture ).  A chance of showers-drizzle and areas of dense fog.  SW-W winds 5-10 mph, with higher gusts, on mid-upper elevation mountain ridges.  Seasonally mild with temps in the 40s to lower 50s.

Weather Discussion ( Wet Holiday )

Thursday Night Update

I have updated my forecast into the Christmas Holiday to increase wind speeds for late Friday into Saturday morning, with another strong low-level jet set to ROAR.

This also sets the stage for another rainfall enhancement episode with strong orographic forcing in the High Knob Massif-Black Mountain corridor.  Rain amounts of 1.00″ to 1.50″+ are looking likely in this area, to include the City of Norton ( within the massif’s lifting zone on SW air flow ).

Again it must be stressed that abundant low-level moisture lingers after the heavier rains pass, such that fog, drizzle and a few showers are likely to remain factors into at least mid-morning on Christmas day.

The Wettest Area In Virginia – Climate Notes

The pattern of low-level inflow into the mountain area has recently ( above ) been very close to long-term annual mean flow at the surface ( below ).

The long-term 925 MB flow ( below ), which is often near the elevation of Wise, has also been nearly identical to surface flow observed during this wet pattern.

 The current pattern reveals one factor ( of which there are many ) that makes the High Knob Massif area the wettest in Virginia, with a MEAN SW flow observed in the surface-925 MB layer ( the lowest portion of the atmosphere which is orographically lifted into the middle-upper elevations ).

In looking at air flow trajectories for any given location, it is very important in the Appalachians ( or any mountains ) to observe what lies UPstream.  In this case, a short and/or long-term SW flow can stream into the High Knob Massif area from the Gulf of Mexico without having to first cross high mountains upstream ( between the Gulf and massif ).  Much of the flow can actually stream up the open expanse of the Tennessee Valley to reach the High Knob Massif.

On the other hand, by dramatic contrast, a short and/or long-term SW flow reaching Mount Rogers-Whitetop must cross MANY high mountains upstream ( between the Gulf and Mount Rogers-Whitetop ).  In this case many repeated up-down slope motions have occurred to extract moisture from the air mass by the time it reaches what has always been assumed to be the wettest area in Virginia ( * ).

*Since Mount Rogers & Whitetop Mountain are the two highest in Virginia, most everyone assumed they were also the wettest given their higher elevations.  However, as has also been noted by other researchers ( such as Baker Perry and Charles Konrad ) elevation is only a single factor of MANY that collectively dictate the precip regime of any given area within the southern Appalachians.

The following are RAW data files containing precipitation observed by the AFWS ( IFLOWS ) System since September 30 ( at 7 AM ) for both Eagle Knob of the High Knob Massif and Whitetop Mountain.  The bulk of this falling since late November 2016.

Eagle Knob of High Knob Massif IFLOWS Since 093016

It should be noted that BOTH rain gauges have undercatches due to strong winds, with estimated values being on the order of 20-30% given direct comparison of such gauges to hand-measured NWS rain gauges ( i.e., we do a direct comparison between the IFLOWS at Big Cherry Dam and a NWS rain gauge, and during many past years I have compared the Eagle Knob IFLOWS to both NWS and other rain gauges ).  In other words, both of these gauges have likely caught only 70-80% of what has actually fallen ( these undercatches increase greatly for snow, but snowfall has been very limited to make this an excellent period for comparisons ).

Whitetop Mountain IFLOWS Since 093016

Even if the Whitetop Mountain undercatch is 30% versus 20% on Eagle Knob the difference holds ( actually increases a little ) between the two sites.  This is not a fluke, as per my observations during the past few decades this is intimately connected to air flow trajectories shown above and the up-stream air flow differences between each site and the Gulf of Mexico moisture source.

**Note I have never directly compared the Whitetop Mountain IFLOWS to a NWS rain gauge.  However, on Eagle Knob, I have measured differences of up to 60% or more on undercatches in rainfall during extreme wind events.  The IFLOWS loss on heavy and/or prolonged winter storm events can often be greater and more extreme than the most extreme wind driven rain events.

Apart from just looking at two wind swept peaks, I have complete confidence that the High Knob Massif area is the wettest in Virginia given many rain gauge records from a variety of elevations and exposures over long-time periods versus a similar set of sites in the Mount Rogers-Whitetop area of southwestern Virginia.

Previous Discussion & History Of Past Christmases

Rain and abundant low-level moisture will make the Christmas Eve to Christmas Morning period WET, NOT  white in 2016.

History Of Christmases Past ( 1963-2015 )

For lovers of snow, and memories passed, I have included a local history of Christmases dating back to 1963 when only Clintwood and Wise data was available.  I began adding in more information during the 1980s and 1990s when I started my climate research in the High Knob Massif area.

The above rime forming in the traditional manner via orographic forcing with upsloping across mid-upper elevations into December 19.  Freezing fog on December 20-21; however, formed via radiational cooling and near calm conditions at lower-middle elevations with an apparent combination of hoar frost and rime.  Hoar frost being by strict definition a deposition from gas to solid, while rime represents deposition from liquid to solid.  Supercooled vapor was present in both cases ( water can exist in a liquid state in clean air down to temperatures of -40 Celsius, or even lower in certain conditions, before it spontaneously begins to freeze ).

*A lingering inversion, the same basic one that said we would get very little snowfall with more mix and fog initially, has been responsible for this shift into lower elevations as drier air aloft mixed downward across higher elevations.

