923
FXUS62 KGSP 261835
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
235 PM EDT Sat Apr 26 2025

.SYNOPSIS...
Dry and slightly cooler high pressure moves in for Sunday and
Monday. Daily chances of showers and storms remain small early in
the week, but increase steadily each day Tuesday through Friday.
Temperatures also will trend warmer each of those days.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 141 PM Saturday: Early afternoon water vapor satellite imagery
depicts a potent northern stream trough lifting across the Great
Lakes region. Surface observations also place an attendant cold
front across the spine of the Appalachians. The frontal boundary
will push across the area this afternoon through the evening hours
as surface high pressure slides across the Midwest and into the
Appalachians by tomorrow. Mostly sunny skies have allowed for modest
instability to build across the area within a broad northwest flow
regime. The arrival of mid-level dry air and forcing confined to the
frontal boundary will generally limit the coverage of additional
showers and thunderstorms along and ahead of the front. Nonetheless,
mesoscale guidance is in good agreement that isolated to widely
scattered showers and thunderstorms will develop along the front
this afternoon into the very early evening hours. A few showers have
already developed across the I-40 corridor with additional
development expected through the afternoon. Dry sub-cloud profiles
could support a couple locally strong wind gusts, but severe weather
is not expected. Any lingering showers will quickly exit the area
early this evening with dry weather quickly returning through the
overnight into tomorrow. Highs tomorrow will be 5-10 degrees cooler
compared to today.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 100 PM Sat, Key Messages:

1. Dry/subsident air will keep most of the area dry, stable and
mostly clear thru Tuesday.

2. Convection will be possible along the major ridges of the SW NC
mountains Monday afternoon, and across a broader area of the NC
mountains Tuesday afternoon. Severe and flash flooding threats appear
rather low.

3. Daytime temperatures return to about normal Monday and trend a few
degrees above normal Tuesday.

Sfc high will be centered over the Mid-Atlantic coastal plain from NY
to NC Monday, while an upper ridge axis remains west of the
Appalachians. Prog profiles reflect deep subsidence under the
influence of the sfc high. On its periphery, however, southerly flow
will bring subtropical moisture from the Gulf states to the upper MS
Valley, feeding into a strengthening cyclone. East TN and N GA will
experience the return flow and should destabilize diurnally on
Monday. Weak westerly steering flow could bring some of that activity
into SW NC, but ridges of the Smokies/Snowbirds/Balsams might
destabilize enough to see activity develop in situ. We will carry a
slight-chance PoP in that part of the CWA. Any activity likely would
diminish by early Monday evening.

The pattern progresses enough by Tuesday to reduce the influence of
the sfc high over the CWA. Actual sfc front associated with the low
near the Great Lakes will stall north and west of the CWA.  A weaker
subsidence inversion will make deep convection plausible over more or
less all of our NC mountain zones, with the best chance about 30%
near the TN border.  Little forcing will be present aside from the
instability, and we are able to retain unmentionably low PoPs for
most of the Piedmont.

Per GFS/EC ensembles, PWATs will not be all that remarkable even
Tuesday. Shear will be weak. DCAPE and sfc-midlevel theta-e lapses
are marginally supportive of a microburst threat, but with CAPE not
likely to exceed 1000 J/kg, storms are not expected to be vigorous
enough to support damaging winds. Locally heavy rain is possible.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 200 PM Sat, key messages:

1. Mainly diurnal convection Wednesday and Thursday with
chances/coverage trending slightly upward each day, compared to the
previous.

2. Shortwave moving into the area Thursday night or Friday may result
in overnight showers/storms, and also increase the potential for
organized storms and severe weather.

3. Max temps 7-10 above normal each day.

The upper ridge over the SE CONUS will be suppressed as shortwave
moves across the Rockies and then the southern Plains. This shortwave
looks to reactivate the stalled front and reinforce SW`ly return flow
into our area. That said, not a lot of meaningful change in the
pattern Wednesday, but slightly better lapse rates aloft along with
the return flow imply a minor uptick in diurnal shower/storm chances
that day.  Bona fide height falls occur over the CWA Thursday as the
shortwave axis reaches the Mississippi Delta region and thus chances
increase a little more. Timing of the shortwave passage varies
between models and ensemble members, but is currently expected Thu
night or Friday, with cooler/drier air reaching the area by Friday
evening behind the associated front. Carried 20-50% PoPs through
Thursday night given possibility of passage at that time, which
increase again diurnally Friday before diminishing. The duration of
these PoPs likely can be narrowed once models come into better
agreement on timing. Given the shortwave and proximity to the front,
0-6km shear will increase to 30+ kt at peak, particularly with any
convection that occurs Thursday night. MUCAPE still may be muted to
only 1000-1500 J/kg, and hodographs likely unidirectional, but some
multicell clusters producing a low-end wind threat and areas of heavy
rainfall could result if convection is able to keep going overnight,
and/or redevelops Friday.

Temps are not likely to trend cooler until Saturday, with highs
staying in the upper 80s across the Piedmont each afternoon and upper
70s to lower 80s in the mountain valleys.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: VFR conditions are expected to prevail at all
terminals through the TAF period. Morning low stratus has cleared
out with VFR conditions widespread this afternoon. A cold front will
push through the area this afternoon into the evening. Isolated to
widely scattered showers and storms are expected along the advancing
front with impacts most likely at KGSP and KCLT, but cannot be ruled
out at KHKY or KGMU. Otherwise, winds will shift to out of the
northwest and then northeast behind the front with only a few high
clouds lingering overnight.

Outlook: Dry conditions with VFR likely through early next week.

&&

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

&&

$$

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