176
FXUS62 KGSP 241058
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
658 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 appears to have made it through
most of the area based on track of light showers and gradual veering
of winds to NW. The remaining shower activity in the Upstate could
drop a few hundredths of needed rainfall in a few spots, likely
fizzling or exiting the CWA before appreciable destabilization
can occur ahead of the front. Eliminated PoP mention in the NC
Piedmont and basically only reflect the motion of the current
showers. Still feature isolated PoPs along the TN border where
upslope cloud layer still looks healthy, but that too is expected
to slowly dissipate this morning. Dewpoints remain near 70 in
much of the Piedmont owing to moisture pooling near the boundary,
but diurnal mixing and developing NW winds will start to eat
away at the moisture by late morning. 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 /12Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Cold front will have passed the terminals
by 12z and no precip mention thus needed this morning. Winds will
shift to NW with onset of mixing, if not already there by 12z. A
small chance of diurnal convection exists well south of KCLT
and the SC sites today in post-frontal convergence, before more
substantial drying and subsidence can set in this afternoon. No
mention appears needed for this possibility either; low VFR cu
will be seen but could dissipate earlier than usual on account of
the drying. Development of NE flow tonight could lead to some low
VFR stratocu near KCLT/KHKY but of low impact. Some fog possible
in the Little TN Valley tonight but not currently expected at KAVL.

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