Abundant surface deposition in local parts of the Great Valley indicated an abundance of nucleation centers for crystal growth, likely from impurities in the air.  This may have supported both hoar frost and non-dynamic rime formation ( since rime formation is typically a dynamic process occurring with cold air advection and wind as air is physically forced to rise by the terrain in higher, mountainous locations of the Appalachians ).  Around 10 rime formation days have occurred in the High Knob Massif this month, with rime deposition on trees & vegetation being part of an important secondary moisture source ( along with fog drip from trees ) that adds substantially to the annual moisture budgets of locations like the lofty basins of Big Cherry Lake and High Knob Lake.

Some 18 of the past 28 years have featured snow cover in upper elevations of the great High Knob Massif, with the High Knob Lake basin being the area that I have used for general record keeping.  A white Christmas being one with at least 0.5″ of snow depth ( since we officially round snow depth to the nearest EVEN whole inch ).

As my brief history of the past reveals, there have been many wet Christmas Holiday periods since 1963.  This year adds another to the record, like in 2015, to keep whitewater rolling on steep creeks draining the High Knob Massif.

While models are not yet set on the exact axis of heaviest rainfall, it is clear that another moderate-heavy round of rain is set to develop across the Tennessee Valley into parts of the western Appalachian front range ( with past climo on this type of flow field supporting this basic solution ).

An abundance of low-level moisture is likely to engulf the area and linger again, partially being trapped beneath yet another low-level inversion.  So caution is advised for those traveling during the Holiday period.  After an autumn were rainfall was difficult to find, now moisture is becoming a nemesis as December has become very wet.  Yet a snow drought continues for now.  Could that end be in sight?  

Check back later for updates on what may be the end to our snow drought ( at least in the mountains ).

MAY YOUR HOLIDAY BE SAFE AND BLESSED.

Mountain Area Forecast ( Dec 18-20 )

Dense Freezing Fog Will Now Be The Main Factor Into Monday For Locations At Middle To Upper Elevations Along & North Of The High Knob Massif & Tennessee Valley Divide ( Above 2000-2500 Feet In Elevation )

*Visibility near zero at times, within this orographically generated upslope cloud deck of freezing fog, is expected.  Caution Is Advised.

An ALERT Continues For Strong Winds At Middle To Upper Elevations Into Sunday.  Wind Gusts Of 30-50+ MPH Will Continue Into The Predawn-Sunrise Period.

ALERT For Icing From Mid-Morning To Afternoon Hours On Sunday With Freezing Rain And Sleet In Addition To A Flash Freeze Up In Counties Along Either Side Of The Virginia-Kentucky Border.

**Vertical temperature profiles and wind fields indicate that a change to freezing rain then to sleet will be more likely than snow given that SW-WSW flow continues aloft in the 825-725 MB layer.  

This keeps an above freezing layer aloft which will change snow falling aloft into rain that will initially freeze, before changing into sleet as the cold air deepens in the vertical above the surface.  In addition, any wetness lingering from heavy morning rain will tend to freeze on porches, decks, and other surfaces amid a rapid temperature drop between mid-morning and early afternoon.

 With LUCK the bulk of precipitation will push east before temps drop below freezing; however, freezing fog, drizzle and a general freeze up remain likely.  Therefore I feel that an ALERT is the right call for everyone to become aware of these threats ( as it takes only a bit of icing to cause problems ).

Overnight Into Sunday Morning

Showers with a chance for thunderstorms.  Locally heavy rainfall.  ROARING Winds.  SSW-SW winds 15-25 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet.  Winds SSW-SW 20-35 mph with higher gusts along upper elevation mountain ridges.  Mild with temperatures steady or rising into the 50s to near 60 degrees.

Sunday Mid-Morning Into Sunday Afternoon

Rain mixing with and changing to freezing rain & sleet.  A period of snow possible.  Windy.  Turning sharply colder.  Low cloud bases-freezing fog at upper elevations dropping into mid elevations late.  SW winds shifting NW to N at 5-15 mph, with higher gusts.  Temps falling into the 30s and 20s, except into the upper 10s at highest elevations by late.  Wind chills dropping into 10s & 20s, except single digits at highest elevations by late.

Sunday Night Into Monday Mid-Morning

Low clouds with dense freezing fog across middle to upper elevations.  Chance for light snow, sleet or freezing drizzle.  Winds N-NE at 5-15 mph, with higher gusts.  Temperatures dropping into the mid 10s to mid 20s ( coldest at highest elevations ).  Winds chills in the single digits & 10s, except around or below 0 degrees in gusts on highest peaks.

Monday Mid-Morning Through Monday Afternoon

Cloudy to mostly cloudy below 3600 feet.  Partly to mostly sunny above 3600 feet.  Cold.  Winds N-NE at mostly less than 10 mph.  Temperatures varying from mid 20s to low 30s ( upper 20s to around 30 degrees Norton-Wise ).

Monday Night Into Tuesday Morning

Low clouds below 3600 feet in the evening, then low clouds mainly below 3000 feet by morning.  Partly cloudy above.  Cold.  Winds Light & variable with vertical elevation.  The temperatures varying in the 20s beneath clouds.  Temps rising to around or above freezing along upper elevation mountain ridges above 3300-3500 feet.

Weather Discussion ( Nasty Mess )

Monday Morning Update

I have updated my forecast for today to account for epic conditions in the vertical due to a strong inversion that I have highlighted now for a couple days.

Elevations below 3600 feet this morning are beneath a layer of clouds which marks the inversion, while conditions are mostly sunny ( with some high clouds ) above that level.

