Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 172129
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
529 PM EDT Sun Mar 17 2024

.SYNOPSIS...
Drier and cooler conditions return Monday and Tuesday as Canadian
high pressure builds over our region. Warmer temperatures will move
in by mid-week with lingering dry conditions. A low pressure system
will bring rain chances back on Friday and lingering into Saturday.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 523 PM Sunday...no major changes to the forecast this evening.
Clouds are increasing again as moisture streams in from the Deep
South, but the likelihood of anything more than some sprinkles
across the southern tier of counties this evening remains minimal.

Otherwise...the large-scale pattern will change during the period
as upper zonal flow gives way to a stg h5 sw trof diving out of
the Glakes region tonight pushing into the area thru late Mon. This
will shunt a broad sfc trof east, while stg Canadian hipres dives
south and ridges in quickly from the northwest. There is a small
chance for minimal Glakes moisture to be lifted across the Apps
developing isol light precip tonight across the NC/TN spine,
however, confidence is too low for a PoP mention in the fcst.

The incoming cP airmass will create a stronger p/grad overnight and
winds will likely increase a little offsetting any good chance of
dense fog formation in the morning. Low-end gusts will increase as
well into the moderate range by the afternoon and with vertical dewp
mixing, sfc RH values will plummet to 25% or less across many areas
mainly across areas east of the NC mtns. With the aforementioned
wind gusts, fire weather issues will arise. Per the latest HREF,
the best locations for overlap of the more sigfnt winds and low
RH looks to occur across the NC foothills, NE GA and the nrn
Upstate. See the Fire Weather section below for more info.

Mins tonight will drop to arnd normal levels while highs Mon are
likely held a cat or more below normal, esp across the NC mtns
where the best llvl CAA will occur.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 145 PM EDT Sunday: Deep upper trough will be pushing into the
area as we move into Monday night, with cold Canadian high pressure
dropping into the Southern Plains. Surface pressure gradient will
still be tight so expect blustery conditions to continue overnight,
especially in the mountains. As we have been advertising for several
forecast cycles now, overnight lows are expected to be at or below
freezing by daybreak Tuesday morning, and Freeze Watch remains in
effect for areas where the growing season has started (GA/SC
Piedmont, southern NC Piedmont). Wind chills in the 26 across most
of the Piedmont and teens across the mountains will make for an
uncomfortable mid-March morning at the bus stop. Cool afternoon
highs with NW flow aloft and the surface high pressure shifting down
toward the Gulf, as well as lee-side troughing developing allowing
winds to back around to the SW. Very dry dewpoints and deep mixing
will drop RHs well into the 20s and some teens across the area so
definitely expect fire weather concerns, will just have to see how
strong the winds end up.

Surface high will modify somewhat with warmer temperatures Tuesday
night and a beautifully pleasant day on Wednesday. Dewpoints
increase only a little, still widespread 20%s for RHs, so fire
weather concerns persist with only minor improvement from Tuesday. A
shortwave pushes across the Great Lakes which will allow a dry front
to pass through the area, with minor sensible effects to be felt as
we move into the extended.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 215 PM EDT Sunday: As we move into Thursday, winds will shift
back around NW with a slight decrease in afternoon highs especially
across the northern tier as the aforementioned dry front pushes
through. Still lots of RHs in the 20s area-wide (some 30s in the
mountains) so not out of the woods yet on fire weather concerns.

Meanwhile, a cutoff low that had been hovering over the
Desert SW ejects into the Southern Plains and induces surface low
formation, pulling moisture up out of the Gulf. Significant
differences in the operational models at this time, with the GFS
showing a deep shortwave and the ECMWF having a broad wave. GFS also
suffering from significant convective feedback in the Gulf. What we
do see on operational models is confluent flow somewhere over the
northern reaches of the Mid-Atlantic into New England Thursday into
Friday, allowing a surface high to wedge down the Eastern Seaboard
in a classical CAD onset for Friday. However, the ECMWF has been
perplexingly dry (12z run coming in wetter). Both the GFS and ECMWF
do have an 850mb anticyclone off the SE coast which would be
expected for a damming scenario so it makes sense that the ECMWF
would begin trending toward the wetter sensible weather solution.
Checking out ensemble QPF, the mean is down only a smidge and the
75th percentile is as well from yesterday. That said, PoPs from the
blends don`t lend as much confidence given the weighting from the
drier earlier runs of the ECMWF. Precip moves out on Saturday as as
is typical post-CAD, should be post-scouring cold front.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: A broad sfc trof will continue to cross the
area this afternoon with little moisture as drying hipres works in
from the west. Expect little in the way of llvl clouds thru the
period with the majority remaining in the mid to upper levels. As
the high pushes in overnight, expect a tightening p/grad and sfc
winds will remain elevated enuf to offset a morning fog threat. VFR
conds continue thru the latter period with low-end nw/ly gusts
outside the mtns and likely more moderate gusts remaining at KAVL.

Outlook: VFR conditions are expected for the early to middle part
of the week.

&&

.FIRE WEATHER...
A dry atmos will continue to engulf the area Mon as a strong upper
trof approaches from the northwest. This trof will usher in a little
cooler temps and afternoon mixing heights will be slower to rise,
however, expect dry air within this layer to mix to the sfc during
the afternoon to create RH values arnd 25% or less mainly east of
the mtns, yet some mtn valleys may also see quite low RH levels.
This trof will also increase winds within the sfc-layer with gusts
reaching 25 mph or higher across NE GA, the wrn Upstate, as well as
the NC mtns. Due to the uncertainty with higher winds overlapping
spatially with the lower RH values, will coordinate with
State/Federal land managers on subsequent shifts for the type of
fire weather products to be issued.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Freeze Watch from late Monday night through Tuesday morning
     for GAZ018-026-028-029.
NC...Freeze Watch from late Monday night through Tuesday morning
     for NCZ068>072-082-508-510.
SC...Freeze Watch from late Monday night through Tuesday morning
     for SCZ008>014-019-104>109.

&&

$$

SYNOPSIS...TDP
NEAR TERM...MPR/SBK
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...SBK
FIRE WEATHER...SBK


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