031517 Forecast

Mountain Area Forecast ( March 15-17 )

ALERT For Strong SW Winds At Higher Elevations Above 2500 To 3000 Feet During Friday Night

A combination of rainfall and snow melt will make strong rises on creeks draining the High Knob Massif & Black Mountain possible by Saturday.  Caution Is Advised.

Wednesday Night Into Thursday Morning

Mostly cloudy through the evening then becoming partly to mostly clear.  A chance for snow flurries, especially along the upslope side of the High Knob Massif.  Bitter cold.  NW winds 5-15 mph, with higher gusts, below 2700 feet.  NW winds 10-20 mph, with higher gusts, above 2700 feet.  Temperatures dropping into single digits and 10s, coldest at upper elevations.  Wind chills from 0 to -10 below at highest elevations to single digits and 10s.

Thursday Afternoon

Mostly sunny.  Cold.  WNW winds 5-10 mph, with some higher gusts.  Temperatures varying from low-mid 20s at highest elevations to the mid-upper 30s ( milder at lower elevations with no snow cover ).

Thursday Night Into Friday Morning

Clear early then increasing mid-high clouds.  Winds shifting SW-W at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges.  Temperatures varying from the single digits and 10s in valleys to rising readings through the 20s to lower 30s on exposed middle-upper elevation mountain ridges-plateaus ( coldest temps within high valleys of the snow covered High Knob Massif ).

A chance for brief frozen types, in colder valleys as well as at highest elevations, will exist during mid-morning into noon.
Due to interaction with cold, snow-covered ground, fog could become extremely dense at upper elevations in the High Knob Massif later Friday into Friday Night.  Caution is advised.

Friday Afternoon

Cloudy & windy.  Showers developing with a chance for elevated convection.  Downpours becoming possible late.  SSW-SW winds 10-20 mph, with higher gusts, at elevations below 2700 feet.  Winds SW to WSW 15-25 mph, with higher gusts, along mountain ridges above 2700 feet.  Chilly with temps becoming widespread in the 30s to lower 40s.  Dense fog forming with orographic clouds capping upper elevations of the High Knob Massif.

Friday Night Into Saturday Morning

Showers with a chance of thunder.  Downpours likely.  Wind driven rain upper elevations in the High Knob Massif.  SW winds 10-20 mph, with higher gusts, on mountain ridges & plateaus below 2700 feet ( decreasing some by morning ).  Winds SW to WSW 20-30 mph, with higher gusts, along mountain ridges above 2700 ft.  Temps widespread in the mid-upper 30s to middle 40s.  Wind chills in the 20s & 30s, coldest at highest elevations.  Areas of dense fog, widespread at upper elevations.

Snow showers & flurries will be likely Saturday Night into Sunday Morning.  Accumulations of up to 1″ will be possible above 3000 ft.  Low clouds with dense, freezing fog ( riming ) will occur at highest elevations.  Cloud bases will drop into the early morning hours of Sunday toward 3000 feet ( or locally lower ) before skies break.


Weather Discussion ( Recap Of Storm )

A recap of the winter storm, which was not forecast by the MRX NWSFO to strike Wise County ( pitiful job ) finds that it ranks as either a tie for the heaviest or as the heaviest event of this 2016-17 Winter Season at elevations above 3000 feet within the sprawling High Knob Massif of Wise County and northern Scott County in southwestern Virginia.**

March 13-15 Storm Snowfall-Depths
( Mean Ground Depth AM March 15 )

Clintwood 1 W – Elevation 1560 feet
2.0″ Snowfall ( 1″ ground depth )

Nora 4 SSE – Elevation 2650 feet
3.1″ Snowfall ( 2″ ground depth )

City of Norton WP – Elevation 2342 feet
3.3″ Snowfall ( 2″ ground depth )

UVA-Wise – Elevation 2550 feet
4.0″ Snowfall ( 3″ ground depth )

High Chaparral of High Knob Massif
7.0″ Snowfall ( 6″ ground depth )

Eagle Knob of High Knob Massif
10.0″ Snowfall ( 6-12″+ depths )

**Where hundreds of families live and so many more work, travel and enjoy an array of outdoor recreation.

Accumulating snow was widespread along the upslope side of the mountains, NW of the Cumberland-Allegheny Front, and spotty in nature ( as expected ) lee of the mountains into the Clinch, Powell, and Holston river valleys.