If vertical mixing increases enough it could mix out the low clouds into middle elevations ( with sunshine ) later today; however, it is likely that lower elevations will remain under the cloud deck.  Middle elevations also have a good chance of staying under the deck.  If so, then it will be a raw, cold day for those places within middle-lower elevations.

Right now, conditions are simply epic with at least a portion of the heavily rimed crest zone of the High Knob Massif like an island above a sea of clouds ( Black Mountain’s summit and the twin Beartown’s are also above the deck ).

Sunday Afternoon Update

The main focus now will be on freezing fog and a continued drop in temperatures tonight into Monday morning.  Light frozen forms of precipitation may continue to fall at times, with a warm layer aloft generating a strong inversion that will trap clouds well into Monday.

This is an orographically forced or generated fog so visibility will at times be near zero.  Extreme Caution is advised given that it is also a freezing fog with riming.

While Winter Wonderland Conditions will be developing into Monday, it will take a while before all the terrain will again become visible given this cloud trapping inversion aloft ( the same warm layer which kept snow flakes at a minimum, with freezing rain and sleet being the primary forms reported Sunday ).

Meanwhile, SLOW DOWN and Be Safe…Checking For Ice On Porches, Decks, Walks, Roads And Anything  You Need To Be Walking-Traveling On Outside.

Mid-Day Sunday Update

I have updated my forecast to allow for some snow mixing in or a period of light snow.  Temperatures have dropped into the upper 20s on High Knob as of 11:30 AM with some flakes of snow mixing with freezing rain-sleet.

Prior to freeze up the event total precipitation reached 1.84″ on Eagle Knob of the High Knob Massif.  That means more than 2.00″ given tremendous overnight winds = a lowered rain gauge catch.  

Peak wind gusts around 50 MPH were recorded in Wise, where sustained speeds as high as 35 MPH occurred.  Peak wind gusts of 50-70+ MPH were common at higher elevations.

Sleet is now the main precipitation type in Clintwood, so all forms of frozen will be possible into this afternoon.

While the bulk of precipitation will be moving east of the area, the main concern continues to be icing from temps dropping below freezing into this afternoon along with lowering clouds bases and formation of freezing fog at middle-upper elevations along and north to northwest of the High Knob Massif and Tennessee Valley Divide.  Light frozen forms of precipitation will continue to be possible.

Previous Discussion

Reference My 121716 Forecast Discussion For More Details.

For those who love snow I have bad news, especially if model forecast soundings in the vertical are on target.

Winter Wonderland Conditions are; however, likely to develop with freezing rain, sleet, freezing fog and, just perhaps, freezing drizzle all occurring.  This will be the most pronounced for those living in middle to upper elevations ( above 2000-2500 feet ), but all of this area should remain alert to these threats.

Models tend to handle temperatures aloft better than within the more complex realm of the planetary boundary layer; thus, more confidence can generally be put into forecast temperatures above the DIRECT frictional influence of terrain features.  They can still be in error, of course, if anything can lift the air enough to erase the warm layer ( in this case ).  A SW-WSW flow aloft is however a notorious set up for frozen forms at the surface other than snow.

The problem is the 825 to 725 mb layer, seen on these soundings by the RED TEMPERATURE LINE that crosses to the right ( above 32 F ) side of the dashed blue line which rises on an angle upward from the 0 ( 0 degree Celsius or 32 Fahrenheit point ) at the bottom.

Observe that occurs above the PBL ( boundary layer ) where low-level winds shift SW-WSW, as indicated by the wind barbs along the right side ( right of the RED-GREEN lines ).  So the model says that warmer air will continue to be transported aloft over cold air transport ( advection ) in low-levels.  That = A MESS.  The only good news being that heaviest precipitation should be east of the area by the time elevations below 3000 feet drop below freezing.

Arctic air will simply surge into the western slopes of the mountains Sunday but a lingering warm layer aloft, above the mountains, will cause snow falling aloft to melt into rain that first freezes below on surfaces near the ground before changing into sleet ( sleet will develop at low-mid elevations, especially, as cold air deepens vertically ).

It appears that the greatest potential for freezing rain and sleet of significance will be from the elevation of Wise upward; however, as many may understand from experience it takes only a little ice to cause problems.  So even if the bulk of precipitation is to the east there remains an icing threat from multiple factors.

Locations along and north to northwest of the High Knob Massif-Tennessee Valley Divide will also be at highest risk given that the terrain will tend to block and slow the incoming arctic air ( delaying it enough to help reduce the risk for locations lee of the front range into river valleys of the Clinch & Holston ).

*If the Virginia side of the border gets lucky ( the KY side being unlucky ) then maybe Black & Pine mountains might be able to slow down the cold air transport enough to allow most of the precipitation to push east.  Locations around and above 3000 feet; however, remain likely in this case to  have temperatures go below freezing before rain ends.  An abundance of lingering low-level moisture will support the formation of freezing fog at elevations above 2000-2500 ft, and freezing drizzle-sleet for all elevations, along & north to northwest of the High Knob Massif-TN Valley Divide from late Sunday into Monday ( so icy conditions to some extent look to be upcoming for most places in this area ).

Meanwhile, ROARING winds continue to be the story at mid to upper elevations along the Cumberland Mountains ahead of an approaching squall line and band of rain west of the Appalachians in Kentucky & Tennessee.

Many gusts over 50 mph ( to around 60 mph ) have been recorded at 2774 feet on Pine Mountain.  No forecasters should doubt that the high country above 3000 to over 4200 feet is not being blasted by this powerful SW flow which climatologically is the most windy and the most common trajectory in the Cumberland Mountains.

