305
FXUS62 KGSP 182319
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
719 PM EDT Sat May 18 2024

.SYNOPSIS...
A weak low pressure system will track east across North Carlina
through tonight, bringing another round of showers and thunderstorms
to the area this evening and tonight. The low will exit off the
Carolina Coast on Sunday, with high pressure building in from the
north. Somewhat drier conditions return early next week resulting in
only isolated afternoon and evening showers and storms. A cold front
will bring better shower and thunderstorm chances back into the
forecast late in the week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 705 PM Saturday: Ongoing convection developing in the vicinity
of the backdoor front is happening just as expected. This activity
has caused some hydro issues already due to slow moving storms. This
activity will gradually sink south into the rest of the CFWA through
this evening and into the early overnight hours. CAMs continue to be
consistent with developing deeper convection along the Escarpment
and then moving/consolidating along a back-door boundary slowly
drifting down from the N/NE. The depiction on the CAMs is more like
garden-variety storms and we are only in the Marginal Risk, because
the better effective shear is to our southeast. Suspect we will yet
see a few severe storms nonetheless. Also a concern will be the
heavy rain potential. The 12Z HREF showed 6hr probability matched
mean rainfall across parts of the foothills and northwest Piedmont
upwards of 2-2.5 inches, which is a decent response for this air
mass. The PW is high enough that we have a non-zero flash flood
concern, but the overall lack of organization points to more
scattered spots of heavy rain. However, that could change later this
evening if an area of stronger showers and storms over middle
TN/north AL closer to the center of the upper system survives past
the loss of heating this evening and brings a better swath of heavy
rainfall.

The mid/upper trof, positively tilted, is expected to move eastward
across the fcst area tonight. As this happens, we should see the
better mid/upper forcing slide to the east this evening. What we
lose at mid/upper levels we gain at low levels, so there should be
some organization moving in from the west this evening. However,
most of the CAMs weaken the convection to our west before it ever
gets here. We will just have to keep an eye on it, and particularly
the rainfall response. If the back door boundary makes it down
over Upstate SC, there could be enough low level convergence to
possibly anchor some storms near the Escarpment. Don`t think the
coverage of storms and duration will warrant any Flood Watch. Low
temps should remain about a category above normal.

On Sunday, the upper trof will gradually move off to the east. Drier
air moving down from the northeast will help to push the front
further down and south of the fcst area, so precip chances should
drop in the afternoon. The exception will be the mtns, as continued
low level easterly upslope will help to maintain showers and a
few storms. That flow regime should keep temps about five below
normal for the afternoon.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 130 PM EDT Saturday: Mid level ridging and weak surface high
pressure will be in place across the region during the short range
period. This will lead to a general drying of the atmosphere and
lack of rainfall both Monday and Tuesday. The exception to this will
be over the favored high elevations where a shower or two will be
possible each afternoon during peak heating.

With the ridging and more sunshine in place, afternoon highs will
climb from the upper 70s in the mountain valleys and lower 80s in
the Piedmont on Monday to the lower to middle 80s respectively on
Tuesday. In other words, near climo on Monday and slightly above
climo on Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 140 PM EDT Saturday: Mid level ridging will remain in place
across the region for the middle of next week, but a weak trof
should weaken the ridge by the end of the week. High temperatures in
the Piedmont are expected to warm into the middle to upper 80s
through this period with lower to middle 80s expected in the mountain
valleys, all a few degrees above climo.

A more active convective pattern is expected toward the end of the
week with the breakdown of the ridge.

&&

.AVIATION /23Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Lingering VFR/MVFR low clouds will continue
to fill in as ongoing thunderstorms moves from the I-40 corridor and
shifts southward through the evening hours. Included a TEMPO fo TSRA
and associated restrictions at all TAF sites With the NC TAF sites
starting now through roughly 02Z-04Z, while the Upstate sites get in
on the action a little later (01Z-06Z). Winds will shift behind the
thunderstorms as a backdoor front moves in and shifts winds to a
north-northeasterly component. Winds will gradually pick up in speed
behind the front as well, which helps prevent widespread fog
development. Lingering showers overnight into the mid-morning hours
will mainly hover over the Upstate sites and KAVL, but will be
isolated in nature. Another player in the forecast is the low
stratus deck that will develop behind the front overnight. Have all
sites going IFR starting overnight through mid-morning Sunday before
slowly lifting and scattering out by Sunday afternoon. Can`t rule
out LIFR cigs as well underneath the stratus deck at any of the
sites. Another round of showers and thunderstorms will be possible
across KAVL and maybe the Upstate sites, but confidence was only
high enough for a PROB30 mention at KAVL. Will have to watch trends
for the Upstate TAF sites by the 06Z update.

Outlook: SHRA/TSRA remain possible Sunday afternoon and perhaps
even Sunday night until stronger high pressure settles over the
region Monday. Late night/early morning restrictions in low stratus
and/or fog will remain possible Sunday night; isolated mountaintop
convection still appears possible Monday.

&&

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

&&

$$

SYNOPSIS...SCW
NEAR TERM...CAC/PM
SHORT TERM...SCW
LONG TERM...SCW
AVIATION...CAC