-- Discussion containing changed information from previous version are highlighted. --
820
FXUS62 KGSP 240011
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
811 PM EDT Thu May 23 2024

.SYNOPSIS...
Temperatures will remain several degrees above normal each
day through Monday as humid subtropical air remains over the
Southeast. Chances for showers and thunderstorms will remain higher
than normal, with some chance lingering each night. A cold front
passing late Monday will bring cooler and drier conditions in the
middle of next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 5:45 PM EDT Thursday: Sct showers with embedded thunderstorms
continue to make their way east across western NC early this evening.
Thus far, nearly all of our GA and SC zones have remained precip free,
however a few cells are now developing over the NC/SC border and far
NE Georgia. We have yet to see any severe convection, but the environ-
ment remains conducive for some of these cells to become severe with
strong downbursts/straight-line winds being the main concern and dama-
ging hail a secondary concern.

Otherwise, the general trend today is for advancing shortwave energy
to steepen lapse rates and erode an already-weak cap over what are
otherwise excellent profiles for deep convection.  The best upper
forcing will not arrive in the western zones until c. 4pm, at which
point most of the CAM guidance depicts widespread convective initiation.
This`ll take place in an environment of only modest (<15kt) low-level
shear, but increasingly potent (>30kt) deep-layer shear. Consequently,
many of the CAMs depict some level of convective organization.
DCAPE values will also soar to 900-1200 J/kg in many sites outside
the mountains.  All that to say, developing cells will encounter
an environment ripe for severe weather.  What remains in question
is the exact evolution.  Some guidance sources - especially the
later runs of the HRRR and NAMnest - depict an initial wave of
weaker convection during the next 3-4 hours, followed by a second,
late evening round that won`t fully exit the area until midnight
or later.  The 12z cycle of the ARW, FV3, and NSSLWRF all depict
a more robust, semi-organized line crossing the area after 4pm,
and stripping the atmosphere of enough instability in the process
to effectively shut convection down thereafter.  Which of these
scenarios will actually play out is hard to say.

Once convection exits the area tonight, gradually clearing skies
should permit fog development.  There are early indications in
guidance that this won`t be restricted to the mountain valleys,
but may also occur in parts of the NC Piedmont.  Right now, it
seems like it`ll be patchy at best...but as always, we`ll need
to evaluate trends once convection is underway.  Fog will quickly
scatter out tomorrow morning, giving way to another partly cloudy
day.  Profiles should once again support some afternoon thunder,
with CAMs advertising ~1200-1500 J/kg sbCAPE and , but somewhat
more nebulous synoptic forcing and more borderline deep layer shear
owing to a less prominent upper wave than the one inciting today`s
convection.  Consequently, while some severe weather is certainly
possible tomorrow, it looks overall less likely than today.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 150 PM Thu: A short wave ridge builds over the area Saturday
then slides east on Sunday as a short wave trough crosses the area.
Any surface frontal features will be weak and likely remain north
and west of the area. A weak lee trough seems to be the dominant
surface feature if there is any. Convection should diminish Friday
evening with isolated showers possibly lingering overnight. Diurnal
convection returns Saturday, but the coverage while favoring the
mountains, remains somewhat questionable, especially over the
Upstate and NE GA given the ridge building in. That said, where
storms do form, isolated severe storms with damaging downbursts
would be possible given moderate instability, low shear, and mid
level dry air. Isolated heavy rainfall would also be possible.
Convection should taper off quickly Saturday evening.

Coverage on Sunday should be greater, still favoring the mountains.
The atmos could become very unstable with shear increasing to around
40 kts. This could lead to a more organized severe storm threat
adding large hail to the damaging wind potential. There is still
some uncertainty, so this will need to be monitored. Lows around 5
degrees above normal and highs 5 to 10 degrees above normal both
days.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 220 PM Thu: A phasing short wave digs a trough over the
eastern CONUS and crosses the area Monday night. The trough remains
in place as another phasing short wave moves through on Wednesday.
NW flow aloft will be over the area Thursday. A cold front will
slowly move toward the area Monday and across the area Monday night.
The front may stall near the area Tuesday before a weaker cold front
crosses the area Wednesday. Likely to good chance PoP expected
Monday with the front. Lower chance PoP expected Tuesday with
moisture along the stalled front, with only isolated mountain
showers with the Wednesday front. Some severe storms and heavy
rainfall will be possible with the Monday front. Much lower chance
of either Tuesday. Thursday looks to be dry. Temps start out above
normal on Monday falling to near normal by Thursday.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
At KCLT and elsewhere: Expect sct showers and thunderstorms to
linger across the area thru late tonight and into the overnight.
I have TEMPOs for tsra at all taf sites thru roughly 04z tonight,
with mostly just showers expected to linger after that. I kept a
mention of MVFR visby at KCLT and the Upstate terminals and IFR
visby at KAVL and KHKY owing to the elevated dewpts and rain from
earlier. It remains difficult to determine if things will clear out
enough overnight to permit any widespread low stratus development,
but IFR stratus is certainly not out of the question. For the time
being, I kept any lower clouds sct thru the morning hours. Winds
will continue to favor a SW direction for most of the period and
should go light and vrb to calm overnight at most sites. Expect
less coverage of showers and storms on Friday, but at least some
convection still appears likely. This is handled with PROB30s for
tsra beginning around 18z and running thru the end of the period
tomorrow evening. The evolution of any convection tomorrow remains
difficult to predict, thus confidence on timing and/or location
remains low.

Outlook: A unsettled pattern will linger thru the weekend and into
early next week, allowing for diurnal shower and thunderstorm chances
each day and fog development each night/morning.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...JPT/MPR
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...JPT