Eagle Knob of High Knob Massif At 10:18 AM March 15 ( 5 degrees with -10 to -20 WCF )
This event produced all snow at highest elevations in the massif with 5″ of accumulation into Tuesday morning ( during the wet snowfall phase ) and at least 5″ more into Wednesday morning   during the dry snowfall phase ).
If anything this 10.0″ storm snowfall total is low, as many factors work together at this point in the season to reduce the snow depth which generally was in the 6″-12″+ range ( becoming wind blown into morning hours of March 15 ).
High Chaparral of High Knob Massif At 10:45 AM on March 15, 2017

Dropping downward to 3300 feet a mean snow depth of 6″ was measured in the High Chaparral community by veteran snow observes Joe & Darlene Fields on Wednesday morning.  The total snowfall at this elevation was at least 7.0″ and breaks down by time periods as follows:

High Chaparral of High Knob Massif
Elevation 3300 feet

*7:00 AM Tuesday: 2″ Snow Depth

5:00 PM Tuesday: 4″ Snow Depth

10:00 AM Wednesday: 6″ Snow Depth

*General 4″ to 5″ snow depths at the summit level
Snowfall into Tuesday morning ( March 14 ) was wet and fell with minimal northerly winds.  Some melting and settlement occurred even within these upper elevations.  It was essentially all snow at the summit level with a period of rain and rain-snow mix to wet snow in High Chaparral.
Generally no sticking occurred below 1500 to 2000 feet elevation into Tuesday morning.  During the day, frequent snow showers and flurries began sticking at all elevations along the upslope side of the mountains; however, I observed sticking-melting several times in Clintwood as some sunshine ( mainly insolation through clouds ) occurred  between showers.
The worst widespread driving conditions developed across Wise-Dickenson counties between sunset Tuesday and sunrise Wednesday when very cold air aloft combined with Great Lake moisture and upsloping NW winds to generate widespread snow showers-flurries and snow squalls.
High Chaparral of High Knob Massif At 10:46 AM – March 15, 2017

The January 27-30 winter storm also produced 7.0″ of total snowfall in High Chaparral to tie this event for the heaviest of the 2016-17 Winter Season ( to date ).  This has, of course, been an OFF winter season with respect to snow but still this was a significant event for upper elevations.

Mean Ground Depth In High Chaparral of High Knob Massif – Morning March 15, 2017
A combination of wet snow, then dry snow and riming produced winter wonderland conditions.
Beauty In High Chaparral of High Knob Massif At 10:46 AM – March 15, 2017

Roads became so slick that even UVA-Wise closed classes for Wednesday, along with Wise County and Dickenson County where it is more common for classes to be closed.

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

The other aspect neglected by official forecasts has been simply brutal wind chills for this time of year at higher elevations ( from Norton-Wise upward in elevation ).

High Knob Massif Webcam – University Of Virginia’s College At Wise ( Blowing Snow )
Wind chills have been in the 0 to -20 below zero range, with locally even colder values no doubt at wind prone highest locations in the High Knob Massif.
Black Mountain Mesonet – Sample Hour Ending At 9:20 AM – March 15, 2017
Black Mountain Mesonet – Sample Hour Ending At 2:15 PM – March 15, 2017

The main aspect I missed in the forecast into Wednesday was the sky coverage, with mostly cloudy skies holding tough amid continuation of a Great Lake moisture plume that continued to produce PM flurries on High Knob.

Reference My 031317 Forecast and Discussion for details.
NASA Visible Image At 3:00 PM on March 15, 2017
A recap of models finds that the GFS did terrible on this event for the local mountains.  The European picked up on the wet snowfall phase but underestimated amounts at higher elevations.  It missed the dry, Great Lake moisture snowfall phase completely.
All models under-estimated the moisture advection from the Great Lakes which generated the significant snowfall during Tuesday night into Wednesday morning, with the NAM 3-4 KM picking up on the moisture plumes but under-estimating snow amounts at all elevations along the upslope side of the terrain.
Past climatology of similar events ( such as the cited March 2013 Miller B-A to bomb scenario ) once again proved to be a powerful guide to what this winter storm produced along the western front range of the mountains.