GSP says I get a 33 deg rain
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 230 PM Thursday: An active pattern for the short term as
surface high pressure is nudged offshore and a series of shortwaves
swing through the region. Starting off friday night, a closed upper
low over the Central Plains lifts toward the northeast leaving
behind a shortwave trough approaching the Appalachians. An
approaching upper jet will assist with height falls ahead of the
shortwaves along with a strong low level jet advecting moisture into
the region Friday night. This will set the stage for precipitation
to ramp up over the Carolinas. One of the key features during this
time is the influence of the warm layer brought in from the LLJ and
creating a deep warm nose. As moisture aloft moves in, wetbulb temps
will cool the column of air and translate a saturated profile toward
the surface by late Friday night. Meanwhile, the remnant high
pressure to the east sets up an in-situ wedge of colder air ahead of
the precip. How much cold air remains in place at the onset of
precip is not entirely certain, but should be enough to allow for
near freezing temps well before daybreak.
The biggest concern for this storm system is the amount and location
for where snow, rain, and freezing rain will take place. At the
current time given the latest guidance, ice accretions of 0.05-0.24
are likely along the near the Blue Ridge Escarpment and NC
Foothills. Ice accumulations have increased in the
Henderson/Transylvania counties that could be locally higher than
0.25 inches. A Winter Storm Watch was issued for the Henderson
through Caldwell/Alexander counties and expanded to include all of
Transylvania, Polk and Rutherford. In SC, light ice up to 0.10 of an
inch could occur along and north of I-85 from Spartanburg to
Cherokee county, and into NC with 0.01-0.09 toward the south. Noting
the anticipated deep warm nose, snow is less of a concern, but the
NC mountains could see a trace up to 2 inches. Outside of the
mountains, a cold rain is most likely precip type. Now, the
challenges to this forecast come in the way of warm temperatures and
the amount of moisture that can return to the area. At this time,
temperatures from the NBM and CONSRaw show a swath of at or below
freezing temps along the Escarpment. Given the in-situ wedge in
place prior to precip arrival, temps are likely to reach these
values. Freezing rain chances would decrease if surface temps are a
degree or two warmer than current model guidance, increasing the
chance for rain to become the dominate p-type. However, current
guidance keeps temps at or just below freezing along the I-85
corridor and north. Confidence is increasing from moderate to high
that some amount of FZRA will occur in this region, before
transitioning over the rain after daybreak. With the current totals
being near or at warning criteria, the current watch would most
likely be upgraded to a Winter Storm Warning at a later forecast
issuance and a likely Winter Weather Advisory issued for additional
counties. Freezing rain should transition to rain around noon on
Saturday, with rain moving out of the area from west to east by
Saturday night. After this wave passes, a brief stint of NW flow
snow is possible if any shallow moisture can remain in place along
the TN/NC border, with a trace at best is expected.