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369
FXUS62 KGSP 112120
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
520 PM EDT Sat May 11 2024

.SYNOPSIS...
The weekend dry high pressure will give way to increasing moisture
on Monday with numerous showers and storms Tuesday and Wednesday as
low pressure moves by. After a brief stint of dry weather on
Thursday, showers return on Friday.

&&

.NEAR TERM /THROUGH SUNDAY/...
-- Changed Discussion --
As of 500 PM: A band of moisture can be seen on vis sat imagery,
across the Central Appalachians and eastern TN entering the NC
mountains associated with an approaching cold front. Scattered
shallow showers are mostly to the north, but should push into
the NC mountains within the next couple hours. The latest ACARS
soundings at KCLT show a pronounced inversion around 700 mb, but
soundings over TYS show the inversion a little higher, allowing
for slightly deeper convection. So as the front pushes into the
CWA, the combination of some frontal forcing and slightly deeper
convective layer may allow for some showers to survive across
the mountains and into the NC Piedmont. Most of the CAMs agree on
this, and so I`ve blended in some CAM guidance for the PoPs this
evening. Mostly sprinkles or trace rainfall amounts expected,
but a slight chc PoP mention seems warranted.

Otherwise...weak, transient upper ridge present over the SE Coast
between shortwaves. Although this feature is losing influence
over our CWA, a subsidence inversion remains around 700 mb. With
deep mixing and seasonable moisture beneath, abundant cumulus are
seen on satellite. These will persist through the afternoon. Very
subtle height falls will occur through early evening as the second
shortwave crosses the Virginias; associated cold front will reach
the TN/NC border around sunset and exit the lower Piedmont by
about midnight. The shallow instability will linger until the front
arrives, and convective layer looks to deepen slightly as inversion
weakens. This is most notable on the west side of the mountains,
and scattered showers are expected to develop near the border and
move over the NC mountain zones. Further south and east, the effect
will be weaker partly owing to downslope low level winds. Most
CAM runs depict the showers becoming increasingly isolated as the
front moves east of the mountains, such that a mentionable PoP
is still not forecast this evening for the mountains/Escarpment
near the NC/SC/GA border, or the I-85 corridor. A stray sprinkle
is possible and some low-impact enhanced gusts could be associated
with evaporating precip. Behind the front, skies will trend clearer;
continuing light winds look to keep min temps a tad warmer tonight
than last night, particularly in the Piedmont.

Surface and upper ridging will build over the area Sunday following
the departing wave. Winds will remain light and downslope into
afternoon; with that and with slightly higher thicknesses, max
temps should trend back to or even slightly above normal. Skies
will remain mostly clear perhaps aside from some cirrus.
-- End Changed Discussion --

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 1245 PM EDT Saturday: The wx will turn unsettled again to
start off the work week as a zone of moist upglide flow remains
progged to overspread the cwfa on Monday.  With moistening from the
top down, increasing clouds, and later day shower chances, maximum
temperatures should not reach climo, although the I-77 corridor, the
last to see clouds thicken, is slated for solid middle 70s for maxes.
The pattern is shaping up to develop in-situ damming Monday night as
weak upglide flow continues atop weak sfc ridging.  Expect dreary wx
conditions, rainy, drizzly and potentially foggy with low overcast.
Energy rounding the base of potent Ohio Valley upper low will eject
NE into the region on Tuesday.  Along with an associated slug of
deeper moisture, showers are expected to become widespread.  It
remains to be seen just how far north and west into the cwfa weak
sfc wedge bndry retreats to, and at this point, the sensible wx will
include at least elevated embedded thunder everywhere.  We will
continue to monitor model and ensemble trends of creeping positive
SBCAPE values into the Piedmont Tuesday afternoon and in concert
with deep shear profiles leading to a non-zero probabilty of severe
storms.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 130 PM EDT Saturday: The llvl flow is progged to veer to
westerly on Wednesday in the wake cool/occluded frontal passage.
Within the scoured llvls, Piedmont maximums will jump into the lower
80s and despite nominally lower sfc dwpts, the amosphere will become
moderately unstable within the upper level cool air coincident with
the passage of the upper trough axis.  At any rate, sensible weather
will be diurnally enhanced scattered to numermous tstms with a few
severe storms probable.

The consensus among the latest medium range model guidance is
trending drier for Thursday will an increasing probability that s/wv
ridge axis translating atop the region will suppress deep
convection.  The pattern is progressive though, and we are slated to
be under the effects of another period of deep moisture and lift
associated with another southern stream s/wv on Friday.

&&

.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: VFR. Cu generally with bases 060-080 will
be seen this afternoon, possibly dissipating for a time before
redeveloping in shallow unstable layer ahead of cold front, which
will reach the mountains around sunset and push past KCLT by 04z. A
few sprinkles along the front are likely especially near KAVL and
KHKY but impacts should be small enough that they are not included
in the TAFs. Low-end wind gusts are possible this afternoon, and
any SHRA this evening could bring down gusts of 20-22 KT. Excepting
KAVL, directions may prove variable early this aftn due to mixing,
but will prevail SW for the late aftn and evening; front will bring
them to NW`ly and also clear remaining cu. Dry with slightly weaker
winds Sunday, backing slightly with lee troughing.

Outlook: Moisture returns late Monday with active weather and
associated restrictions Tuesday and Wednesday.

&&

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

&&

$$

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