147
FXUS62 KGSP 201849
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
249 PM EDT Sat Jul 20 2024

.SYNOPSIS...
A nearly stationary front will meander across our region through
next week providing a focus for above-normal chances of mainly
afternoon and evening showers and thunderstorms. Temperatures will
be near normal or just a bit cooler than normal.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 2:25 PM Saturday: Over the past few hrs cloud cover has
bkn up considerably over the area, with a healthy cumulus field
across much of the CWA. Widely sct showers are making their way
over the NC mtns and into the foothills, but we have yet to see
much in the way of any thunder/lightning. As instability increases
over this afternoon, we should start seeing some thunderstorms
develop.

Otherwise, broad upper trofing will linger well to our north
over SE Canada while upper ridging persists to our west and to
our east. An embedded upper shortwave will lift over the fcst
area from the SW today providing additional support for showers
and thunderstorms. At the sfc, what`s left of a stationary bndy
remains in place just to our south with weak low pressure centered
along the bndy lifting NE. Sfc-based instability is not particu-
larly impressive today, but deep-lyr shear does increase, mainly
across the Piedmont, as the upper shortwave moves through. This
increased shear could help produce a few severe storms, especially
over the Piedmont, with damaging straight-line winds being the
main threat. The isolated heavy rainfall and localized flooding
threat also continues. Convection tapers off this evening, but
isolated showers may linger well into the overnight. Low clouds
and areas fog will likely develop again overnight, with lows
temps near to slightly above climatology.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 100 PM Sat: Broad convergence zone on the periphery of the
Bermuda High more or less remains the primary feature of interest for
our CWA in the early week. Cloud cover will keep temps mild, so
instability will remain muted thru the period, though diurnal
convection posing a localized threat of heavy rain will remain the
main driver for PoPs and the most likely impact weather.

In this period, upper trough will remain centered in the mid-MS
Valley. A weak, possibly convectively generated vort lobe will ride
along the boundary in the exit region of the trough Sunday night, to
which some guidance responds with an uptick in convection overnight.
At least chance PoPs will linger throughout the CWA into Mon morning
for that reason. A more clearly defined shortwave embedded in the
trough will move toward the upper Ohio Valley during the day Monday.
Upper height gradient tightens surrounding that feature and this
leads to a slight increase in deep shear for Monday, and possibly
weak DPVA over our north and west during the afternoon.  PoPs trend a
little higher than Sunday, likely in the Piedmont and categorical for
the mountains.  However, as the wave passes by to our north it looks
to induce slight drying and a brief decline in PWATs, so a more
appreciable nocturnal lull will be depicted in PoPs Mon night.
Tuesday, another shortwave rotates in from the west, which will
reinforce the larger scale trough for the midweek period. The
approach of that wave will enhance moisture transport over the Deep
South and far SW Appalachians, so PWATs rise again Tue and
potentially offers another round of vort blobs advecting into our
west. In response, our PoP gradient becomes more west-east instead of
mountains-Piedmont, and trends a bit higher in the west and lower in
the east from Mon to Tue.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 200 PM Sat: It remains a challenge to come up with any clear
trend one way or the other in the weather for the second half of next
week. Major models/ensembles still show no stark differences in this
timeframe, with stalled frontal boundary persisting over the
Southeast. Thus, the period starts with a continuation of our mild
but stormy pattern. Bermuda High looks to peak in depth late Wed into
early Thu, before the established trough over the upper MS Valley and
Great Lakes begins to progress. Models do show subtle differences in
how this evolves, namely whether height rises in the lower MS Valley
(in the trough`s wake) allow the Bermuda ridge to effectively
retrograde, and/or whether the stalled boundary moves eastward by any
impactful amount. Based on ensemble depictions of PWATs, upper level
winds, and precip probs, the most likely scenario is that the
progress of the trough will briefly enhance rainfall potential in our
area circa Thursday--still likely diurnally influenced but with
increased coverage and rates, and a localized flood threat
continuing. The boundary then will pivot as the trough axis nears the
East Coast Friday night or Sat, and with somewhat more westerly flow
occurring aloft, midlevels will dry at least slightly and our PWATs
will trend downward. This would offer the possibility of more
sunshine for next weekend, and a return to more typical late July
temps and PoPs.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Expect another round of sct to numerous
showers and thunderstorms and associated restrictions this aftn/
evening across the fcst area. This was mostly handled with VCSH
and TEMPOs for TSRA going thru roughly 24z, or in the case of
KCLT, thru 02z this evening. SHRA may linger overnight with at
least MVFR cigs becoming IFR overnight with a decent chance for
MVFR visby at most terminals and IFR visby at KAVL and KHKY.
Much like earlier today, expect the lower cigs to linger thru
late morning at most sites with VFR returning for the last few
hrs of the period. Winds will remain SWLY thru this evening,
becoming light to calm later tonight. They will eventually pick
back up from the S to SW by the end of the period early tomorrow
aftn.

Outlook: Expect sct to numerous showers and thunderstorms each aftn/
evening thru the middle of next week. Morning fog/low stratus will
be possible each day, especially in the mtn valleys and across areas
that received heavy rainfall the previous day.

&&

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

&&

$$

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