975
FXUS62 KGSP 291851
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
251 PM EDT Sat Jun 29 2024

.SYNOPSIS...
Warming temperatures as shower and thunderstorm chances increase
ahead of a robust cold front arriving Sunday. Drier and cooler
conditions return Monday and Tuesday behind the front, before summer
heat returns on Wednesday and beyond.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 230 PM Saturday...An upper trough will dig across the Great
Lakes and Ohio Valley tonight, and allow a cold front to sag SW
toward the fcst area tonight. Very moist air mass in place with
PWATs near 2 inches will result in convection producing heavy
downpours. Fortunately, cells have some motion to them, and
training cells are not expected. Also, warm mid-level temps will
continue to limit strong updrafts for severe storms. So all in all,
welcome rainfall without any issues expected. Convective coverage
will be highest west and lowest east, and should diminish this
evening. Low-level flow will veer to SWLY, then WLY overnight,
with enough MUCAPE and upslope to keep at least a slgt chc of
showers near the TN border. Plenty of mid and high clouds around
should keep temps a few deg above normal, along with muggy dewpts.

The cold front will be just to our NW on Sunday, helping trigger
convection across eastern TN and in the NC mountains. There will
also be a pronounced lee trough setting up across the Piedmont,
providing convergence for convection. Guidance is in good agreement
the approaching upper trough and the aforementioned front and
trough should support decent coverage of showers and tstms across
the area. SBCAPE will range from 1500-2500 J/kg and 0-6 km bulk
shear around 20-25 kt will be enough for quasi-organized clusters of
storms drifting toward the east. A few storms may produce damaging
wind gusts, and the Day 2 SPC outlook of marginal severe for our
area looks good. Convection will likely get going late enough to
allow peak heating to get temps into the mid 90s, while dewpts
remain in the mid 70s across much of the Piedmont Sunday aftn. This
results in heat indices getting into the 100-107 range across the
I-85 corridor and southeast. Have issued a Heat Advisory for the
NE GA Piedmont, the Upstate, and SW NC Piedmont for Sunday aftn
into early evening.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 150 PM Saturday: By Sunday night, what is left of a frontal
boundary clears the CWA and dissipates to the south. Synoptically,
high pressure builds in from the west with an amplifying high over
the southern CONUS. To the north, a trough attempts to dive
southward and turns flow aloft form the NW. High pressure at the sfc
will also keep sfc winds out of the N/NW, maintaining a stream of
drier and somewhat cooler air for the short term. Modeled upper air
guidance shows a stout subsidence aloft with a mid-level inversion
at the top of the BL, snuffing out rain chances Monday afternoon and
into Tuesday. A break in the heat will occur Monday and into
Tuesday, before a snap back to summertime reality. As far as fire
concerns with drier air during this time, it will drop RH values
into the 40 percent range, but critical thresholds are not
anticipated. Winds could have some low-end gusts Monday afternoon.
Fuel moisture is dry, especially east of the mountains meaning
vegetation is more prone to ignition. Otherwise, temperatures look
to be a few degrees below climo until the next period.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 200 PM Saturday: The summertime pattern continues into the
extended. Tuesday night and into Wednesday, the trough off to the
north starts to deamplify as the ridge axis slides over the eastern
CONUS. A strong area of high pressure also grows over the southeast
and Mid-Atlantic regions. As the heights rise, so do the
temperatures. Guidance from the GFS and EURO depicts moisture
returning toward the end of the week as sfc flow remains light and
starts to veer more E/SE. The slow advection of moisture from
previous model runs, does keep dewpoints more reasonable and in the
low 70s by end of week. This will have a direct impact on heat
indices, especially those locations east of the mountains. 90s
should return by Thursday and beyond. Once the high pressure starts
to weaken on Thursday and Friday, a return to more diurnally driven
convection is possible across the mountains, though confidence is
low. All in all, the extended looks relatively dry, temps ramp up
through next weekend, and qpf response is minimal.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Scattered to numerous showers are forming
just west of a KAVL-KGSP-KGRD line, and with very moist air
mass, direct hits to terminals may result in IFR vsby in heavy
downpours. Convection will struggle to get tall enough for TS, so
only mention is at KAVL, where chances are highest. Despite the
good coverage, guidance agrees it will struggle somewhat as it
drifts toward KCLT, and with coverage expected to be much lower
there, no tempo for KCLT at this time. But will add mention to
KCLT in amendments, if trends change. Convection should diminish
this evening, leaving varying amounts of VFR-level stratocu. Flow
tonight is expected to be weak and more SWLY, with less MVFR or
lower cigs expected than we had this morning. Some fog and/or low
stratus may form at KAVL before daybreak. On Sunday, scattered to
numerous showers expected to form in the mountains toward end of
the 18z TAF period, with better chances of TS. Confidence already
high enough for a prob30 at KAVL and KCLT, with the other sites
likely needing PROB30s in the upcoming 00z TAFs. Wind will stay
SSE to SSW and light thru tonight, then begin to shift to WNW or
NW Sunday morning, except at KCLT.

Outlook: A cold front approaches the area on Sunday, resulting in
higher aftn/eve convective coverage. The front pushes thru and
stalls out just south of the area, resulting in quieter weather
for Monday thru midweek.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory from noon to 8 PM EDT Sunday for GAZ018-026-028-
     029.
NC...Heat Advisory from noon to 8 PM EDT Sunday for NCZ070>072-082.
SC...Heat Advisory from noon to 8 PM EDT Sunday for SCZ008>014-019-
     104>109.

&&

$$

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