461
FXUS62 KGSP 200158
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
958 PM EDT Fri Jul 19 2024

.SYNOPSIS...
A nearly stationary front will meander across our region
through the first half of 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 SATURDAY/...
As of 1000 PM EDT Friday: A nice meso-low developed over Chester
County in SC and is lifting northward this evening. The "strongest"
shower and thunderstorm activity is within the vicinity of this meso-
low, so some gusty winds cannot be ruled out with this feature.
Weaker shower activity is noted lifting northeast across the rest
of the forecast area this evening. The main concern with leftover
convection will continue to be locally heavy rainfall. The severe
risk, which was minimal at best to begin with, is over thanks to the
loss of daytime heating. Main changes needed this update were tweaks
to PoPs (and thunder) through the period based on the latest high-
res guidance. Otherwise, no other major changes were needed.

Broad upper trofing to our north will flatten/deamplify tonight as
broad upper ridging persists to our west and to our east. A weak
upper shortwave will lift over our area from the SW tonight
providing some amount of additional support for scattered showers.
At the sfc, we will remain sandwiched between weakening high
pressure to our NW and the western extent of the dominate Bermuda
High to our SE. A weak low pressure center will move off the NC
Coast and along what`s left of a stalled frontal boundary. With
deeper moisture lingering over our region, we can expect showers to
linger into the overnight hours. Lows overnight should be near
normal for mid-July, with areas of fog/low stratus likely developing
around daybreak Saturday.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 130 PM Fri: Not really any meaningful change in the forcing
regime across the region thru Monday. Upper troughing generally will
persist over the lower Mississippi Valley; as shortwave fills and/or
advects toward the Mid-Atlantic coast late Sat into early Sun, weak
height rises over the Southeast are soon negated by upper low
swinging south out of the Missouri Valley. The seasonably diffuse
boundary or convergence zone remaining from the central Gulf Coast to
the VA/NC coast won`t become any better defined, but could pivot
and/or shift slightly further north by Monday. Its presence near the
region, combined with relatively deep SW flow and above-normal PWAT
values, suggest elevated precip chances each day: basically likely
for most of the Piedmont and categorical for the mountains. Any
northward movement in the boundary would probably result in a slight
uptick in daily dewpoints and PWAT, although only a minimal change in
those fields is depicted in synoptic guidance, so we cannot say with
much confidence that will actually increase precip coverage.

Mean cloud-layer flow and deep layer shear are nonzero but small, so
storms are likely to move only slowly, and could organize loosely
into clusters. Widespread cloud cover should limit diurnal temps,
keeping them 2-3 degrees below normal, and so diurnal CAPE should be
on the low side for the season as well. Sfc-midlevel delta-theta-e
values also will be muted on account of the moist profiles.
Altogether main impact weather for the short term looks to remain
locally heavy rainfall particularly where cells train.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 200 PM Fri: On a large scale, the overall setup remains in
place through late next week: deep Bermuda anticyclone to our east,
persistent trough centered in the mid-Mississippi Valley, and broad,
ill-defined frontal zone in between, likely remaining just to our
northwest.  The Bermuda high does look to strengthen Tue-Wed, and
that would seem only to push the front northward. However, by then
some guidance members depict the upper low or another embedded
disturbance moving toward the NE CONUS and driving the sfc boundary
eastward thru the Mid-Atlantic. This could allow the peak convergence
zone to shift back south into our area as soon as late Thursday, but
if so it would probably stall SE of the Appalachians to end the week.
Altogether, without a major pattern shift indicated by any of the
available guidance sources, we can`t confidently advertise a
significant trend in temps or precip chances. Daytime temps will
remain a little below normal due to cloud cover; PoPs diminish
slightly by Day 6-7 simply due to lower confidence with increasing
forecast range. Main concern will be slow-moving or training storms
producing locally heavy rainfall, and potential for deteriorating
antecedent conditions following what will by then be almost a week
under the influence of this moist and somewhat active pattern.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Complex 00Z TAF period on board thanks to a
stationary boundary over the western Carolinas. Rounds of widespread
SHRA will continue across the terminals through late this evening,
with some terminals seeing a resurgence overnight. Have a TEMPO at
KCLT for SHRA this evening, with prevailing SHRA elsewhere through
the evening hours. Plentiful low-level moisture will allow CIGS to
gradually lower this evening into the overnight hours, with IFR to
MVFR cigs developing around/after midnight, lingering through
daybreak. Cigs will gradually improve to MVFR levels by the mid-
morning to early afternoon. High-end MVFR to low-end VFR should
stick around through late Saturday afternoon before VFR returns
everywhere early Saturday evening. Patchy IFR to MVFR fog will also
be possible overnight into daybreak Saturday, especially across
terminals that received heavy rainfall. Vsbys should gradually
improve to VFR levels around/after sunrise. Winds will be calm to
light and VRB this evening into tonight across the terminals. Winds
will pick up out of the SW Saturday morning. Winds will gradually
increase in speed, ranging from 4-7 kts,  while remaining SW
throughout the day Saturday. Shower and thunderstorm coverage looks
to be lower Saturday afternoon/evening but went ahead and added
PROB30s across all terminals to account for TSRA. Confidence on the
timing of TSRA and SHRA through the period will be low as high-res
models are not in great agreement regarding the coverage/timing of
activity through the 00Z TAF period. The HRRR is more bullish with
the amount of convection on Saturday while the NAMNest shows less
activity overall.

Outlook: Expect scattered to numerous showers and thunderstorms each
afternoon/evening through early next week. Morning fog/low stratus
will be possible each day, especially in the mountain valleys and
across areas that received heavy rainfall the day prior.

&&

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

&&

$$

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