700
FXUS62 KGSP 091853
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
253 PM EDT Thu May 9 2024

.SYNOPSIS...
A cold front will continue to push east of the area, before another
system approaches Friday. Showers and thunderstorms are possible
Friday afternoon, before dry high pressure builds in from the north
through the weekend.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 230 PM: An area of light rainfall is moving quickly across
the southeast half of the CWA, associated with shortwave ripple
aloft. This will be the last gasp of precip for today as the
airmass remains worked over from the overnight storms and precip,
and subsidence in the wake of the shortwave looks to suppress any
new deep convection even after the cloud debris thins/exits later
this aftn. Temps have consistently run near the low end of the
guidance envelope for today and even where insolation is able to
occur temps look to will top out near normal.

Tonight, decreasing cloud cover should permit good radiational
cooling for a time. Some dry advection will begin overnight
as weak sfc low passes by to our north, pulling very weak sfc
front through the area. This will promote just enough drying to
maintain a dewpoint depression of a few degrees in the foothills and
upper Piedmont, and furthermore some gradient wind is expected to
persist. Thus, the likelihood of radiation fog/stratus looks small
in those areas and mins will remain several degrees above normal.

Mountain valleys are likely to see some fog, along with the
SE CWA border where that weak front doesn`t reach and instead
may serve to pool moisture. A couple hundred joules of CAPE may
persist there thru daybreak. An MCV or other remnant of convection
looks to round the base of the main trough in the morning and some
guidance depicts a round of showers passing thru the Piedmont at
that time. Partly cloudy skies will permit the return of warmer
temps, again being a few degrees above normal. 700-500mb lapse rates
will increase as main shortwave swings in, and isolated convective
development is not out of the question over the mountains. For
the aforementioned Piedmont areas, guidance members differ as
to how soon low-level airmass change begins; GFS for example
maintains poor low level lapse rates above the PBL and develops
only small diurnal instability. The NAM depicts favorable lapse
rates thru a deep layer and develops 1000 J/kg or more of CAPE in
the afternoon. All models depict strong deep layer shear, perhaps
60+ kt, so if timing of the shortwave trends slightly slower or
the low level lapse rates improve, we could see an isolated severe
threat develop mainly southeast of I-85 or east of I-77. The setup
warrants only a chance PoP in our south and east; FV3 and HRRR
show short updraft helicity streaks from a lone cell.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 1245 PM Thursday...An upper shortwave axis continues to swing
east of the area Fri night as a cP air mass mixes into the lower
levels. This airmass will slowly modify warmer over the weekend as a
small scale ridge gives way to another diving Canadian h5 trof Sat
afternoon. This trof looks to bring it/s own moisture and will
probably produce some rain showers across the NC mtns Sat afternoon
into the evening. No good chance of thunder during that time as sfc
td/s drop into the 40s and potential instability remains nil or
quite low. Drier conds with warming temps across the FA Sun as a
broad sfc high builds over the area from the west. Generally, both
days will be rather pleasant with highs a couple degrees below
normal Sat, then back to normal levels on Sun. Mins will likely fall
a couple degrees below normal each night.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 120 PM Thursday...A more springtime pattern returns during the
ext range. The latest guidance contines to show a subs zone becoming
displaced by waves of srn stream energy while a mlvl trof/low
travseres the MS to OH valleys. The surface response indicates an
opening GOM flow, which will supply a good amt of moisture to a
broad frontal system each day. Onset precip timing Mon is suspect
with the majority of models indicating a later timeframe than the
moister insitu wedge pattern progged by the latest GFS. In any case,
thunder probabilty remains low with non-conducive llvl thermal
profiles. By Tue, expect a better chance of afternoon thunderstorms
as a wavy cold approaches from the west and sfc dewps rise into the
u50s to l60s. The pattern remains uncertain, yet possibly active
into Wed as another round of srn stream energy may be pushing east
across the GOM coastline by then. High Temps remain near normal Mon,
then drop abt 5 degrees below normal Tue with the best chance of
widespread precip and cloud cover. Highs rebound to normal values
Wed. Lows begin the period near climo, then warm abv normal Tue/Wed
nights.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere: -SHRA over or near the Upstate sites and KCLT
through mid-aftn, associated with convective debris. TS not expected
thru tonight with airmass already having been stabilized/overturned
by the early morning convection, and subsidence increasing aloft
reinforcing cap. Some LIFR cigs are forming where rain has ended
in NE GA and chance of this reaching KAND is high enough for a FEW
LIFR mention this aftn. As high altitude cloud debris advects out
this evening and dewpoints fall behind dry cold front, radiational
cooling could allow fog/stratus to form with much of the area having
saturated soils. Most guidance depicts Td falling slightly more
quickly than T, and also light to moderate SW winds continuing,
so currently think fog is less likely than a cig, but even the
latter not being especially likely. Hence only SCT mention of IFR
clouds tonight at KCLT/KGSP/KGMU. A weak upper disturbance may
ride over the front late tonight and spawn weak convection between
about 10-16z but not confident enough on impacts to mention aside
from low VFR clouds at the SC sites and KCLT. An isolated strong or
even severe t-storm can`t be ruled out near KCLT in the afternoon,
but chance still too small to warrant mention at this range.

Outlook: Drier and likely VFR conditions can be expected this
weekend.

&&

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

&&

$$

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