Current Weather ALERTS

ALERT For Strong SSE-SSW Winds Developing Saturday With 30 to 50+ MPH Gusts

A strong pressure gradient in advance of a deepening Low and arctic cold front will drive strong SSE to SSW winds across the mountains Saturday.

ALERT For Heavy Rainfall Saturday With Strong Stream Level Rises Becoming Possible By Saturday Evening Into Early Hours Of Sunday

Heavy rainfall is expected to develop Saturday, with orographic enhancement along and SSE-SW of the High Knob Massif & Tennessee Valley Divide.

Due to very wet antecedent conditions and partially frozen ground ( especially at upper elevations where light snow cover persists ), strong rises will become possible to likely on streams by late Saturday. 

ALERT For A FLASH FREEZE By Predawn To Morning Hours Of Sunday, From Northwest To Southeast Across The Mountain Area.  Do NOT Drive.

Driving During This Time Period Is Discouraged. While Snow Accumulation Is Expected, The Main Concern Will Be Rapid Freeze-Up With A Layer Of Ice Forming Beneath Accumulating Snow.

A potent temperature plunge will quickly drop air temperatures below freezing by the predawn to morning hours of Sunday as snow begins to stick.

Since rain will fall up until the rain to snow change any VDOT pre-treatment will be washed away. 

Ground temperatures will also be near freezing on northern slopes and in complex terrain where very limited sunshine has been observed during the past five days or longer.

ALERT For Bitterly Cold Temperatures And Dangerous Wind Chills During Sunday Into Monday Morning

Cold, with a Flash Freeze, and NOT snow will be the component of this storm system with greatest impact on the local mountains.

Air temperatures in the 20s around sunrise Sunday will fall into and through the 10s at middle to lower elevations during the day.

Air temperatures in the 10s around sunrise Sunday at upper elevations will fall through the 10s into single digits during the day.

Wind chill factors will be much colder and will drop below zero at nearly all locations along and north to northwest of the High Knob Massif.

 

Mountain Area Forecast ( Jan 19-21 )

Overnight Into Saturday Morning

Mostly cloudy.  Becoming windy at higher elevations. SSE winds increasing to 8-18 mph, with higher gusts, on mountain ridges-exposed plateaus below 2700 feet. SSE-SSW winds increasing to 15-25 mph with higher gusts on mountain ridges above 2700 feet. 

Temperatures varying from low 30s to low 40s, tending to rise overnight into morning.  Low clouds with dense fog at highest elevations.  Wind chills in the 20s & 30s ( coldest at highest elevations ).

Saturday Morning Through The Afternoon

Cloudy with rain developing.  Rain will be heavy at times during the afternoon.  Chance of lightning and thunder.  Windy. SSE-S winds increasing to 15-25 mph, with higher gusts, below 2700 feet.  S-SW winds 20-35 mph, with higher gusts, above 2700 feet. 

Temperatures widespread in the 40s to around 50 degrees.  Low clouds with widespread dense fog at upper elevations.  Wind chills in the 30s to lower 40s, except 20s possible in strong gusts on high peaks.

Saturday Night Into Sunday Morning

Windy with rain changing to snow.  A rapid predawn temperature drop with FLASH Freezing and period of ROARING winds.  Winds shifting NW-N at 15-25 mph with gusts 40-50+ mph.  Temperatures plunging into lower-mid 10s to low-mid 20s in locations along and northwest-north of the High Knob Massif-Tennessee Valley Divide ( milder toward the southeast-south ).

Wind chills plunging into the single digits and 10s, except 0 to -10 degrees Fahrenheit below zero at highest elevations, into morning.  Low clouds with freezing fog at upper elevations, and possible into middle elevations.

   Sunday Morning Through The Afternoon

Snow showers and flurries.  Windy and bitterly cold. NW-N winds 10-20 mph, with higher gusts.  Temps falling into the 10s at middle-lower elevations along and northwest to north of the High Knob Massif and Tennessee Valley Divide, and through 10s into single digits at upper elevations.  Wind chills 0 to 10 degrees below 2700 feet and 0 to -15 degrees below zero above 2700-3000 feet.  Freezing fog with riming at the high elevations.  Dangerous wind chills higher elevations.

