939
FXUS62 KGSP 121453
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
953 AM EST Wed Feb 12 2025

.SYNOPSIS...
Cold and rainy weather continues into tonight thanks to a strong,
slow-moving front before drier and warmer conditions return Thursday.
Dry but cooler weather is expected on Friday thanks to high pressure
building into the region. Another strong storm system will bring
widespread precipitation back to the region over the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 943 AM Wednesday: The forecast remains largely on track this
morning with a persistent band of showers training across the region
within a well established CAD regime. A brief lull in shower
coverage is ongoing, but this will not last long as an expansive
area of moderate, to at times heavy, rainfall is pushing northeast
out of northern Georgia. Made a slight boost to PoPs and shaved a
degree off of high temperatures to match latest trends. Temperatures
have slowly warmed along the escarpment and portions of Avery
County. A few observations at or just below freezing remain as of
this writing and the winter weather headlines will be maintained
through 1pm with additional ice accretion of 0.05-0.15" possible
through the rest of the morning.

Otherwise, cold pool remains entrenched across the CWA this morning
despite the supporting parent high weakening and moving well off the
upper Mid-Atlantic coast. Meanwhile, surface obs indicate the
prominence of the warm nose above the stable layer, as the high
elevations are the warmest areas of the CWA...with temps in the 40s.
Having said that, cold air has been stubborn to give up the ghost in
sheltered areas along the Blue Ridge escarpment, with a narrow axis
of 31-32 degree temps continuing generally east of the eastern
continental divide and roughly west of the 2500` elevation contour.
Freezing rain is therefore almost certainly continues in these
areas, with scattered power outages noted from Black Mountain,
across Spruce Pine, to southern Avery County. Considering current
temp/radar trends, it was necessary to extend the Winter Wx products
until 18Z/1300 EST. No changes are necessary to affected areas. to

Otherwise, CAD will receive a bit of reinforcement later today, as
1035+ mb surface high moves into southeast Canada. The combination
of this reinforcement along with continued diabetic effects from
falling precip will again keep max temps well below normal...only
slightly warmer than yesterday, if at all. Forcing is expected to
steadily weaken through the morning, but moist isentropic lift will
continue to produce widespread, at least light precip across much of
the area, with perhaps brief lulls possible. The next round of
organized/widespread precip is expected to spread into the area from
the southwest during mid/afternoon as speed max ejects from the
southern Great Plains. This will be followed in short order by
well-forced frontal band of showers. Very strong wind shear in
advance of the front will encourage CAD erosion, while pressure
falls W=>N of the area should instigate some northward movement of
the CAD boundary. However, the window for a warm sector to become
established across the area is very narrow, and based upon the
latest guidance, significant cold pool dissipation over our CWA
appears unlikely. Can`t completely rule out a minimal risk of a
brief severe storm, but the probability is only slightly greater
than 0. Heavy rain and the potential for localized flooding
therefore remains the greater concern. Additional rainfall is
generally expected to range from 1.5 to 2.5 inches. The greatest
risk for flooding will exist in in the vicinity of the Smokies,
where 1.5-2 inches has already fallen, although more localized flood
threats could develop depending upon how rainfall rates evolve
within the frontal band tonight. Having said that, considering the
dry antecedent conditions that preceded the event, and based upon
ensemble hydrograph guidance for forecast points in the Little
Tennessee drainage, we still don`t see the need now to hoist any
Flood Watches, but this could change based upon how ongoing rainfall
evolves throughout the morning.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
As of 146 AM EST Wednesday...

1) Drying and clearing expected early Thursday.

2) Warm and sunny weather continues Friday.  Chilly temps Friday
night.

3) Rain returns Friday night as cold air damming develops again.