Winds are BLASTING the summit of the High Knob Massif with everything rockin’ tonight.  That was, of course, in my forecast and is no wonder given the potent SW wind field over top of the region ( below ).  It should not ever be forgot that hundreds of people live above 3000 feet in the massif, so it is not just trees and the mountain being blasted!

A total of 0.25″ to 0.50″+ ( 0.44″ highest rain gauge report but with significant undercatch in high winds ) has fallen so far across the High Knob Massif, with heavy rains and embedded thunderstorms likely by the predawn of Sunday.

Additional heavy precipitation amounts are likely into Sunday, especially as the strong SW winds help enhance amounts into lifting zones of the High Knob Massif and Black-Pine mountains.

The Storm Prediction Center maintains a marginal risk for severe thunderstorms up to the Virginia-Kentucky border, with the primary risk being wind damage.

Stay tuned to NOAA Weather Radio and your favorite media sources for possible watches-warnings and any other advisories that might be needed.

Temperatures across Kentucky at 3:25 AM Sunday:

Mountain Area Forecast ( Dec 16-18 )

Reference My Forecast For Today For The New Update

ALERT For A Major Storm System Impacting The Mountain Region Friday Night Into Sunday

Multiple Threats:

*Bitter COLD Air Will Continue To Be Felt Into Friday Morning With Single Digits & 10s

Bitter cold will continue to dominate the mountain area into Friday with single digits and 10s.  The coldest temps will occur in upper elevation mountain valleys and on ridges with 5 above to -5 below zero readings.

*HIGH Winds With ROARING S-SW Speeds Developing Friday Night Into Saturday

**Hurricane Force wind gusts ( 75 mph or higher ) will be possible at the High Knob Lookout on Saturday, especially during the pre-dawn to mid-morning period.  Any visitors should avoid going inside of the Lookout Tower where air funneling could blow someone over the walls ( it offers no protection ).

Gusty winds will begin developing across middle-upper elevations Friday and become STRONG Friday Night Into Saturday.  Gusts of 40-60+ mph will be possible by the predawn to mid-morning period of Saturday, especially within higher elevations.  Strong & gusty winds will continue into Saturday Night & Sunday.

*Mix-Frozen Possible At Onset Of Precipitation Into Saturday Morning – Especially In Colder Valleys And On Northern Slopes & North Slope Roadways Where Frozen Surfaces Will Take Longer To Thaw

Although strong winds and enhanced mixing will help air temperatures to rise above freezing across the area, some surfaces will remain frozen and/or partially frozen due to current bitter cold air and a limited above freezing time period at or above freezing prior to onset of precipitation.

*Heavy Rainfall & Embedded thunderstorms Will Be Possible In Advance Of Sunday Cold Air With Strong Rises Possible On Streams

 Strong SSW-SW upslope flow will again cause enhanced rainfall amounts along and southwest of the High Knob Massif and Tennessee Valley Divide.  Given precipitation totals of 7.00″ to 10.00″+ since November 28, and at least partially frozen ground, strong rises on streams will be likely in locations having heavy rainfall ( as will ponding within low-lying, poor drainage locations ).

*A Change To Frozen Precipitation & Snow Will Be Possible Sunday, With Potential For An Ice Up On Walkways, Porches-Decks, and Roads

Strong cold air transport back into the mountains behind a potent cold front Sunday will change rain into frozen forms that will transition into snow.  Accumulating snow will be possible, especially along and west-northwest of the High Knob Massif and Tennessee Valley Divide in counties along either side of the Virginia-Kentucky stateline.

Stay tuned to NOAA Weather Radio and your favorite media sources for updates on significant and rapidly changing weather conditions into this weekend.

Overnight Into Friday Morning

Mostly cloudy ( high clouds and a “ring around the moon” ).  Bitterly cold.  Light winds, except N-NW shifting S at 5-15 mph with a few higher gusts on upper elevation mountain ridges.  Temperatures in the single digits to lower 10s, except locally as cold as 5 above to -5 degrees below zero within valleys and on ridges at upper elevations ( before rising overnight into morning on the highest ridges ).

Friday Afternoon

Cloudy ( mid-high altitude clouds ).  Cold.  SSE-S winds increasing to 5-15 mph, with higher gusts, on mountain ridges & plateaus below 2700 feet.  S-SW winds increasing to 10-20 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures varying from mid-upper 20s to low-mid 30s ( coldest in upper elevations ).  Wind chills in the 10s & 20s ( coldest in upper elevations ).

Friday Night Into Saturday Morning

Cloudy.  Showers developing.  Thunder possible.  Caution for frozen surfaces at onset of precipitation.  Windy.  SSE-SSW winds 15-25 mph with higher gusts along mountain ridges-plateaus below 2700 feet.  Winds SSW to SW 20-35 mph, with higher gusts, on mountain ridges above 2700 ft.  Temps rising into the 30s & 40s ( wind chills in 20s & 30s ).

*Due to strong upslope flow the potential for low clouds and dense fog will need to be watched Saturday ( in addition to the showers ) from the High Knob Massif and Tennessee Valley Divide ( Norton-Wise area ) southwest, to contrast with higher cloud bases and/or periods of sunshine in downslope locations to the northeast where temps could be much milder in places like Pound & Clintwood.

