349
FXUS62 KGSP 082254
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
654 PM EDT Wed May 8 2024

.SYNOPSIS...
Showers and thunderstorm activity will be more numerous ahead of a
strong cold front tonight into Thursday, with severe storms
possible. The cold front pushes east early Friday morning but
another system approaching out of the south may bring shower and
thunderstorm chances back during the day on Friday. Drier conditions
and below normal temperatures return for the weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 634 PM EDT Wednesday: The first wave of strong to severe
storms has moved east of the fcst area, so the Severe Tstm Watch
has been cancelled for the GSP fcst area. The remaining light
rain from the convective debris should clear the fcst area shortly
after 23Z. Thus begins our evening lull that most of the CAMs were
suggesting. We will turn our attention to the west to see how the
convection evolves over middle to eastern TN. Of note across the
western Carolinas is how the afternoon convection has laid out an
outflow boundary that runs from roughly Andrews/Murphy NC down to
Anderson and Greenwood. To the north/east of the boundary, the
atmosphere has become capped and has lost most of its sfc-based
instability. Unless there can be some recovery of the air mass
across that large part of the fcst area, it will be difficult
to get anything other than elevated storms. Note this will still
pose a threat for severe hail, but would limit the potential for
wind gusts and tornadoes, UNLESS we can get storms rooted in the
boundary layer once again. We will be minding the evolution of the
boundary layer over the next few hours. Meanwhile, along and S and
W of the aforementioned boundary, all hazards remain in play. It
is entirely possible that later tonight some kind of organized
deep convection will clip our southwest NC/northeast GA/western
SC zones, so stay tuned for that possibility and maybe another
watch for part of the region. So for this update, we make some big
changes to evening temps because of rain-cooled air, and also some
changes to sky condition and lower precip probs. The precip probs
ramp back up later this evening in anticipation of storms coming
in from the west over the mtns.

Some of the CAMs have convection marching across the mountains
and across the Piedmont overnight. Some guidance even indicating
multiple rounds of convection overnight. Hard to tell if the MCS
(or multiple MCSs) will be able to hold together and cross the
mountains. SPC has kept us in the Enhanced Risk (level 3 out of 5)
which is climatologically significant, but this is mainly for the
wind threat.

Otherwise...not quite as warm tomorrow but still mid 80s in the
Piedmont. Slight Risk in place on Thursday but that`s as the
convection slips south in the morning.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 100 PM EDT Wednesday: For the Thursday night period, the 12z
HREF and CAM consensus depicts just very limited and isolated deep
convection lingering from whatever daytime activity redevelops,
along with a smattering, but again limited response into the night
and mainly confined to the mountains.  Not unexpectedly, the pattern
atop the SE CONUS remains dynamic into Friday as energy rounding the
base of the upper trough will finally be again to shove lingering
sfc frontal zone downstream of the cwfa.  But before it does, we
will be wary for the threat for tstm encroachment and redevelopment,
along the front itself, and in addition, MCS/bowing cluster moving
in from Georgia.  Sensible weather will feature a shotgun mid-chance
pop for Friday with isolated svr storms possible mainly SE of I-85.
Will plan on overspreading the region with deep layered dry air
within the broad downward vertical motion behind the departing s/wv
axis Friday night.  Expecting to be under a well mixed and more
seasonable airmass within the deep cyclonic flow on Saturday
featuring maximum temperatures close to climo.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 315 am EDT Wednesday: A broad upper trough is expected to
progress across the East through the weekend, with dry air/pleasant
surface dewpoints supporting wide diurnal temp ranges...max temps
averaging around normal and min temps a category or so below climo.
By early in the work week, a split flow regime is expected to be in
place across the eastern Conus, with a short wave ridge developing
across the Southeast...downstream of a southern Great Plains upper
low. Global models are at odds regarding the evolution of this
feature, namely its interaction with the northern stream, and
eventual impacts on sensible weather across the Southeast. For now,
there`s enough of a signal to include chance PoPs across much of the
CWA by Mon night/Tue. Temperatures are forecast to be very close to
normal through the period.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Convection across the area will impact TAFs
through the period. Have handled this with a period of VCTS, TEMPO,
and PROB30. Afternoon convection may periodically wane but then
expect overnight MCS to develop. Confidence on exact timing of TSRA
not particularly high, but high on occurrence. VFR cigs will drop to
MVFR but cannot rule out brief IFR as well as patchy fog. Gusty
conditions expected with any thunderstorms that develop. Winds
generally SW through the period.

Outlook: A system lifting out of the south my increase shower and
thunderstorm chances again on Friday, but confidence on this remains
low. Drier conditions can be expected this weekend.

&&

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

&&

$$

SYNOPSIS...CSH
NEAR TERM...PM/TDP
SHORT TERM...CSH
LONG TERM...CSH
AVIATION...TDP