427
FXUS62 KGSP 200735
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
335 AM EDT Sun Apr 20 2025

.SYNOPSIS...
A cold front will move into the region Monday night and stall,
providing a focus for mainly scattered afternoon/evening showers and
storms through much of the week. Temperatures will remain above
normal while humidity levels gradually increase.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM EDT Sunday: Mid-level anticyclone centered off the
Southeast Coast with a Bermuda high set up shop underneath will
continue to pull in stout WAA across the CFWA. This will lead
morning temperatures to run 10-15 degrees above normal. The early
Summertime type regime remains in place through the forecast period
with obvious cirrus coverage residing within the southwesterly
flow aloft. Closed upper low over the Southern High Plains will
shift towards the Midwest by the end of the period, which slowly
breaks down the anticyclone through the near-term, with gradual
height falls. In response, a trailing frontal boundary encroaches
the area from the west. Continued moisture advection will help keep
the top of the boundary saturated (top: ~850mb), leading to more
cloud cover during peak heating with roaming summertime cu. However,
with very warm profiles under the current regime, afternoon highs
are expected to top out ~10 degrees above normal. Compressional
warming overnight tonight and a slightly tighter pressure gradient
over the mountains may bring an uptick in winds by the end of the
period. Either way, widespread cirrus coverage will be evident and
continued WAA will lead to overnight lows remaining ~10 degrees
above normal across the CFWA.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 250 am EDT Sunday: A strong short wave trough/compact upper
low will lift north along the western periphery of the highly
amplified ridge progressing over the eastern states on Monday, with
resultant height falls overspreading our region late Monday into Mon
night. Associated frontal boundary and band of showers/embedded
storms is forecast to move into the southern Appalachians Mon night.
However, with deeper forcing lifting well W=>N of the CWA, and with
the boundary expected to become increasingly stretched parallel to
the upper flow in response to the next round of central Conus height
falls, UVV in the vicinity of the front will become increasingly
wanting across our forecast area...while moisture transport into the
CWA and instability profiles will also be...lacking. As such, the
band of showers and storms will struggle to survive the trip over
the high terrain, and Mon night PoPs will therefore range from
60-80% near the TN border...to only 20-30% across the foothills.

Having said that, the front is forecast to stall over or near the
forecast area Tuesday morning...and moisture pooling along the
boundary/afternoon destabilization should result in development of
diurnal convection, with numerous coverage possible across the
mountains and foothills...and scattered activity elsewhere.
Modest-at-most shear and instability parameters will constrain the
severe storm potential. There is some potential for cell training
along the boundary...but this is only expected to result in locally
beneficial rainfall. Temps will remain well above (i.e., by around
10 degrees) normal through Mon night, with some modest cooling
expected on Tue as a result of clouds, showers, and perhaps weak
cold advection across the northern zones.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 315 am EDT Sunday: A quasi-zonal flow will persist atop the
Conus through the first half of the extended, with perhaps some
amplification to the pattern occurring late in the week. A weak/
remnant surface boundary will continue to provide some degree of
focus for mostly scattered diurnal convection on Wed. The potential
for convection is expected to receive a bit of a boost on Thursday,
as a dampening short wave trough originating from the Southern
Plains brushes the southern Appalachians and vicinity and interacts
with a surface boundary that briefly sharpens in response to surface
high pressure moving across the Mid-Atlantic. Otherwise, little in
the way of an air mass change appears likely through the end of the
period, with moisture and destabilization expected to be adequate to
support diurnal, mainly scattered deep convective development Fri
and Sat. Modest mid-tropospheric flow will maintain unimpressive
shear parameters through the period, thus precluding any organized
severe storm threat. However, a few isolated pulse or multicell
severe storms will be possible through the latter half of the week.
Temperatures are forecast to be 5-10 degrees above normal through
much of the extended.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: VFR conditions will prevail through the
forecast period. BKN cirrus (200-250) will stick around through
much of the TAF period. South to south-southwesterly winds at
3-6 kts will continue through the morning hours and pick up a
few ticks by the afternoon (5-10 kts). Not expecting widespread
gusts, but can`t rule out a sporadic gust here and there during
peak heating. Guidance continues to develop SCT 040-050 cu during
the afternoon and evening hours before dissipating around sunset,
so kept this mention for the 06Z TAF update. Cirrus continues to
stream overhead overnight tonight, with southerly winds expected
at 3-6 kts.

Outlook: Dry and VFR continues Sunday night into Monday. Periodic
rain chances and restrictions return Monday night and may linger
through the middle of of next week as a frontal boundary stalls
across the region.

&&

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

&&

$$

SYNOPSIS...JDL
NEAR TERM...CAC
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...CAC