Saturday Afternoon

Low clouds and fog from the High Knob Massif & Tennessee Valley Divide southwest.  Partly sunny to the northeast into northern Wise, Dickenson-Buchanan counties.  Chance of showers & drizzle in the upslope zone with chilly conditions.  Windy.  SSW-SW winds 10-20 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet.  Winds SSW-SW 20-35 mph with higher gusts along upper elevation ridges.  Temperatures varying from 40s to around 50 degrees in the upslope zone to the 50s to lower 60s in downslope locations.

*The highest temperatures may actually occur Saturday Night into the predawn of Sunday, especially if low clouds-fog develop on the strong upslope flow for the daylight hours of Saturday from Wise and Norton southwest.  Extremes in the area could vary from the upper 40s to around 50 degrees in upslope areas of the High Knob Landform to 60s in Pound, Clintwood, Haysi, and Grundy.

Saturday Night Into Predawn Of Sunday

Showers with a chance for thunderstorms.  Locally heavy rainfall.  Windy.  SSW-SW winds 15-25 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet.  Winds SSW-SW 20-35 mph with higher gusts along upper elevation mountain ridges.  Mild with temperatures rising into the 50s to near 60 degrees ( locally above 60 degrees in downslope locales of northern Wise, Dickenson-Buchanan counties around Pound, Clintwood, Haysi and Grundy ).

Sunday Morning Into Sunday Afternoon

Rain mixing with and changing to sleet & snow.  A chance for freezing rain.  Windy.  Turning much colder.  SW winds shifting NW to N at 10-20 mph, with higher gusts.  Temps falling into the 20s and 30s, except into the 10s at highest elevations by late.  Wind chills dropping into 10s & 20s, except single digits at highest elevations by late.

*A light to potentially moderate accumulation of snowfall will be possible during Sunday, especially along and west to northwest of the High Knob Massif and Tennessee Valley Divide.  Icing will also be possible, with amounts of ice versus snow dictating how much snow depth develops.  Stay tuned for later updates.

Weather Discussion ( Major Changes )

Saturday Afternoon Update

Roaring winds and strong SW upslope flow through the area I define as the High Knob Landform is doing its thing today, with low clouds, fog, light showers-drizzle and chilly temps versus locations adjacent to it with breaks in the overcast and temperatures of 55 to 60 degrees ( downsloping zone ).

I came to define the High Knob Landform ( geologic Powell Valley Anticline of the Cumberland Overthrust Block ) decades ago now partly due to this feature which I found to be an aspect of its long-term climatology.  An aspect of local weather that is predictable  as well, in advance.  During many winter seasons, of course, it can generate what has been termed as “freak” falls of snow; however, they are not freak at all and are part of this same pattern being experienced today ( just with colder air ).

Here it is more than just an inversion as is being experienced today upon the Tennessee Valley floor, within portions of the Tri-Cities.  

Here it is part of true orographic forcing that features deep, low-level cooling as air is lifted 3,000 vertical feet between northern Tennessee and the High Knob Massif.  It works to enhance mean annual precipitation amounts and is one factor critical to making the High Knob Massif area the wettest terrain in Virginia.

Rainfall totals today have topped 0.25″ in the High Knob Massif versus only a few hundreds in the downslope zone.

Differences from southwest to northeast along air flow illustrates the change in conditions from the zone where air is rising toward the High Knob Massif-Tennessee Valley Divide ( above ) to where air sinks downstream of the high terrain ( below ).  Similar milder conditions have been experienced today in Pound and Clintwood, as was forecast, amid the downsloping zone ( 57.3 degrees being the max reached so far in Clintwood ).

All temperatures will continue to warm through the atmosphere in advance of a strong cold front that will arrive by Sunday morning.  Winds will also continue to ROAR as they are doing outside my home right now!

*I do not understand why wind advisories were dropped, or never issued to begin with in some cases, amid the middle of such a very strong wind event.

Meanwhile, a Tornado Watch is now in effect across much of middle Kentucky and Tennessee and are next to Winter Weather Advisories ( something rarely seen ).

The most complicated part of this system is to come, as convection continues to develop ahead of a sharp temp plunge that will change heavy rain to frozen forms on Sunday.  The vertical temp profile is going to become absolutely critical to how much frozen precipitation actually falls and in what proportions.

Check back late tonight as I make updates to the forecast based upon the evolution of convection and new forecast model data.

Friday Evening Update

Winds are now ROARING across mountain ridges above 2700 feet in elevation, with sustained speeds around 30 mph and gusts of 40-50+ mph.

Sheltered valleys remain at or a little below freezing, with most other locations now easing above 32 degrees.

Light showers forming in the lift of the High Knob Massif have wet the ground and camera on Eagle Knob, as the lower atmosphere is beginning to moisten up.

Friday Afternoon Update

I have updated for a complete overcast with thickening of mid-high clouds across the region.  I have lowered my MAX temperatures, which already were the coldest forecast, by a little due to this with low-mid 30s at low-mid elevations.  Some places may not reach this until the end of this day.

SSW winds are increasing at high elevations, with much stronger speeds coming into Friday Night.  Waves are already forming in the turbulence aloft.

Note that it is the long wave lines, which go across this view from right to left, that are the orographic waves.  Other waves that are smaller looking have formed due to wind shear aloft with WNW flow streaming across developing S-SW low-level flow.

A strong temperature inversion will be developing into Saturday and may keep strong winds above many valleys until later mixing can break up the inversion.  That already has been factored into my forecast, as you note I talk about “mountain ridges-plateaus” when referring to winds.

