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851
FXUS62 KGSP 041049
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
649 AM EDT Tue Jun 4 2024

.SYNOPSIS...
Scattered showers and thunderstorms are on tap today with afternoon
storms persisting into Thursday. Dry air will mix in Friday and
persist into the weekend with the next chance of thunderstorms
returning Sunday afternoon.

&&

.NEAR TERM /THROUGH TONIGHT/...
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As of 647 AM Tuesday: A batch of showers and a few thunderstorms
continues to lift across the Upstate at daybreak this morning along
with patchy fog and low stratus. This activity should push out of
the area over the next several hours with fog also quickly mixing
out after sunrise. The forecast was adjusted to boost PoPs generally
along and south of I-85 where ongoing storms are.

Otherwise, early morning water vapor satellite imagery depicts an
upstream shortwave trough sliding out of the Southern Plains and
into the Lower Mississippi Valley. Several convective complexes are
ongoing within this trough from Oklahoma to Mississippi where
forcing has been enhanced. Farther downstream, across the Carolinas,
weak shortwave ridging is shifting east and offshore with continued
onshore flow helping to support the transport of moisture rich air
into the region. Lingering buoyancy within this moist airmass has
allowed for several clusters of showers to fester through the early
morning hours, especially along the I-85 corridor. Patchy fog, some
of which could be locally dense, will also be a concern through the
early morning hours. This will especially be true across the most
favorable mountain valleys, such as the Little Tennessee. Any fog
will mix out quickly after sunrise with lifting and scattering of
any low stratus.

With time, the upstream shortwave trough will lift into the
Tennessee Valley by tonight. 850mb flow will also increase to 15-
25kts as a low-level jet over the Southern Plains also translates
east. This will in turn advect a deep moisture plume from Georgia
into the western Carolinas with PWATs surging to near 2". The 00z
suite of CAMs is in good agreement that scattered to numerous
showers and thunderstorms will be possible this afternoon within
this very moist and moderately buoyant airmass. Afternoon insolation
will support modest instability of 1500-2500 J/kg, although CAPE
profiles in forecast soundings will remain tall/skinny. Lapse rates
will also be poor with limited downdraft CAPE, which will ultimately
hamper severe weather potential. However, as with any summer
convection, a couple strong to isolated severe thunderstorms will be
possible with wet microbursts being the main hazard. The greatest
chance for an isolated severe storm will be with any clusters and/or
loosely organized line segments that can organize along composite
cold pools. Deep moisture profiles will also support efficient
rainfall rates, but ~20kts of flow within the cloud layer should
promote enough storm motion to limit a threat for flash flooding.
Locally heavy rates could still result in ponding/minor flooding of
flood prone areas, however. As has been the case the last several
nights, scattered showers and an isolated thunderstorm or two will
likely linger well past the diurnal maximum through the overnight
hours. Coverage may be greater tonight given continued moisture
flux/flow and the approach of the upper trough from the west.
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&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 200 AM Tuesday...The atmos remains active thru the short range
period. A full latitude trof will be working across the MS Valley
early Wed, which will maintain well defined upper difl flow over the
fcst area. Meanwhile, waves of vort energy will traverse the flow
and begin to break down an upper ridge during the afternoon. This
will combine with a destabilizing atmos to produce rounds of convec,
some of which could form multicell outflow cells in a weakly sheared
environment. With sbCAPE reaching arnd 1200 J/kg, strong updrafts
will be capable of producing large hail and severe criteria
outflows.

Things become more dynamic on Thu as a supported cold front
approaches and crosses east which looks to occur during max heating.
Shear levels increase and soundings show a tilted longer-lived storm
potential as the prefrontal environment becomes more unstable than
Wed due to warmer sfc levels. Thus, expect more of a severe threat
with isol supercells maintained along and ahead of a passing sfc
convg zone. With increasing dCAPE, the threat of damaging downbursts
will increase, however, low level helicity looks to decrease after
sunrise. So an isolated tornado threat will be non-zero, but not
great either. Highs Wed will reach right arnd normal levels. Warmer
BL air Thu due to increased llvl WAA will allow for highs pushing
near 90 F outside the mtns and the m80s across the mtn valleys.
Above normal lows are expected Wed night and near normal levels Thu
night behind the frontal zone.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 220 AM Tuesday...Upper heights begin to drop Fri as a
large and strong h5 low is blocked and deepens across the Glakes
region. The guidance is still in sigfnt disagreement with the
evolution of this low thru the latter ext range. The GFS is the most
dynamic and swings an active occluded frontal low into the FA Sun
afternoon into Mon, while the other op models are more progressive
with the upper flow and maintain a much drier pattern. Thus will
keep PoPs at low-end chance during that timeframe for now with
precip possibly maintained non-diurnally each night as well.
Otherwise and beforehand, deep nw/ly flow will produce a dry column
Fri and Sat with near normal temps, lower sfc dewpts, and less
humidity each afternoon.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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At KCLT and elsewhere: Several rounds of restrictions are expected
at all terminals through the TAF period. Ongoing this morning is a
batch of showers with a few embedded thunderstorms moving across the
Upstate. Showers may continue to impact KGMU, KGSP and KCLT over the
next several hours. In addition, fog and low stratus is also causing
issues at KAVL and possibly into KAND and KHKY. With time, showers
should lift east through the morning with fog mixing out quickly
after sunrise. Any lingering low stratus should also lift and
scatter. Heading into this afternoon, scattered to numerous showers
and thunderstorms are expected to redevelop with temporary impacts
possible at all terminals. Showers and a couple storms will likely
linger well into the evening and overnight again along with another
round of patchy fog and low stratus.

Outlook: Coverage of diurnal convection is expected to increase
Wednesday as a frontal boundary moves into the region. Morning low
clouds and fog will also be possible Wednesday morning and Thursday
mornings. Drier air will filter into the area Thursday afternoon and
Friday morning, reducing chances for convection and restrictions,
with relatively dry conditions continuing into the weekend.
-- End Changed Discussion --

&&

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

&&

$$

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