Potent upper troughing will lift across the Ohio Valley on
Thursday and drive a strong cold front across the Carolinas the
first part of the day, bringing widespread rainfall to a rapid
halt by early Thursday afternoon.  Postfrontal NW flow will build
in across the region, and apart from NW flow snow showers along
the NC-TN border, the entire CWA should dry out and cool off.
Temps will be above normal on Thursday afternoon given sunny skies
and higher thicknesses than previous days...but will crash hard -
into the 20s - Thursday night as delayed CAA picks up.

Dry weather will continue on Friday as a compact surface high pivots
across the Mid-Atlantic beneath de-amplifying h500 ridging.  This
system will set up a brief period of NE flow across the Carolinas
as it pushes off the coast, resulting in a shallow cold air damming
configuration that will develop just in time for another round of
robust moist upglide beginning Friday night.  Expect the overnight
hours to feature a rapid increase in rain chances and murky fog/low
stratus, as the wedge becomes self-sustaining after precip onset
despite the loss of synoptic support from the departing high.
Temperatures will therefore be near or a little below normal on
Friday afternoon, and may barely fall to normal Friday night.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
As of 224 AM EST Wednesday...

Key Messages:

1) Widespread rainfall continues Saturday into early Sunday.

2) Drier and cooler conditions return Sunday evening and beyond.

Rainfall will continue on Saturday as a mature low pressure system
lifts up the Ohio Valley and the core of strong WAA continues
over the Carolinas.  Significant QPF is still forecast across the
Appalachians, peaking before dawn Sunday...with potential for more
hydrological impacts.  It now looks like strong mixing down from
within the warm conveyor belt will result in the gradual retreat of
the CAD wedge northward Saturday night, such that by early Sunday,
we`ll be in much more warm-sector-like air, with a deep mixed
layer developing by late Sunday morning and even the possibility
of some surface-based instability developing before the front
arrives by early afternoon.  Should this instability materialize,
given favorable shear profiles, an outside severe risk isn`t out
of the question.

Whatever the case, the cold front will cross the area early Sunday
afternoon, putting a swift end to both rainfall and any convective
threat that emerges.  Dry high pressure will build in for the rest
of Sunday and Monday, and temperatures will cool off significantly.
Some guidance depicts the arrival of a southern stream wave Monday
night, which could produce another round of rain toward the end
of D7.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Periods of mainly light/moderate and
accompany 2-5SM visby restrictions will continue across the Terminal
Forecast Area this morning, along with widespread IFR cigs. Tempo
LIFR cigs are also expected at most sites early in the period.
Another round of widespread/organized rain will move over the area
this afternoon, with more persistent visby restrictions expected.
LIFR cigs could become more prevalent, esp tonight. However,
guidance sources have been too pessimistic with LIFR cigs over the
past 24 hours...and this is probably tied to mixing from persistent
showers keeping clouds from crashing. With only brief lulls in
rainfall expected through the end of the period, this trend may
continue. Will therefore lean on IFR cigs, but bring in some sct
clouds at the LIFR level this afternoon into tonight. With the
exception of light SE winds at KAVL, light NE winds will continue
through tonight...with speeds more in the 5-10 kts range expected at
the upstate SC terminals this afternoon. As strong low level jet
translates atop stable surface layer w/ light winds tonight, LLWS
will develop at all sites between 06-12Z. Can`t completely rule out
a stray TS or two tonight/early Thu, but the probability is too low
for a TAF mention at this time. For KCLT after 12Z Thursday, showers
should finally come to an end by late morning, while restrictions
may start to improve beginning around noon.

Outlook: Precipitation will finally clear the area during the
morning hours on Thursday with gradual improvements to both
visibility and ceiling. A brief improvement on Friday before
widespread rain and flight restrictions develop again on Saturday.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Ice Storm Warning until 1 PM EST this afternoon for NCZ033-503.
     Winter Weather Advisory until 1 PM EST this afternoon for
     NCZ049-050-053-065-501-505-507-509.
SC...None.

&&

$$

SYNOPSIS...MPR
NEAR TERM...JDL/TW
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...JDL