The inversion formation shows up very well on this NAM 12 KM Model forecast sounding above Norton-Wise at 7 AM Saturday, with much milder temperatures at High Knob Massif summit levels versus low elevations.  Also note that wind speeds reach maximum intensity near the inversion top ( where red-green temperature-dewpoint lines bulge back toward the right ).

With little sun to heat up surfaces today, only what has been able to penetrate through clouds, this raises concern for frozen surface development overnight into Saturday Morning when everyone will need to take extra caution as precipitation develops – with valleys having a higher potential than high ridges.

Due to strong upslope flow and this inversion formation there will be a high potential for low clouds, damp and chilly conditions during most of Saturday in the upslope zone from the Tennessee Valley Divide ( e.g., Wise ) and High Knob Massif southwest toward Big Stone Gap into the Powell River basin of Lee County versus locations toward the northeast where low-level sinking ( inverse forcing ) will help warm up communities around Pound, Clintwood, Haysi and Grundy ( to note a few ), especially if strong mountain waves aid breakup of the inversion.

I have rearranged my Saturday forecast to account for this, breaking out Saturday Afternoon by itself to allow for temp warming in the SW upslope flow zone into Saturday Night and the predawn hours of Sunday.

Initial Discussion

Arctic and sub-tropical air masses will clash, literally right over top of the Mountain Empire, to generate WILD & LARGE changes in weather conditions through this weekend.

Turbulence ahead of an advancing arctic cold front interacted with the mountain terrain to generate a simply spectacular sunset above UVA-Wise on Thursday ( note the stacked lenticular clouds, at bottom of view, along edge of this wave filled cloud mass ).

An array of mostly high altitude clouds, with some mid-level clouds, will be the only thing to hold back temp drops overnight into Friday morning given an extremely dry air mass of true arctic origin ( and the fact that despite this time of year, and local climatology, there is no snow covering the ground to aid temperature drops ).

Such powerful winds, both near the surface and aloft, developing with this system are in direct response to huge temp changes, or gradients, forming between arctic and sub-tropical air masses.

Always a clear signal for a storm system of vigor, and one to be closely watched, is a 150-200+ MPH jet streak with a quad supporting upward vertical motion ( such as the Right Rear quadrant shown above ) moving over the mountains.  This will supply part of the dynamics aloft that will have to be closely followed to see how well they couple with low-level forcing generated by a strong push on the mountain terrain by a jet of powerful low-level winds.

*The most potent outcomes arise when upper-level dynamics and orographics couple together.  These settings can also be ones in which models struggle most to resolve mesoscale conditions.

The storm event is just coming into range of short-range, higher resolution models, so it is likely that some changes will occur in their output during the next 24-hours.

Given forecast wind speeds, by the European Model group, and now the short-range models, orographic forcing will become a bigger factor in the forecast than they are currently showing; although, you can see ( above ) how the NAM 4 KM tries to show major terrain features it has trouble resolving local topography.

Although thunderstorms are not expected to be a huge factor locally, the air will become unstable aloft initially and then vertically through the column from the surface to support embedded lightning & thunder.  A case where the currently cold atmosphere can be deceptive.  At the least, convective precipitation will be likely and this will be a factor in precipitation amounts to some extent.

The Drought Monitor does not always reflect local conditions in orographic areas, like the High Knob Massif, where with exception of Autumn 2016 the year has been seasonably wet.

While I understand farmers in the region have been hurt by a lack of summer-autumn rains, especially toward the VA-TN border, there is no longer a drought of any significance in the High Knob Massif area where the level of Big Cherry Lake has risen 9.8 vertical FEET this month to fill this major water supply up to its spillway.  Run-off along South Fork  of the Powell will be more significant for this event since the Dam will now not be holding back as much water.

It will be important to check back for updates and to keep alert for these rapid weather changes through this weekend.  While I tried to cover most of the bases, some forecast model twists & turns will undoubtedly arise as this major weather system develops.

Mountain Area Forecast ( Dec 13-15 )

ALERT FOR BITTER COLD CONDITIONS DEVELOPING WEDNESDAY NIGHT INTO THURSDAY WITH SINGLE DIGIT AND SUB-ZERO WIND CHILLS

Low Cloud Bases And Dense Fog Will Increase Across Mid To Upper Elevations Overnight Into Wednesday Morning, With Freezing Levels Dropping Into The Norton-Wise Area By Morning.  Caution Is Advised.

Overnight Into Mid-Morning Tuesday

Partly-mostly cloudy ( mainly high clouds following break up of low clouds-dense evening fog across high mtn ridges ).  Areas of fog possible in some lower elevation locations.  W-NW winds 5 to 15 mph shifting to SSE-SSW into morning.  Temperatures varying from 20s in colder valleys at upper elevations to the low-mid 30s, except rising temperatures overnight into morning along high mountain ridges.

Mid-Morning Through Tuesday Afternoon

Cloudy with light rain and showers developing.  Light SSE-SSW winds shifting SW by late.  Chilly with temperatures mostly in the 30s to low-mid 40s ( steady or falling into the 30s in upper elevations above 3000 feet ).

Tuesday Night Into Wednesday Morning

Cloudy with a chance for drizzle or high elevation light snow.  Cloud bases lowering with dense fog formation from around the elevation of Wise upward toward midnight into the morning.  Freezing fog developing by morning at locales above 2500 to 3000 feet.  NNW-NNE winds 5-10 mph, with higher gusts, along mid-upper elevation ridges-plateaus.  Temperatures varying from low-mid 20s to low-mid 30s, coldest in upper elevations.  Wind chills in the 10s and 20s.

