670
FXUS62 KGSP 240723
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
323 AM EDT Mon Jun 24 2024

.SYNOPSIS...
A cold front will cross the area early this morning leading to
scattered showers and isolated thunderstorms, mainly across the
mountains. Drier and less humid conditions return behind the front
this afternoon into Tuesday. Humidity returns again on Wednesday and
lingers through the weekend. Another cold front will track across
the area Wednesday night into Thursday bringing better shower and
thunderstorm chances. Showers and thunderstorm chances may Friday
into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM: A weak "cold" front is pushing into the area. A band
of showers extends from near Hendersonville across the southern
Escarpment into north GA. This activity will run generally into
more stable air as it pushes further southeast, although in short
term progs some moisture pooling is evident near the front and
convection thus stands some chance of surviving for at least another
hour or two. Downslope flow however will be an additional limiting
factor, and thus it is not much of a surprise that CAMs depict the
current activity fizzling before it reaches the I-85 corridor. CAM
consensus does so far look to be timed well, although too focused
on the NW NC Piedmont. Made another tweak to PoP trends to depict
best coverage in the aforementioned areas, the western Upstate and
Savannah Valley. Precip should be pretty much over for the lower
elevations by 6-7 AM. Further upstream, some low cloud cover and
spotty showers are seen over the Cumberland Plateau/Mountains;
with upslope moisture remaining, saw fit to keep small PoPs until
8-9 AM along the TN border.

The aforementioned moisture pooling will keep dewpoints elevated
this morning, but diurnal mixing and developing NW winds will start
to eat away at the moisture after daybreak. 850mb drying should
set in by around midday as sfc high moves across the Ohio Valley,
which will allow dewpoints to drop more appreciably. NBM temps
proved just a little too cool yesterday, although the spotty cloud
cover may have had a bit of impact. Debris clouds associated with
the early morning precip should advect out during the early day,
and although some diurnal cu will develop we will have plenty of
sunshine this afternoon and continuing downslope. Temps should
be somewhat cooler in the mountains/valleys, but for the Piedmont
maxes end up about the same as yesterday. Dewpoints dipping into
the upper 50s and lower 60s will keep heat index well below Heat
Advisory criteria. As the high moves onto the Eastern Seaboard
tonight, dveloping easterly flow might generate a few low clouds
in our east, but likely of no consequence. The lower dewpoints
will allow min temps to cool almost to normal for the Piedmont,
and a couple degrees below normal in the mountains.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Key Messages:

1) Lower Humidity and Dry Weather Continues Tuesday

2) Humidity Increases East of the Mountains Wednesday Ahead of an
Approaching Cold Front

3) This Front will also Increase Shower and Thunderstorm Chances
Wednesday Afternoon into Wednesday night

As of 200 AM Monday...Dry sfc high pressure will remain over the
region Tuesday into early Wednesday before a cold front tracks
across the western Carolinas Wednesday night. Lower humidity will
stick around on Tuesday before increasing on Wednesday as winds turn
SW`ly ahead of the approaching front. Highs on Tuesday should climb
into the low 90s in the mountain valleys and low to mid 90s east of
the mountains. Highs on Wednesday will be a few degrees warmer,
climbing back into the lower 90s in the mountain valleys and the mid
to upper 90s east of the mountains Wednesday afternoon. Thus,
temperatures will remain well above climo through the short term.
Heat indices should reach into the lower 100s in the Charlotte metro
and the Upper Savannah River Valley Wednesday afternoon but should
remain below Heat Advisory Criteria (Heat Advisory criteria begins
at a heat index of 105 degrees). Dry conditions will linger through
at least Wednesday morning before shower and thunderstorm chances
increase from west to east ahead of the FROPA Wednesday afternoon
into Wednesday evening. Convection will linger through the overnight
hours on Wednesday as the cold front tracks overhead. Capped PoPs to
chance (45% or less) area-wide Wednesday afternoon into Wednesday
night as global models still diverge on the exact timing/coverage of
convection. Guidance generally shows 20 kts or less of deep shear
and less than 2,000 J/kg of SBCAPE ahead of and along the cold front
Wednesday, so the severe potential looks to be low at this time.
However, if storms are able to develop ahead of the FROPA during
peak heating on Wednesday, a few isolated strong to severe storms
cannot be entirely ruled out (with the main hazard being damaging
wind gusts). The severe wx threat will be highly dependent on the
exact timing of the FROPA so confidence on the severe threat remains
low for now.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Key Messages:

1) Humidity Lingers East of the Mountains through the Long Term

2) A Cold Front Will Sink South of the Area Thursday into Friday
but Shower and Thunderstorm Chances Linger Behind the Front

3) Another Cold Front Will Track Across the Area on Sunday Keeping
Shower and Thunderstorm Chances Around

As of 230 AM Monday...Hot and humid conditions, as well as above
normal temps, stick around east of the mountains through the long
term period. A cold front will gradually sink south across the
eastern third of the forecast area early Thursday before pushing
into the Coastal Carolinas early Friday. With dry sfc high pressure
expected to remain just north of the Carolinas during this
timeframe, shower and thunderstorm chances will linger across the
area through the end of the workweek. Capped PoPs to chance (30% or
less) area-wide for now. Heat indices should once again climb into
the lower 100s each afternoon across the Charlotte metro and the
Upper Savannah River Valley, but look remain below Heat Advisory
Criteria for now.

Another large upper anticyclone will build over the southern US on
Saturday before gradually retrograding westward throughout Sunday.
At the sfc, a cold front will track across the Midwest on Saturday
before pushing across the western Carolinas on Sunday. This will
keep shower and thunderstorm chances around through the weekend.
Went with low-end chance PoPs (35% or less) on Saturday with higher
chance PoPs (45% or less) on Sunday for now. Humidity looks to
increase slightly this weekend which may allow for heat indices to
flirt near Heat Advisory Criteria each afternoon in the Upper
Savannah River Valley (Heat Advisory criteria begins at a heat index
of 105 degrees).

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Weak sfc front to cross the terminal area
early this morning. This will bring an area of SHRA near KAVL
and potentially KGSP/KGMU/KAND before dawn. An isolated TSRA is
additionally possible, but confidence only high enough to mention
this at KAVL. Lower VFR clouds will develop as the front passes the
terminals, with a small chance of MVFR at KAVL as well. Winds will
shift to NW after the fropa, but not expected to occur at KCLT until
diurnal mixing begins around 13z. A very small chance of diurnal
convection exists well south of KCLT and the SC sites today, but
otherwise post-frontal drying and subsidence is expected to result
in just cumulus. Development of easterly flow tonight could lead
to some low VFR stratocu near KCLT/KHKY but of low impact. Brief
mountain valley fog not out of the question at KAVL after 06z Tue.

Outlook: Dry weather and suppressed convection again Tuesday. Widely
scattered SHRA/TSRA may return as soon as Wed aftn/evening, with
seasonable summertime weather returning then and continuing into
the weekend.

&&

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

&&

$$

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