729
FXUS62 KGSP 190627
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
227 AM EDT Sun May 19 2024

.SYNOPSIS...
A low pressure system will exit off the Carolina Coast today, with
high pressure building in from the north. Relatively dry conditions
return for the first half of the week resulting in only isolated
afternoon and evening showers and storms in the mountains. A cold
front will bring better shower and thunderstorm chances back into
the forecast late in the week.

&&

.NEAR TERM /THROUGH TODAY/...
As of 200 AM: Gradual height rises over the Northeast CONUS
will continue this morning, and a weak sfc high will build down
the East Coast via that mechanism and as a shortwave continues
to drift east across GA and the Carolinas. A backdoor front has
moved through most of our CWA as a result. A few hundred joules of
MUCAPE remain invof the front and slow-moving showers and storms
have lined up along it, with new development now occurring from
Anderson to near Whitmire. The main impacts from these storms will
be heavy rainfall, with weak unidirectional flow parallel to the
front allowing training, and PWATs around 1.5" producing efficient
rainfall rates. Lighter stratiform precip will occur north of the
front across the Upstate urban corridor but these rates are much
less concerning. Short term progs depict the MUCAPE diminishing
only very slowly, and the front will sag south at a slow rate as
well, so some area of heavy rainfall looks likely to develop across
the Lakelands before dawn. As such fairly high PoPs are forecast
for most of our GA/SC zones thru then as well. Low level CAA will
however lead to a strengthening

The main area of DPVA most likely will be southeast of the CWA by
daybreak, but with it being overhead we retain pretty good lapse
rates through most of the daytime hours. The northeasterly flow
associated with the sfc high is deep and forcing really comes from
the CAA, with no appreciable warm upglide. So as the front sags
farther south precip chances generally will diminish north of it,
despite some lingering MUCAPE in the early part of the day. A
subsidence inversion will persist over most of the Piedmont and
should preclude new convection there this afternoon. However,
over the mountains, the inversion will be weaker but also some
degree of low-level convergence will be present owing to slightly
more backed flow behind the shortwave meeting the easterly flow
from the high. This should provide slight forcing. Deep dry air in
the mid to upper levels would appear difficult for the relatively
mild instability to overcome, so PoPs have been limited to chance
range in the mountains. Max temps will be several degrees below
normal despite partial sunshine.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 130 AM EDT Sunday: Subsidence from mid-level ridging
should keep most of the region capped Monday and Tuesday. The
exception will be the usual highest elevations of the NC
mountains, which may overcome the CIN and result in a few
showers and possibly an isolated garden-variety tstm during peak
aftn heating. An axis of dry sfc high pressure will set up
along the East coast, supporting mostly sunny skies both days.
Highs will be near normal on Monday (in the upper 70s to lower
80s in the mountain valleys and the Piedmont), and slightly
above normal Tuesday (mostly mid 80s). Patchy fog will be
possible, especially in the mountain valleys both Monday and
Tuesday nights, with lows near to slightly above normal.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 145 AM EDT Sunday: Upper ridging across the Southeast
and along the East Coast will begin to gradually break down,
as a series of shortwaves eject out of the Rockies. Wednesday
looks like the last dry day, with stronger capping resulting in no
mentionable PoPs and temps a few degrees above normal. From there,
a cold front is fcst to sag southeastward across the Ohio Valley
and bring a return of mainly diurnal convection to the area. Most
activity will be in the northern part of the forecast area Thursday
as the front approaches, but then expands south for Friday. A
pronounced shortwave trough crosses the area Friday, which may
enhance convective coverage and contribute to bulk shear. But
the 00z deterministic guidance is still not in great agreement
on placement of the front and resulting QPF response. The ECMWF
still is a little north of the area Friday compared to the GFS and
Canadian. Overall, a more active convective pattern is expected
to continue from Friday thru the weekend. Temps will continue to
be slightly above normal thru the end of the medium range.

&&

.AVIATION /07Z SUNDAY THROUGH THURSDAY/...
At KCLT and other sites except KAVL: Backdoor cold front has passed
KCLT/KGSP/KGMU, soon to pass KAND. The front should induce MVFR cigs
which are expected to diminish to IFR within the first couple hours
of the period. Front initiated SHRA/TSRA via lingering instability
across Upstate SC; peak threat of TS has likely passed for KGSP/KGMU
but a stray anvil strike is possible. KAND still may see a TS move
over. All these sites get -SHRA VCTS to start. Precip will focus
further south thru the early morning so TS drops off but precip
mention will continue through most of the morning owing to slow
motion of the front and possible redevelopment under approaching
shortwave. Cigs will lift by late morning and scatter in early
aftn. NE winds will continue thru the period with low-end gusts
really not out of the question any time thru sunset.

At KAVL: Sfc winds channeled northerly through today but easterly
low-level flow will provide a source of lift. Hence IFR eventually
expected to develop early this AM, and can`t completely rule out
a shower although not likely enough to mention. Weak low-level
convergence will persist over the Appalachians today along with
weak instability, so a PROB30 is retained for chance of isolated
or widely sct TSRA this aftn. Winds are expected to turn SE this
evening; shallow convection could continue and produce low VFR to
MVFR cigs before 06z, with more severe restrictions possible later.

Outlook: Late night/early morning restrictions in low stratus and/or
fog will remain possible toward daybreak Monday particularly in
river valleys. Stronger high pressure settles over the region Monday
and persists through midweek, but isolated mountaintop convection
still appears possible both Monday and Tuesday afternoons. Precip
and restrictions possible with next front arriving circa Friday.

&&

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

&&

$$

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