Sunday Night Into Monday Morning

Mostly cloudy with snow showers & flurries.  Bitterly cold ( Dangerous wind chills at higher elevations ).  Winds NW-N at 5-15 mph with higher gusts. 

Temperatures falling into single digits above and below zero.  Wind chills 0 to -10 degrees below zero at elevations under 2700 feet, and -10 to -25 degrees F below zero at elevations above 2700-3000 feet.

Snowfall Forecast_Sunday-Monday AM

A general 1″ to 3″ of snow is expected, with the following break-down being favored:

1″ to 2″ at elevations below 2500 feet

2″ to 4″ at elevations above 2500 feet

Target snowfall 2″ in Norton-Wise (+/-) 1″ error potential, suggesting 1″ to 3″ of snowfall will be possible.

Locally heavier amounts will be possible, with lesser amounts expected in downslope locations into river valleys of the Clinch, Powell and Holston basins.

Forecast Discussion ( Winter Begins )

While the southern Appalachians have already experienced a good bit of wintry conditions, I will predict that a look back at the 2018-19 season will show the true winter beginning this weekend.

Reference These Sections of The High Knob Landform

The reason will NOT be because of just the first big blast of arctic cold this weekend, but because of the hemispheric pattern that is taking shape.

The upcoming 6-10 day period on the MEAN of the 51-member European ensemble group is simply showing an outrageous setting, which if verified would set up some of the most severe winter conditions observed since at least February 2015.

As I have highlighted for a long time, recent major sudden stratospheric warming + Modoki ENSO + low Solar supports this type of pattern developing in the eastern USA.

To quickly see why it will be turning severe, one needs only to look at where the Polar Vortex lobe since the major stratospheric warming event has established itself over North America, and also understand that coupling has now occurred between the stratosphere and underlying troposphere.

Northern Hemisphere 10 MB Flow Field

In the short-term, the upcoming storm brings many concerns the first of which being heavy rainfall that will have local orographic enhancement not being fully depicted by the above model graphic.

A general 1.00″ to 2.00″ of rainfall is likely along the Cumberland Mountains.  Those living and driving in low-lying, flood prone locations, as well as creeks, should remain alert for water level rises.

Any thunderstorms which might form, or training lines of heavy rain, could generate more serious problems Saturday afternoon-evening.

Due to such a large pressure change, winds are going to be a notable factor during this event.  I expect at least one period of especially notable wind along and just behind the initial cold front which will mark a temperature plummet; although, many hours will experience strong winds, especially higher terrain locations in mid-upper elevations.

The temperature plunges from 46 to 22 degrees at the Wise gridpoint in just 5-hours, most of that occurring in 4 hours or less.  This is a major concern for FLASH or rapid freezing of anything covered by water.

So, please plan not to drive into Sunday Morning and be very careful about decks, porches, walks, etc…as an icy layer forms beneath snow ( and even in places where little snow falls ).

I have a couple problems with model forecasts.

The European Model group has consistently been colder than the American models at 850 MB, to suggest temperature drops will be stronger than have been predicted.  I have selected the high-resolution NAM which is closest to the surface reflection of what such temperatures would produce even though it does not predict 850 MB temperatures as cold as the European.

NOTE that the coldest air with this initial outbreak will be centered around 875-850 MB, with milder air above that level.  This continues a trend observed during the past 5-days, at least, with a notable low-level inversion layer centered around 875 MB. 

Low-level NW-N winds climatologically favors the strongest cooling to develop along and northward of the High Knob Massif, with a large temp difference developing between Clintwood-Norton-Wise versus the Tri-Cities into early afternoon Sunday ( larger than predicted by the above graphic ) due to the influences of orographics ( terrain changes ).

Another problem often observed is that bitter cold air coming off a snowpack to the north will have limited bare ground over which to modify, prior to reaching the mountains, as enough snow falls to cover the ground into the western slopes of the mountains.