Wednesday Afternoon

Mostly cloudy.  Low clouds possibly lingering across high elevation crestlines ( or lifting briefly ).  Seasonably cold.  N-NW winds mostly less than 10 mph.  Temps varying from upper 20s to lower 30s in upper elevations to the mid 30s to around 40 degrees.

Wednesday Night Into Thursday Morning

Partly to mostly cloudy.  Becoming windy and bitterly cold.  Chance of flurries and snow showers.  Light accumulations of very dry, fluffy snow possible along upslope side of the mountains.  WNW-NW winds 10-20 mph, with higher gusts.  Temperatures varying from to 0 to 5 degrees at highest elevations to the lower-middle 10s ( a little “milder” lee of the mountains into valleys of the Clinch, Powell, Holston ).  Wind chill factors in the single digits above and below zero, except -10 to -20 degrees below zero along upper elevation mountain ridges ( especially in the many gusts expected ).

Weather Discussion ( More Bitter Air )

Tuesday Night Update

I have updated the forecast to include more clouds through Wednesday into Wednesday night.  At the present time low cloud bases are engulfing locales above 3000 feet elevation, with very dense fog that is freezing at highest elevations.

As colder air arrives overnight, on northerly upslope flow, the threat for dense fog engulfing Wise and adjacent locales will increase with bases being in or just above the town.

Interesting clouds were observed above the High Knob Massif and Norton-Wise area during Tuesday ( above ) amid chilly showers.

As bitter air arrives Wednesday Night into Thursday there could be some snow showers; however, with no connection to Great Lake moisture sources any accumulations will be light ( as has been the recent trend ).

*Frozen precipitation types ( mainly sleet and/or freezing rain ) are being monitored at the onset of another storm system set to impact the region by late Friday Night-early Saturday before a change to all rain.  A change back to frozen types and/or snow will then be possible as cold air tries to catch deep moisture Sunday.  Significant rain will be possible in the middle.  Stay tuned for updates on this messy looking storm system. 

Previous Discussion

While more bitter air is on the way, the first topic is about another soaking rainfall with heavy 1.00″ to 2.00″ amounts in upslope locales of the High Knob Massif-Black Mountain corridor during Monday.

Whitewater creeks are again gushing with Big Stony Creek near the red alert level at 4 vertical feet of water depth.  A automated rain gauge at top of its 42 square mile watershed reported 1.40″ of rainfall; however, with 20-30 mph sustained winds and gusts of 40 to 50+ mph, there was at least a 20-30% undercatch on the gauge located at 4196 feet above sea level.

Caleb Ramsey measured 1.10″ of rainfall at the City of Norton Water Plant up to 9:00 AM Monday, with more rainfall after this time ( 3.76″ December / 52.33″ 2016 ).

The latest rainfall came between a couple of gorgeous sunsets, with mountain waves being illumnated late Sunday ( above ) as winds ROARED across the High Knob Massif in advance of the rains.  More waves were seen lingering after the rain event late Monday ( below ).

A much weaker system will develop more cold rain showers across the area Tuesday, with a wind shift to northerly into Tuesday Night-Wednesday Morning likely to lower cloud bases on upslope to engulf Wise and adjacent communities in dense fog ( by the Midnight-Sunrise period ).  Situations like this typically generate very dense fog that can be dangerous to those not expecting the low visibilities.

*If happening in the Tri-Cities this would generate a Dense Fog Advisory, but here it is nearly always overlooked and has simply become neglected despite covering hundreds of square miles in  the upslope advection zone ( orographically generated clouds ).

The main short-term feature will be another bitter hit of arctic cold air, with the MEAN of the 51-Member European Ensemble group forecasting temperature anomalies on the order of 20-30+ degrees Fahrenheit below average by early Thursday.  This will mean air temperatures near 0 degrees at the top of the high country, with 10s in “milder” locales at lower-middle elevations in the mountains.

Wind chill factors of 0 to -20 below zero are expected across upper elevations, especially amid the many gusts that will occur, with single digits to around 10 degrees at lower & middle elevations in the Cumberland Mountains.  CAUTION IS CERTAINLY ADVISED.

A dramatic temperature increase is expected as the next significant rain maker develops by this weekend, with a strong 850 MB low-level jet stream developing once again  to crank up orographics for yet more heavy rainfall.

Forecast vector wind flow is nearly ideal versus climatology for another heavy rainfall event within the High Knob Massif – Black Mountain corridor, with potential for more rain than just received.  This will need to be closely followed as it could push creeks hard enough to cause water problems.

While there could be some frozen on the edges, I can not stress enough yet again that the pattern is simply not what one would want for significant snowfall in the southern Appalachians.  In fact, it may be warming in the MEAN during the week before Christmas to continue what is currently the only drought going…a Snow Drought.

*Things can, of course, change quickly and this does not mean there will not be a White Christmas this year.  It also does not mean that there will not be significant snowfall this winter.  During the October-December 2015 period only a trace to 0.5″ accumulated in the mountain area.  Some 78″ followed during January-February atop the High Knob Massif, with 40-50″ in the Norton-Wise area.  So do not give up yet snow lovers!

Mountain Area Forecast ( Dec 10-12 )

Alert For Strong Winds Developing Mid-Late Sunday Afternoon Into Monday Morning With ROARING SSW- SW Speeds ( Widespread Gusts of 30-50+ mph )

Heavy Rainfall Will Also Develop Along The High Knob Landform And Upslope Locations Of The High Knob Massif And Tennessee Valley Divide Into Monday.  Rainfall Totals  Of 1.00″ to 2.00″ Are Likely, With Locally Higher Amounts.  Lesser 0.50″ to 1.00″ Totals Are Expected In Downslope Sites Across Northern Wise, Dickenson & Buchanan Counties ( e.g., Pound, Clintwood, Haysi, Grundy ).

