021317 Forecast

Mountain Area Forecast ( Feb 13-15 )

An ALERT For Heavy, Wet Snow Is In Effect From  10:00 PM Tuesday Until 10:00 AM Wednesday For Elevations Above 2500-3000 Feet

Rain and wet snow, with mostly snow above 3000 feet in elevation, is expected to develop across the area late Tuesday Night into Wednesday.  Significant amounts of snow will be possible for upper elevations, above 3000 feet, with light-moderate snowfall amounts at elevations above 2500 feet.
Little to no snow accumulation is expected below 2000 feet.
NW winds will continue to gust 30-40+ mph at mid-upper elevations overnight into early Monday, especially on the mountain ridges, with dropping wind chill values as air temperatures continue dropping.  Caution is advised.

Overnight Into Monday Morning

Partly cloudy.  Windy.  NW winds 10-20 mph, with higher gusts, especially on mid-upper elevation mountain ridges and plateaus.  Temperatures dropping into the 20s, varying from near 20 degrees highest elevations to near 30 degrees. Wind chills in the 10s and 20s, except single digits in gusts along upper elevation mountain ridges.

Monday Afternoon

Mostly sunny.  Some increasing high clouds by mid-late afternoon.  NW winds diminishing to 5-10 mph, with a few higher gusts along mountain ridges.  Temperatures varying from low-mid 30s in upper elevations to the low-mid 40s.

Monday Night Into Tuesday Morning

Increasing mid-high altitude clouds.  Light winds shifting WSW to WNW at 5-10 mph, with higher gusts, along upper elevation mountain ridges.  A vertical temp spread from 10s to middle 20s in mountain valleys versus 30s along exposed middle to upper elevation mountain ridges-plateaus.

Tuesday Afternoon

Partly to mostly cloudy.  SW winds increasing to 5-15 mph, with some higher gusts.  Temperatures varying from 30s in upper elevations to the mid 40s to around 50 degrees at the lower-middle elevations.  Wind chills in the 20s and 30s on gusty mid-upper elevation mountain ridges.

Tuesday Night Into Mid-Morning Wednesday

Rain, sleet & snow developing.  Heavy, wet snow possible, especially at elevations above 2500-3000 feet.  SW winds shifting W-NW at 5-15 mph, with higher gusts.  Temps from the 20s in upper elevations to the low-mid 30s.

Snowfall Forecast: 10 PM Tuesday – 10 AM Wednesday

A general 3″ to 5″ of snow is expected above 3000 feet in the High Knob Massif to Black Mountain corridor, with locally higher amounts to around 6″ possible in the massif ( this also includes upper elevations of Clinch Mountain and the Whitetop-Mount Rogers area in southwestern Virginia ).

Target Snowfall of 2″ In Wise (+/-) 1″ Error Potential.  This suggests the potential for 1″ to 3″ of snow at elevations below 3000 feet in the middle elevation zone.  Little to no snow is now expected to accumulate at elevations below 2000 ( within lower elevations ).

A general 1″ to 2″ is expected above 2200 feet, with rain & snow and little to no accumulation expected at elevations below 2000 feet.

*While nearly all snow is expected above 3000 feet elevation, the ultimate amounts observed across middle elevations will be determined by how low the level of sticking snow drops overnight into Wednesday morning.


Weather Discussion ( To Snow Or Not )

Tuesday Afternoon Update

An elevation biased snow event will be developing Tuesday Night into Wednesday Morning.  Significant differences in amounts are expected in the vertical, varying from little to no accumulation below 2000 feet to as much as 3″-6″ above 3000 feet in the High Knob Massif-Black Mountain area.

High Knob Massif Webcam – University Of Virginia’s College At Wise
A mackerel sky above UVA-Wise is a sign of changing weather conditions upcoming tonight into Wednesday Morning.

Wet, slushy snow amounts of 1-2″ will be possible down to around the elevations of Norton-Wise, and adjacent ridge communities across central-southern Wise and Dickenson counties ( mainly during the overnight-predawn period ).

Hazardous travel conditions are expected in locations that are impacted by a fall of wet snow ( snow to water ratios are expected to be around 10:1 during this event ).

Black Mountain Mesonet

Early afternoon temperatures in the upper 30s ( 38 degrees on Black Mountain, hovering in the 36 to 37 degree range on Eagle Knob of the High Knob Massif ) and dewpoints in the 10s indicates significant evaporative cooloing will produce all snow at highest elevations, with a mixture of rain-snow and sleet possible during this fast hitting event at lower and middle elevations.


Previous Discussion

Sunday ( February 12 ) featured the warmest temperatures since mid-November, followed by a strong downward turn that will continue into this Monday morning.

Reference my 021017 Forecast Discussion to review ROARing winds that should have produced a High Wind Warning ( the Morristown NWSFO did issue a Wind Advisory ).

The main focus now shifts to a mid-week system that has now been “outlooked” for a long time by models.  While a major winter storm has never been expected for the area, this system can not be written off as a non-accumulation event with potential of significant snow remaining for February 15 ( especially above 2000-3000 feet ).

European Model Analyzed 500 MB Height Anomalies On Sunday ( Feb 12 )
Part of the energy with this southern energy will hold back over Mexico, as the remainder passes across the Mountain Empire to form another phasing event ( the 3rd in a series ) with northern stream energy over New England.  Bombogenesis looks to again occur with an intense surface low lifting toward Nova Scotia.
An east-based -NAO ( negative North Atlantic Oscillation ) is currently in place but will feature propagating 500 MB heights into Europe from Greenland ( i.e., a transitory or moving block featuring anomalously high 500 MB heights ) as this next storm develops and bombs near Newfoundland-Nova Scotia.
NAM 4 KM Model Total Snowfall Forecast To 7:00 AM Wednesday ( Feb 15 )

With the event just now coming into view of high resolution models, new runs through Monday into Tuesday will need to be closely followed.  Currently ( as of 1:30 AM Monday ) the NAM 4 KM, GFS Model and the European Model are all in rather close agreement on several inches or more of snow accumulation at higher elevations in southwest Virginia.

The 00z Monday ( 7 PM Sunday ) run of the European 9 KM Model is forecasting 2″ to 5″ of snow across higher elevations in southwest Virginia.  The new European still has trouble fully resolving local terrain, so snow amounts and levels are not set.  These are only preliminary numbers that will likely change in the next 24 hours.
GFS Model Total Snowfall Forecast To 7:00 AM Thursday ( February 16, 2017 )

I will update again by late Monday Night-early Tuesday.

The Bottom Line…A southern stream system passing across the Mountain Empire into Wednesday ( Feb 15 ) will bring the potential of accumulating snow.

It remains too early yet to tell about snow amounts; although, the preliminary view suggests that heaviest snowfall totals will likely occur at elevations around and above 2000 to 2500 feet.  Several inches or more is an initial guess by models.  Stay tuned for updates.

European 51-Member Ensemble MEAN 500 MB Height Anomalies: Days 6 to 10

The UP and DOWN pattern of this winter season will roll onward, with another significant warm period expected by this weekend into next week…followed, it appears, by yet another big downward turn and more winter precipitation potential by the middle or end of next week ( i.e., during final days of February 2017 ).