394
FXUS62 KGSP 051420
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1020 AM EDT Wed Jun 5 2024

.SYNOPSIS...
Scattered showers and thunderstorms will develop this afternoon and
again on Thursday. Dry Canadian air will mix across the area Friday
and persist into the weekend. A chance of thunderstorms returns to
the region Sunday into Monday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1017 AM EDT Wednesday: Widespread low stratus remains in place
and has actually expanded eastward across the SC Upstate; however,
as daytime heating sets in it has started to lift...a harbinger of
its impending demise.  No major changes were needed to the forecast,
which was largely on track.  Blended the latest HRRRTL guidance into
the dewpoint and wind forecasts.  Some spotty showers have lifted
out of north Georgia into the area, much as the ARW and NSSLWRF
predicted, but they`re rapidly intruding into unfavorable, high-CIN
air over the Upstate, and their strenght is diminishing accordingly.

Otherwise, several shortwave perturbations are forecast to lift
across the southeast states and into the Southern Appalachians
today. The approach of the lead shortwave trough in concert with
another remnant MCV emanating out of an upstream MCS across
Mississippi/Alabama will provide more than enough forcing to
instigate numerous to widespread showers and thunderstorms through
the afternoon into the evening hours.

The 00z suite of CAM guidance has been consistent in depicting a
lead batch of showers lifting across the southwest mountains this
morning with coverage increasing across the mountains early this
afternoon. Activity will spread out of north Georgia, along with
lead development, with multicell clusters/loosely organized line
segments across the Upstate and into the North Carolina foothills
and Piedmont. Late erosion of the morning clouds may hamper the
magnitude of insolation and resulting destabilization, but modest
surface-based CAPE of 1500-2000 J/kg should be relatively easy to
come by within a very moist airmass. Lapse rates will remain poor
and nearly moist adiabatic with weak downdraft CAPE and tall/skinny
CAPE profiles. While this will not be the most favorable environment
for microbursts, increasing 850mb flow late this afternoon into the
evening associated with a weak low-level jet translating across the
region, may prove sufficient for loose convective organization. As
such, a few instances of locally damaging winds will be possible
with any clusters/line segments that can organize along a composite
cold pool and/or outflow boundary collision. Of note, though, is
that the increasing low-level flow with the low-level jet, while
weak, results in non-zero hodograph curvature. 0-1km shear and SRH
approaches 20kts and 100 m2/s2, respectively, in several near-storm
forecast soundings along the I-85 corridor. While probabilities
are rather low, a brief tornado cannot be completely discounted,
especially should there be a favorable outflow boundary interaction
that can locally enhance SRH and ingestion of horizontal streamwise
vorticity.

At least scattered showers and a few thunderstorms will likely
linger into the evening hours with a handful of showers festering
overnight. There are indications that a line of thunderstorms over
Tennessee just ahead of a cold frontal boundary will make a run at
the mountains around or shortly before daybreak. Guidance differs
with how these storms may evolve, thus have kept rain chances in
the likely rain and not quite categorical just yet. Otherwise,
another mild night can be expected with upper 60s to low 70s
dewpoints greatly limiting any cooling.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 105 AM Wednesday...The synoptic pattern has become more
progressive over the past couple model runs. There is now decent
agreement with a h5 s/w crossing the area before 18z Thu. Model
soundings during the afternoon look less impressive as the mlvls
warm and instability likely remains below 500 J/kg. There still
looks to be a chance of morning convec ahead of a sfc bndry, but
most of the storm activity will remain general in nature. A more
convectively suppressive environ builds in Fri as deep layered flow
becomes nw/ly and the column dries out. This drier air will persist
into the ext range and by Fri afternoon RH values will drop into the
30 percent range. Highs will likely increase a couple degrees abv
normal each day with increasing insol, while lows begin arnd normal
Thu night then fall below normal Fri night.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 130 AM Wednesday...Made little changes to ext range fcst. The
guidance continues to depict a dry atmos in place over the weekend,
before a dynamic system pushes in Sun night into Mon. Broad surface
hipres will keep precip activity shunted west Sat, before a stg
upper low swings a cold front into the area Sun. This front looks to
lose upper support as it interacts with an existing flat ridge.
Profiles remain mostly stable each afternoon as a sfc bndry possibly
pushes thru the FA Sun night. The latest ECMWF is still an outlier
with stalling the front over or just south of the fcst area, which
would increase precip and thunder chances late in the period. For
now, will continue to advertise low chance PoPs Sun into Tue due to
uncertainty with the evolution of large scale pattern. Temps look to
remain arnd normal levels each day with low humidity values Sat
becoming more humid into the early next week.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Another pessimistic aviation forecast again
tonight with multiple rounds of restrictions expected at all
terminals through the TAF period. A widespread deck of low stratus
clouds is ongoing with a couple instances of patchy fog. Ceilings
range from MVFR to LIFR within this stratus deck with restrictions
expected to continue for a couple more hours with an eventual return
to VFR by late this morning. Thereafter, another round of numerous
to widespread showers and thunderstorms is expected through the
afternoon hours into the early evening. As such, temporary
visibility and ceiling restrictions can be expected. Showers will
likely linger into the evening with a brief return to VFR before
another low stratus deck builds in overnight.

Outlook: Yet another round of convection may be possible Thursday
with associated restrictions. Drier air moves into the area Thursday
night into Friday morning with improving restrictions into the
weekend.

&&

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

&&

$$

SYNOPSIS...SBK
NEAR TERM...MPR/TW
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...TW