Overnight Into Saturday Morning

Partly cloudy.  A few flurries in upslope locations of the High Knob Massif.  Bitter.  Winds SW-W at 5-10 mph, with some higher gusts, along mid-upper elevation mountain ridges.  Temperatures in the single digits to lower 10s.  Wind chills in the single digits along mountain ridges.

Saturday Afternoon

Partly to mostly sunny.  Cold.  Light and variable winds.  Temperatures varying from mid 20s to mid 30s ( coldest in upper elevations ).

Saturday Night Into Sunday Morning

Partly to mostly clear.  SSW-SW winds increasing to 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges.  Temperatures varying from 10s in mountain valleys to the 20s, except temperatures rising slowly overnight into morning along mid-upper elevation slopes-ridges to around freezing.  Wind chills in the 10s and 20s, except single digits in gusts at highest elevations.

Sunday Afternoon

Partly sunny ( high clouds ).  Increasing clouds late.  Becoming windy.  S-SSW winds 5-15 mph, with higher gusts, below 2700 feet.  SSW-SW winds 15-25 mph, with higher gusts, on mountain ridges above 2700 feet.  Temps varying from mid-upper 30s to the mid 40s.  Wind chills in the 10s and 20s along upper elevation mountain ridges.

Sunday Night Into Mid-Morning Monday

Increasing clouds.  Rain developing into the predawn and morning.  Downpours likely in upslope locations, with wind driven rain.  Winds SSW-SW 15-25 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet.  Winds SW 25-35 mph, with gusts over 50 mph in upper elevations.  Temperatures in the mid 30s to mid 40s, with strong late evening-overnight temp rises possible in downslope sites north-northeast of the High Knob Massif-Tennessee Valley Divide ( rising into mid-upper 40s to around 50 degrees ).

Mid-Morning Monday Into Monday Afternoon

Rain.  Heavy at times in the morning giving way to light rain and showers before diminishing to drizzle into the afternoon.  Low clouds with dense fog on highest ridges.  SW winds shifting W and decreasing.  Temperatures near steady or slowly falling in the 40s below 3000 feet.  Temps dropping into and/or through the 30s above 3000 feet.

*Strong rises on creeks draining the High Knob Massif and Black Mountain area ( along the VA-KY border ) will be possible Monday if heavy rainfall is realized, with efficient run-off on partially frozen ground in wake of prolonged arctic cold.

Weather Discussion ( Wet Pattern )

Some flakes of snow continue to fly along upslope sides of the High Knob Massif into this overnight, but only flurries.

A dusting up to around 0.5″-1″ accumulated into Friday morning, covering roads ( and riming trees at highest elevations ) for the first time this cold season.  Air temperatures Friday morning varied from bitter single digits at highest elevations ( with sub-zero wind chills ) to the lower 20s in more sheltered valleys of the lower terrain ( below 2000 feet ).

While the short-term drought, dryness, is now essentially history across the High Knob Massif with respect to total precipitation, a snow drought lingers.  Season to date snowfall totals are getting MUCH behind average.

Hundreds of Millions of Gallons of water have been gained by the Big Cherry Lake since November 30 via a total water level rise of 7.5 vertical feet ( with a slow rise currently continuing ).  The lake is now within a couple feet or so of being full, and I expect this next rainfall event to finish the job and likely generate overflow of the Dam’s spillway by the middle of next week.

Focus now shifts to the next weather system which develops a ROARING 60 knot 850 MB low-level jet up along the west side of the Appalachians by Sunday Night into Monday AM.

This forecast is supported by the European Model group which has 40 knot winds along the Virginia-Kentucky border by 7 PM Sunday, increasing into the night-Monday morning to around 60 knots.

These strong winds work to also crank up the orographics with moderate-heavy rainfall becoming likely along and southwest of the Tennessee Valley Divide and High Knob Massif into Monday.  Model rainfall predictions will be too low in this zone; although, rain gauges at higher elevations will struggle to catch this wind driven fall of rain.

Strong winds will cause significant rain gauge undercatches, especially in higher elevations, where rain will fall horizontally during a substantial portion of this upcoming event.

A stormy pattern continues through the extended, with a bounty of arctic air toward the north dropping into the USA; however, blocking from Greenland toward Alaska is not in the best position for significant snowfall over the southern Appalachians.  It could get close, and only a small change on any given event could be enough to allow the first significant snowfall to occur.  Local odds would be greatly increased if snow can get laid down to our north across the Ohio Valley ( which then would help nudge the baroclinic zone southward…and the mean storm track ).

Although the European shows a couple more shots of arctic air in the next 10 days, the ensemble MEAN illustrates that the southern Appalachians remain along the edge of the cold air ( in the mean ).

When an area is on the edge it is precarious, such that each event will have to be closely followed through the next 10 days to see if any tracks further south and/or amplifies enough to mix cold air with moisture over this region.

As snow cover increases to the north it will increase odds of getting a significant snowstorm developing south in time.  Until that happens; however, a snow drought is now the main precipitation anomaly in the massif area.

Some signs for a significant ( major ) storm are showing up out in the 7-10 day period, but heavy rain versus snow remains an open potential with rain currently being most favored.  Stay tuned for updates, as a major rainfall coming after December 12-13 and more cold air to freeze the ground would not be a good thing.