855
FXUS62 KGSP 190737
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
337 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 TONIGHT/...
As of 315 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 ahead
of it. The main impacts from these storms will be heavy rainfall,
via PWATs around 1.5" producing efficient rainfall rates, and
in some areas training with the boundary being parallel to the
mean flow. Recent activity has started moving a little faster as
outflows or the boundary orient more perpendicular. Regardless,
the area of concern for locally heavy rain is now the Lakelands.
Lighter stratiform precip will occur north of the front across the
Upstate urban corridor, seemingly via deformation on the north side
of the shortwave, but these rates are much less concerning. Updated
PoPs again thru the morning, mostly lower than what was sent with
the last update, and focusing further south now that convection
has fizzled well behind the front.

The main area of DPVA with the shortwave most likely will be
southeast of the CWA by daybreak, with the deformation zone starting
to shift south. Beneath the trough, 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 should continue to diminish
despite some lingering MUCAPE in the early part of the day in the
far south warranting the best chances there initially. 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. Storms likely will be slow moving but PWATs will be
considerably lower than what we saw overnight, somewhat mitigating
heavy rain threat. With the NE winds continuing, max temps will be
several degrees below normal despite partial sunshine. Remaining
PoPs will diminish nocturnally; some low stratus could develop
near the Blue Ridge Escarpment overnight in the wedgelike easterly
flow. Mins will be around normal.

&&

.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 /08Z 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