Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 190459
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1259 AM EDT Tue Mar 19 2024

.SYNOPSIS...
Drier and cooler conditions continue today as Canadian high pressure
moves over the Southeast. Warmer temperatures return Wednesday into
Thursday with continued dry weather. A low pressure system will
bring cooler temperatures and rain back on Friday, with rain chances
potentially lingering into early Saturday.

&&

.NEAR TERM /THROUGH TODAY/...
As of 100 AM EDT Tuesday: Made some minor tweaks to cloud cover
overnight based on the latest nighttime microphysics satellite
loops. Also made some tweaks to winds and gusts based on the latest
OBS. Widespread wind gusts are still being reported as CAA increases
within a tight pressure gradient across the NC mountains this
morning. Winds should starting decreasing over the next hour or so
as the pressure gradient starts to relax.

Otherwise...an upper trough will track over the Carolinas early this
morning leading to low moisture lifting across the TN/NC mountain
spine leading to continued to cloud cover. Low-level CAA will
continue filtering into the region this morning, allowing temps to
drop below freezing area-wide. The growing season has started across
the southern zones where a Freeze Warning remains in effect through
10 AM. Another dry day is on tap today, with RH values likely
dropping to 25 percent or less across the region. Winds and gusts
wont be as strong as yesterday, so a Fire Danger Statement may only
be needed for NE GA depending on how land managers feel about fuel
moisture levels. This concern will be coordinated later on during
the midnight shift. High temps will be held right around or a little
below normal Tue.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
As of 130 PM EDT Monday: Surface high sets up shop over the Gulf
Coast, while broad cyclonic flow aloft continues to church over
the eastern CONUS Tuesday night. Cooler temperatures aloft and
clear skies should allow temperatures to cool off, but radiational
cooling conditions will be limited as the boundary layer will
struggle to fully decouple before daybreak Wednesday as surface
winds remain elevated into the overnight period (5-10 mph). As
a result, overnight lows on Tuesday should be at or slightly
below normal for most locations. Dewpoint depressions will be
too wide to go along with light winds to forecast frost across
the area, especially in the zones that are officially in the
growing season. The airmass will modify very nicely on Wednesday
as heights recover while coinciding with southwesterly WAA and a
west-northwesterly downslope component (850 mb). Lots of sunshine
is expected and should lead to temperatures recovering ~10 degrees
compared to highs on Tuesday. Wednesday afternoon highs are expected
to run 5-10 degrees above normal. Low RH values will be in store
Wednesday afternoon with a well-mixed boundary layer, but winds
should remain light enough to help alleviate fire weather concerns
for most locations. Deterministic models continue to depict a
backdoor cold front dropping through the region late Wednesday
evening as a shortwave trough slips through the northeastern CONUS.
The front will be severely moisture starved, so precip will be hard
to come by as the parent low pushes from Ontario/Quebec into
Atlantic Canada by Thursday and the better forcing/moisture remains
well north of the CFWA. Increasing clouds and WAA will lead to
overnight lows Wednesday to be near-normal.

Conditions begin to take a turn on Thursday as an upper low
gets its act together over the Desert Southwest Tuesday night and
transitions across the Southern Plains and into the Lower MS Valley
by the end of the period. Diffluent flow starts to filter in as
a stout baroclinic zone really activates over the west/central
Gulf Coast. At the same time, a strong surface high will settle
across the Great Lakes region on Thursday. These components come
together at the beginning of the extended period, but in the
meantime, Thursday should remain dry with extensive cloud cover
and continued WAA. Afternoon highs are forecasted to be a few
degrees above normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 230 PM EDT Monday: The aforementioned upper low from the
short-term will open up into a shortwave as it encroaches the
region Thursday night into Friday. At the same time, the surface
high over the Great Lakes region will move into the northeastern
CONUS, setting up the stage for a CAD event as the area of high
pressure noses into the region. Good moist upglide and DPVA will
overrun the area as the onset of precip begins to spread from
the southwest to the northeast overnight Thursday. An expansive
precip shield will keep rain over the area through much of the
day Friday as a coastal low begins to deepen over the eastern
Gulf. 30-40 kt south-southeasterly LLJ will help to enhance rain
rates, while locking in the cold, stable dome across much of the
CFWA. Temperatures throughout the vertical profile indicates that
the p-type will remain all liquid outside of the highest peaks
in the northern mountains of North Carolina. Convective rainfall
rates shouldn`t be an issue either as this system lacks elevated
instability. Guidance are in good consensus with the overall
synoptic pattern, but differ in QPF amounts and timing from start
to end. Seems like a good bet that most of the precip will occur
Friday into Friday night, but some models keep precip going into
Saturday morning, which slightly lowers confidence. Either way,
not looking at a hydro threat with this event, just a cold and
dreary day as temperatures Friday afternoon will likely struggle
to get out of the 40s to low 50s over most locations.

The alluded coastal low is expected to move north, up the East
Coast Saturday into Sunday. In this case, near surface divergence
and a downslope component on the backside would allow for the CAD
to erode by the second half of the upcoming weekend. Surface high
quickly dives into the northeastern CONUS by Sunday as thicknesses
begin to recover. High pressure will remain in control through the
end of the forecast period, but the model guidance are showing a
digging upper tough over the western CONUS with an active southern
stream jet by the end of the forecast period. All signs point
to an unsettled weather pattern, but should hold off until after
D7 based on current trends. Temperatures will modify Sunday and
beyond as the CAD erodes and the sensible weather remains dry for
consecutive days as values during the rest of the extended will run
a few degrees above normal with the potential to be a little higher.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: VFR expected through the period for all
six terminals.  As high pressure filters into the area overnight
behind a reinforcing cold front, increasingly strong and gusty
NW winds will develop and bring gusts to all the TAF sites.
This should let up before daybreak, except at KAVL, where at least
intermittent gusts will persist into the first part of Tuesday.
Winds will take on a slight S component (though still predominantly
W) Tuesday afternoon as daytime mixing sets in.

Outlook: VFR conditions are expected thru the middle part of the
week. An active frontal system will arrive Thursday night into
Friday, with rainfall and associated restrictions possible.

&&

.FIRE WEATHER...
Fire weather concerns may return today with RH values falling into
the upper teens to mid 20s across the western Carolinas and
northeast Georgia. Winds will start out NW early Tuesday morning
before gradually turning SW (east of the mountains) and W/WNW
(across the mountains) by this afternoon. Breezy winds are expected
again today, with gusts ranging from 20 to 25 mph east of the
mountains and 20 to 35 mph across the mountains. These fire weather
concerns will be coordinated with land managers later this morning,
and another Fire Danger Statement may be needed, across NE GA.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Freeze Warning until 10 AM EDT this morning for GAZ018-026-028-
     029.
NC...Freeze Warning until 10 AM EDT this morning for NCZ068>072-082-
     508-510.
SC...Freeze Warning until 10 AM EDT this morning for SCZ008>014-019-
     104>109.

&&

$$

SYNOPSIS...AR/DEO
NEAR TERM...AR/MPR/SBK
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...MPR
FIRE WEATHER...AR


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