381
FXUS62 KGSP 171104
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
704 AM EDT Fri May 17 2024

.SYNOPSIS...
A warm front and weak low pressure system will bring frequent
chances for showers and thunderstorms today through the
weekend. Somewhat drier conditions return early next week resulting
in only isolated afternoon and evening showers and storms Monday
and Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 640 AM Fri: Abundant cirrus are creeping in as upper ridge
axis migrates east and net cyclonic flow develops aloft, with trough
slowly exiting the southern Plains and lower MS Valley. Vort maxes
left over from overnight Gulf Coast MCS look to advect northeast
to our vicinity later this morning, but latest CAM output suggests
this will have less energy to work with and there appears a low
chance of showers/storms developing as a result. Sprinkles will be
associated with the thickening cirrus. Meanwhile, warm front will
shift northward thru the Deep South, associated with developing sfc
low in MS/AL. The approach of this front warrants further increases
in PoP and expansion across the rest of the CWA in the afternoon,
perhaps along with diurnally driven showers/storms, with likely to
categorical chances for the whole area by late evening. This second
round of precip is more likely to induce thunder, particularly
in our southern half, with deep convection possible albeit most
likely elevated from the warm frontal inversion. This MUCAPE
appears meager enough that severe wx looks unlikely. Peak PoPs
will follow the warm front, behind which moist layer becomes
more shallow albeit with weak upglide continuing. Low stratus
are likely to develop in the evening and persist into Saturday;
unclear at this time whether the end of precip will be associated
with fog formation but a mild, muggy night appears a good bet. WPC
Marginal Risk seems to adequately cover the area most likely to
see convective rainfall rates thru tonight.

The clouds and showers will keep temps a few degrees below normal
in the west, but still may rise a degree or two above normal in
the east where these are less of a factor.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 245 AM EDT Friday: A positively tilted southern stream
upper trough will cross the TN valley on Saturday providing some
QG forcing atop the FA during peak heating. Precip from Friday
night may cause a frontal boundary to set up roughly along or just
north of the I-20 corridor early Saturday. The air mass south of
the boundary will be fairly unstable along with good bulk shear of
40-50 kt. For our forecast area, CAPE looks to be 1500 J/kg or less,
with the various deterministic models showing the maximum sbCAPE in
differing parts of the area. Shear will also not be quite as high
as to our south. So this muddies the severe threat quite a bit. The
latest CAMs show a rather disorganized convective mode across the
CWFA Saturday, and a marginal risk in the SPC Day 2 Outlook seems
reasonable. With more convection expected to our south, and veering
deep-layer flow to nearly due westerly, will also limit excessive
rain potential, as PWATs trend down. Despite plenty of cloud cover,
highs will be near normal with humid low-mid 60 dewpts.

The low pressure system slows down once it reaches the NC Coast
Sunday morning, with the CWFA in the NELY-flow side of the
system. Wrap-around moisture should keep skies cloudy to mostly
cloudy with showers and mainly general thunderstorms possible. The
air wrapping around the system should be less unstable and bulk
shear will generally 20 kt or less, so severe thunderstorm chances
will be low. Heavy rain may localize along the escarpment with
nearly parallel deep-layer flow and some ELY upslope, but overall,
no strong signals for excessive rainfall/flooding. Highs will be
kept below normal, especially across the NC foothills and Piedmont.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 315 AM EDT Friday: The low pressure system along the NC coast
should drift far enough east to allow more dry air to work into the
forecast area from the N/NE on Monday. This should allow for more
breaks in the clouds and lower precip chances. With more insolation,
could see diurnal convection across the mountains, with isolated
showers possible across the Piedmont, but severe storm threat
should remain low. Temps will be slightly below normal thanks to
continued cool NELY flow. High pressure builds in Tuesday, making
for largely dry wx across the area and temps returning to normal.

The 00z medium range guidance has come into better agreement on the
next cold front to affect the forecast area. Earlier guidance had
moisture and PoPs returning Wednesday, but now have backed off. So
Wednesday may end up being dry with temps warming to slightly above
normal. With an upper ridge building over the Southeast, the front
will weaken as it tries to push into the area Thursday. The 00z
guidance shows meager QPF response with the front, and isolated
to scattered convection is expected. The NBM PoPs may be a little
overdone, if this trend holds, but for now will keep the solid chc
PoPs in there. Slightly above-normal temps will continue thru the
end of the week.

&&

.AVIATION /11Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Relatively low confidence TAFs with
multiple sources of weak forcing and differing signals among
guidance members. Widespread cirrus associated with onset of
cyclonic flow aloft which will permit weak vort lobes to pass over
the region. Only very modest CAPE looks to develop the remainder
of the morning, and earlier expectations of early day SHRA/TSRA
have diminished. Cirrus deck however may bring a few sprinkles
by late morning. Some destabilization appears possible near peak
heating, when convective layer deep enough for TSRA at some of the
terminals. More widespread precip arrives with warm front tonight
and more isolated embedded TSRA are possible tonight. Warm front
appears likely to produce MVFR and then IFR cigs tonight, with
areas of fog developing after precip. Generally southerly winds
this period. Slow improvement out of IFR after 12z Saturday morning.

Outlook: Periods of convection, which could be widespread at
times, are expected through the weekend. Late night/early morning
restrictions in low stratus and/or fog will also be possible. Drier
weather is expected to return early in the next work week.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...Wimberley
NEAR TERM...Wimberley
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...Wimberley