021116 Forecast

My Forecast For Today ( February 11 )

ALERT For Bitterly Cold Temperatures-Wind Chills Continues Into Today.  This Pattern Will Continue Through This Weekend Into Next Week To Mark A Harsh Period Of Winter In The Appalachians.

Please Remain Alert For Hazardous Traveling Conditions As Well As Ice On Decks-Porches-Walks.

An Alert For Heavy Snow Squalls May Be Needed For Friday Night Into Saturday, With Significant Snow Accumulations Along And NW Of The High Knob Massif & The Tennessee Valley Divide that will tend to create very bad road conditions with plunging temps.
Bitterly cold conditions are expected Saturday into Sunday as part of the Polar Vortex gets stretched southward into the Great Lakes and NE USA ( in wake of major upper stratospheric warming ).

Potential of a Major Winter Storm Is Increasing for  February 15-16.  Please stay tuned for updates.

Overnight Into Thursday Morning

Mostly cloudy & bitter.  Light snow and snow showers.  Winds W-WNW 5-15 mph, with higher gusts, along middle elevation ridges & plateaus below 2700 ft.  WNW-NW winds 10-20 mph, with higher gusts, on upper elevation ridges.  Temperatures varying from 0 to 5 degrees at the highest elevations to lower 10s.  Wind chill factors varying from single digits to as cold as -10 to -20 below zero on upper elevation ridges.

Mid-Morning Through This Afternoon

Becoming mostly sunny.  Cold.  Light WNW-N winds at generally less than 10 mph.  Temperatures varying from middle to upper 10s at highest elevations to mid-upper 20s  ( a little milder in lower elevation valleys with little to no snow cover within portions of the Clinch, Powell, Holston river valleys toward the Tri-Cities ).

Tonight Into Friday Morning

Increasing clouds.  Winds becoming S-SW at 5-15 mph, with higher gusts, across mid-upper elevation mountain ridges and plateaus.  Temperatures in the 10s to low 20s, tending to rise at higher elevations into morning.

Some accumulating snow will be possible with a Clipper System during the day Friday, with heaviest snowfall likely to develop in NW Flow upslope locations Friday Night into Saturday.


Weather Discussion ( February 10-11 )

Reference my 021016 Forecast for details on snow accumulations which have varied from locally 1″ or less in portions of the Clinch and Powell river valleys up to 10-18″ across windward slopes and crest lines of the High Knob Massif.

The air is so cold that as long as any lower clouds are along upslope locations, especially windward sides of the great High Knob Massif, some flakes of snow will continue ( as have been observed this evening on Eagle Knob ).

High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise

Snow and low clouds broke just in time for sunset to be revealed in its glorious beauty above the snow covered mountain landscape.

High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise

Wednesday afternoon temperatures were bitter cold with widespread 10s across middle elevations and single digits amid upper elevations ( above 3000 feet ).  A few lower elevation valleys managed to break above 20 degrees.

Nora 4 SSE - Official National Weather Service
Nora 4 SSE – Official National Weather Service Site In Middle Elevations
Wind chills as cold as -10 below zero occurred at Nora 4 SSE.

Relative humidity remained high along windward slopes all day, with continuous light snow and heavier snow showers in localized hit-miss fashion ( for the snow showers ).

Black Mountain MesoNET
Black Mountain MesoNET – Observations During Past 24-Hours

 Temperatures have actually been rising a little at highest elevations during the evening, but wind gusts have been increasing to generate chill factors between -15 and -20 degrees below zero along high mountain crest lines.

Black Mountain MesoNET
Black Mountain MesoNET Up To 12:15 AM – February 11, 2016

Generally, it appears that clouds will remain abundant along the upslope side of the mountains into this morning before finally giving way to clearing.

JKL Doppler At 1:47 AM
JKL Doppler At 1:47 AM on Thursday – February 11, 2016

In fact, more light snow accumulations are likely along windward facing slopes within upper elevations of the  High Knob Massif overnight, with flurries and light snow amid lower-middle elevations having a chance to slicken a few roads that have cleared in Wise-Dickenson counties.

It will take very little to do that given current air temperatures.
European Model 850 MB TEMP & Surface Analysis
European Model 850 MB TEMP & Surface Analysis – 7 PM February 10, 2016

The coldest air with this first arctic blast ( the axis of the 850 MB thermal MIN ) will begin to shift northeast of the mountain area by morning.

European Model 150 MB Analysis
European Model 150 MB Forecast at 7 AM on February 12, 2016

Focus now shifts to both a temporary stretching and southward extension of the Polar Vortex ( above ) and a very active upstream array of energy across the Pacific Ocean.

Eastern Pacific Water Vapor
Eastern Pacific Water Vapor Image At 12:01 AM – February 11, 2016

 Following a break today the pattern quickly turns active again with a Clipper System diving down into the base of another deepening USA trough Friday.

Light snow will spread across the region during the day Friday, in advance of another blast of bitter air arriving Friday Night into Saturday.  Along with this a Great Lake connected NW Flow period will crank up intense snow squalls along the upslope side of the mountains Friday Night into Saturday along-behind an Arctic Front.

My preliminary projection is for 1″ to 3″ of snow across the area in general, with 3″ to 6″ in favored upslope locations along and north  of the High Knob Massif & Tennessee Valley Divide ( generally the most being in upper elevations of the massif above 3000 feet ).  Stay tuned as I will make an actual forecast tomorrow night.
ECMWF Mean Sea Level Pressure Anomaly Forecast
ECMWF Ensemble Mean Sea Level Pressure Anomaly Forecast – 7 AM Monday

Models will require a couple more days before the details of a potentially major early week storm system can be figured out, with energy for this system still in the Pacific Ocean.

There is plenty enough ensemble support in the 51-Member European Model cluster to warrant that this will be one to closely watch and flag now for the potential of significant wintry precipitation.  Stay tuned.

Make it a great Thursday.