from LWX's 4am discussion - mix bag for most before the flip to a cold rain. places out west are probably in for a much longer icy event.
Warm advection precipitation starts to reach areas along I-64
and back toward Augusta and Highland counties by the afternoon
hours. Strong ascent atop the seasonably cold air mass will make
for a messy winter precipitation scenario by the evening into
overnight hours. A bulk of the initial activity falls on
Wednesday night with 925-850 mb temperatures rising above
freezing. Given sub-freezing air likely holding on at the
ground, a number of spots will see a freezing rain/sleet
mixture, particularly off to the west of I-95. It remains to be
seen if conditions are cold enough within the urban sprawl.
Significant icing is possible across the Shenandoah Valley,
Alleghenies, Blue Ridge, and their mountain valleys. However, a
great deal of uncertainty plagues the forecast which will help
dictate the timing and precipitation types/overall intensity.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
There remains subtle spread and inherent fluctuations between
different global guidance on a run to run basis. Expect fluctuations
in model guidance to continue, with guidance continuing to narrow
down the potential outcomes of storm track, intensity, and wintry
precip duration as the ULL trough/energy associated with this storm
becomes better sampled over the Pacific NW. Ensemble guidance
continues to support an ULL moving through the northern Ohio Valley
early Thursday and eventually stalling into the Great Lakes Friday
into Saturday before eventually shearing out by Sunday. How far
south the ULL tracks in the Ohio Valley in turn will influence
where/when a coastal low develops in the vicinity of the Mid
Atlantic in this Miller B setup.
Confidence continues to increase in a prolonged wintry event ongoing
to start the long term at 12Z Thursday. Given the anomalous high
pressure north of the region and surface ridge extending down the
spine of the Appalachians, wintry precipitation (all types) is
likely across the entire area Thursday morning. Given the forecast
850/925 mb temps, snow, sleet, freezing rain, and rain area all a
possible. Areas east of the Blue Ridge will change to all rain
quicker. Those locations west of the Blue Ridge, especially
sheltered valleys prone to hold onto the cold air longer, will see a
mixture of wintry precip through the day on Thursday into Thursday
night and possible Friday. Travel impacts are becoming increasingly
likely during this timeframe.
As the ULL moves offshore, there is the potential for a period of
upslope snow as several vorticity maxes move over the Appalachians,
starting Friday into Saturday/Saturday night. This will be highly
dependent on the aforementioned system and ULL pattern.
Strong winds are possible areawide on the backside of the low. Temps
will be below normal behind the system with high presure building in
late Sunday.
