796
FXUS62 KGSP 241826
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
226 PM EDT Fri May 24 2024

.SYNOPSIS...
Temperatures will remain above normal through the holiday weekend
with a chance of afternoon and evening thunderstorms. A cold front
on Monday brings a better chance of showers and thunderstorms.
Cooler and drier conditions move in behind the front and remain
through the end of the work week.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 217 PM EDT Friday: It`s quiet across the forecast area as
convection initiates over east-central GA ahead of an upper wave
exiting the Mississippi Valley.  The latest mesoscale analysis
depicts 1500-2000 J/kg sbCAPE across the forecast area, corroborated
by a few recent observed ACARS soundings.  So, we`re more or less
waiting for the arrival of the synoptic forcing associated with
that upper wave to provide a trigger.  Temperatures are on track
to climb into the mid-80s this afternoon.

The 12z cycle of hi-res guidance has finally come into agreement
surrounding the evolution of this system as it arrives in the
Carolinas.  sbCAPE should continue to increase over the coming
hours, with the 12z HREF mean depicting peak instability of nearly
2000 J/kg...and higher-end values in excess of 2500 J/kg.  Shear,
meanwhile, is forecast to be moderate at best.  Once the wave
arrives, a weak 500mb speed max will skirt the southern zones,
but its core will remain displaced to the south such that even
more aggressive CAM guidance like the 12z cycles of the NSSL-WRF
and FV3 only depict some 25-30 kts of deep shear.  Enough for
some organization, most certainly, but not enough to expect a
groundbreaking severe event.  Rather, SPC`s Marginal Risk still
looks reasonable.  Given a distinct lack of low-level shear,
tornadoes once again appear unlikely, with the main threats being
large hail due to strong updrafts, and perhaps a secondary threat
of wind from areas of convection that manage to get organized.
At least upstream, cells aren`t moving especially fast, so despite
PWs of barely 1.5", there`s an outside chance of locally heavy
rainfall.

Convection should wrap up earlier tonight than it did last night
(although the latest run of the HRRR has come in with a band
of showers crossing the Upstate after midnight) and give way to
initially cloudy skies, which will gradually clear up as residual
cirrus drifts east.  Areas that get rain this evening can expect
some patchy fog before dawn, but that won`t last long before
skies clear.  Lows will fall into the mid-60s again.  Another
round of convection is expected tomorrow, but should be even less
active than today.  Weak ridging will begin to develop over the
Southeast CONUS overnight, and the only supporting upper feature
for convection will be an embedded shortwave that dips across the
Appalachians and into the Piedmont by afternoon.  CAMs suggest that
a line of showers and thunderstorms will cross the area during the
mid-afternoon, organized more by their supporting upper feature
than by any inherent storm-scale dynamics.  Sans much of an upper
wave to work with, there`s pretty good consensus that deep shear
will be <20kts, and so severe risk looks muted compared to today`s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 200 PM Friday: A short wave ridge builds in on Sunday but
there is a short wave trough that weakens as it moves through the
ridge. Guidance has backed off on precip chances in response, with
chc PoP north of the I-85 corridor and slight chc along and south.
Have followed this trend as well. Any storms that do fire could
become severe with moderate instability and shear, along with dry
mid level air, in place. Precip chances increase late Sunday night
into Monday as the ridge moves east and a stronger short wave digs
across the area. PoP still favors the area north of the I-85
corridor with likely PoP and chance along and south. Severe storms
look less likely even though shear remains moderate. There is less
mid level dry air and low level lapse rates aren`t as steep. Temps
will be up to 10 degrees above normal both days, with 90 possible
along and south of I-85.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 220 PM Friday: A series of short waves dig out a trough across
the eastern CONUS which remains in place through the end of the
period. Moisture lingers behind the the cold front moving through
Monday night, keeping a small chance of convection on Tuesday. Drier
and cooler high pressure builds in for the rest of the period. Temps
will remain above normal on Tuesday then fall to near normal for
Thursday and Friday.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Somewhat more clarity on the convective
forecast for today, with hi-res guidance now indicating that
convection will arrive in the Savannah River Valley and cross
into the Upstate around 5pm.  In light of this, TEMPOs for the
Upstate sites will begin 20-21z.  As the system pushes east,
guidance depicts it deteriorating.  This actually introduces a
little new uncertainty as to whether convection will actually
make it to KCLT...but have chosen to retain mention of TS, in a
shortened TEMPO group, for the evening.  Thereafter, some lingering
sprinkles may persist in the wake of the main wave.  Sites which
receive ample rainfall this evening are likely to see patchy MVFR
fog again overnight, as residual debris cloudiness thins out and
skies clear.  That will scatter out quickly in the morning, giving
way to another convectively-active day.  Timing is uncertain,
but guidance is in decent agreement on another wave of SHRA/TS
making its way across the area during the afternoon.

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

&&

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

&&

$$

SYNOPSIS...RWH
NEAR TERM...MPR
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...MPR