767
FXUS62 KGSP 041733
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
133 PM EDT Tue Jun 4 2024

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

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1002 AM EDT Tuesday: No major changes to the forecast
this morning.  What`s left of a weak band of showers is rapidly
losing steam over the eastern SC Upstate, and will continue to do
so over the coming hour or so.  Patchy fog has largely scattered
out, although intermittent low-vis obs are still being reported
along the Savannah River Valley and some of the NC mountain valleys.

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.

&&

.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 TUESDAY/...
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 /18Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: A complex aviation forecast sets up for this
afternoon and tonight as multiple rounds of convection hit the area.
Already, scattered cells are popping up over the NC mountains
near KAVL and surrounding sites.  Most hi-res guidance agrees
that scattered to numerous shower and thunderstorm coverage will
expand across the entire terminal forecast area.  Some guidance
suggests a well-defined line will lift up out of Georgia late
this evening...such that at least for the Upstate terminals,
convection will last well past sundown.  Overnight, areas which
received ample rainfall can expect MVFR to IFR vis restrictions...as
well as widespread IFR ceilings.  More recent runs of the HRRR now
support some additional predawn showers, mainly across the Upstate
terminals and KAVL.  Diurnal convection is expected once again on
Wednesday, possibly a little delayed compared to today.

Outlook: Coverage of diurnal convection is expected to
increase Wednesday evening as a frontal boundary moves into the
region. Morning low clouds and fog will also be possible Thursday
morning. 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.

&&

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

&&

$$

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