Blacksburg NWS has good discussion text
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 300 PM EST Thursday...
Cold high pressure will continue to move east across the Ohio
Valley to the Mid Atlantic region Saturday evening. Overnight
Saturday into Sunday morning, cold dry air will wedge south into
the Carolinas and southern Appalachian Mountains. Meanwhile
across the south, an upper level low over the Mid West will push
a surface low east across the Gulf States. Bulk of Gulf and
Atlantic moisture with the surface low will stay south of the
area through Saturday evening. Snow will edge northward Saturday
night, starting across the High Country of North Carolina then
spreading across the entire area Sunday morning.
Sunday morning the upper level low tracks over Tennessee and
Kentucky increasing moisture transport over the wedge. The
combination of upslope flow, strong warm air advection and
isentropic lift will bring moderate to heavy snow to areas along
and south of highway 460. With an easterly flow, the higher
accumulations will be across counties along and adjacent to the
Blue Ridge. Going into the afternoon, the surface low tracks off
the Southeast Coast, taking majority of the moisture and lift
with it. However, the area will sit in the deformation zone
between the surface low and upper level trough into Monday
morning. Even though snowfall rates will decrease Sunday night,
persistent light snow will continue to fall into Monday morning.
There is a possibility snow will continue through the day
Monday as the deformation zones hangs over the area, waiting on
a stronger upper level low over the northern Plains to kick
everything to the east on Tuesday.
Before we get to the first guess storm totals, there are
several questions yet to be answered with this event. At the top
of the list is the track of the surface low. A wobble north or
south will dramatically change amounts. Second, is the effect of
the dry air with the wedge. Does this dry air hold off
precipitation or does it contribute to higher totals early due
to fluffiness. Late in the event, snow is expected to be wetter
and heavier, compressing the drier fluffy snow already on the
ground. With all that said, our first guess totals through
Sunday night will range from 12-18 inches across the North
Carolina High Country and Grayson Highlands to 5-10 inches
across the Mountain Empire, New River and Roanoke Valleys to
Southside Virginia. North of highway 460, 2 to 6 inches are
possible. Again these are first guess estimates on a storm that
is 2-3 days away.
Temperatures will drop into the 20s Friday and may warm into
the upper 30s to lower 40s Saturday. Temperatures will again
drop into the 20s Saturday night, but may not get above freezing
Sunday. Clouds and possibly snow will hang around Monday with
temperatures warming above freezing but not making it out of the
30s.