932
FXUS62 KGSP 031803
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
203 PM EDT Wed Jul 3 2024

.SYNOPSIS...
Hot and humid conditions will become established once again for the
second half of the week.  Afternoon showers and thunderstorms will
be possible each afternoon starting Thursday, especially over the
mountains.  A cold front may enhance thunder chances on Saturday.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 135 PM: Sfc high pressure now centered off the New England
coast maintains relatively dry air over most of our CWA, at
least compared to points south and west. Deep convection should
remain capped off by an inversion centered around 700 mb for the
Piedmont and northern mountains; the inversion is a bit weaker and
sfc dewpoints higher in the SW NC mountains and Savannah Valley,
evidenced by a well developed cu field. Still think a stray shower
could develop in the Balsams or vicinity this afternoon with the
addition of ridgetop convergence in such an airmass.

Upper ridge over the Appalachian region will become more positively
tilted as a shortwave moves south of James Bay; weak frontal zone
will lay out near the Ohio River by daybreak Thursday. Sfc high
will weaken further, while our low-level flow continues to veer to
southwest. This flow appears less likely to foster low early-morning
cloud cover than what we saw Wed morning, but should maintain an
upward trend in dewpoints thru Thursday, while max temps rise back
to the lower to mid 90s for the mountain valleys and Piedmont. Winds
thru the column will remain pretty weak. Subsidence inversion looks
weaker on prog soundings but still persists such that areas near
and southeast of I-85 still get below-climo PoPs for Thursday. The
inversion will weaken enough that updrafts over the mountains look
viable. CAMs however show only spotty QPF response in that area,
perhaps reflective of winds being too weak to enhance initiation
via upslope. A few vort blobs could eject from convection in KY/TN
nearer the front, though. We will advertise mainly 20-30% PoPs for
isolated or widely scattered coverage for most of our mountains,
and higher 30-50% values along the TN border. PWATs are mostly
below 1.5 inches and rainfall is not particularly likely to cause
flash flooding despite slow storm motion.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 120 PM EDT Wednesday: Mid level ridging will remain in place
across the region through the short range period. The expected
southwesterly low level flow will bring higher dewpoints back into
the area. The main issue is how high the will dewpoints get. Mid 70s
dewpoints are not that far away this afternoon, so they could easily
advect into our forecast area. However, with the dry ground in our
area we have to anticipate those readings could mix a bit lower
during peak heating. Confidence is not particularly high, but the
possibility of heat indices around 105 degrees exists in the lower
Piedmont and around Charlotte on Friday and Saturday afternoons.
Later forecast updates will have to fine tune whether this will be
an issue.

Otherwise, we do expect showers and thunderstorms to develop in the
hot and moist air in the mountains with the highest pops being on
Friday. Some storm activity will spill out into the Piedmont, but
pops will be lower there. Saturday looks like another active
convective day as a weak cold front drops into the area from the
northwest.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 130 PM EDT Wednesday: Mid level ridging will be in place
across the region with a seasonably warm and moist air mass
persisting. We don`t expect excessive heat indices but do expect an
active mainly diurnal shower and thunderstorm setup for Sunday
through early next week.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: Varying degrees of low-VFR cumulus will be
seen this afternoon, most common in the Savannah River Valley where
influence of dry Atlantic high pressure is weakest. KCLT will see
some clouds AOB 045 in the first couple of hours before bases mix
higher. Still expecting near-zero chances of diurnal convection
near the terminals today, but a stray shower could develop in the
mountains west of KAVL. Weak gradient implies variability will
continue in sfc winds this aftn and tonight, but direction is most
likely to be S to SW thru the period. As such moisture flux in the
PBL should not be as effective at producing stratus/stratocu Thu
morning as happened today, so no low clouds are mentioned in the
current TAFs. Isolated or widely scattered showers are possible
Thu aftn mainly over the mountains, but confidence too low to
mention at KAVL thru 18z.

Outlook: Typical mid-summer humidity and diurnal convection return
Friday and persist into early next week, leading to SCT TSRA and
possible restrictions each afternoon/early evening. Fog and/or
low stratus may develop each morning, especially for areas that
received rain the previous day.

&&

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

&&

$$

SYNOPSIS...MPR
NEAR TERM...Wimberley
SHORT TERM...SCW
LONG TERM...SCW
AVIATION...Wimberley