GSP
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 155 pm EST Saturday: A broad upper
trough will retrograde
slightly toward the center of the country and sharpen during the
short term, as a series of short wave troughs dig across the
northeast quadrant of the country. The upper
jet will strengthen
atop our region early in the period, with resultant tightening of
the temp
gradient w/in pre-existing
baroclinic zone allowing for
frontogenesis/
isentropic lift across the TN Valley and the southern
Appalachians late Sun night, and especially through the daylight
hours. Light precip should blossom across this region during that
time, with forecast soundings indicating a rain/snow proposition for
the
NC mountains.
For the Smokies and vicinity, soundings support mostly snow even in
the lowest valleys, with perhaps some rain mixing in at times.
Forcing and
moisture will be such that liq equivalent
QPF will be
marginal for
warning-criteria snowfall, but strong SW
flow could
provide enough enhancement from mech lift to push some locations in
southwest
NC over the top. Considering this, along with model trends
(which have been steadily trending wetter), and with the expectation
that the higher elevations will be exclusively snow lends enough
confidence to issue a Winter Storm
Watch for Graham and Swain
Counties from 12Z Mon through 12Z Tue. Considered a high elevation-
only
Watch, but prelim
accums are close enough in the valleys to
issue for all elevations. Locations to the north and east...mainly
across the TN border counties could see solid Advisory-level
snowfall. Otherwise,
PoPs Monday range from
likely along the TN/
NC
border, to slight chances across the foothills. If precip is able to
break containment into the I-40 corridor across the foothills, some
-SN will be possible there.
There is quite a bit of uncertainty as to how things will evolve Mon
night into Tue, as models are at odds in terms of their handling of
a short wave
trough digging toward the Southeast by the end of the
period...and its potential consequences for coastal surface
development. Guidance sources are split in spreading light precip
into the eastern half of our
CWA during this time frame.
Nevertheless, there is enough to go on to introduce small
PoPs
across the Piedmont Tuesday. If precip occurs, rain is the most
likely p-type, but there could be a brief transition to snow as
colder air begins spilling into the area at the end of the period.