021
FXUS62 KGSP 032323
AFDGSP

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

.SYNOPSIS...
Hot and humid conditions return for the second half of the week and
will linger into the weekend. Afternoon shower and thunderstorm
chances return on Thursday, mainly for the mountains. A cold front
will increase diurnal shower and thunderstorm chances across the
entire forecast area Friday into the weekend.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 600 PM EDT Wednesday: No major changes were needed as the
forecast remain on track. Dry conditions remain in place this
evening and will continue through the overnight hours. Some upper
level cirrus are streaming across northern NC from the north while
daytime cumulus continue across the mountains and along/east of I-85.
The cumulus field should dissipate around sunset with the loss of
daytime heating, but upper cirrus will gradually increase through
the evening hours. This increasing cloud cover, along with S/SW`ly
flow, will lead to lows around 5-7 degrees above climo tonight.

Otherwise, 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 through Thursday, while max
temps rise back to around 90 in the mountain valleys and lower to
mid 90s for the Piedmont. Winds through 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 and provide some
enhancement, 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; 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 /00Z THURSDAY THROUGH MONDAY/...
Key Messages...

1) VFR through the Period

2) Dry Conditions Linger East of the Mountains through the Period
but Isolated SHRA/TSRA Will Develop Across the Mountains Thursday
Afternoon/Early Evening

3) Wind Direction Will Mainly be S/SWly through the Period

At KCLT and elsewhere: Dry conditions will persist east of the
mountains through the end of the 00Z TAF period, but SHRA/TSRA may
develop at KAVL Thursday afternoon through early Thursday evening.
Thus, went with a PROB30 for TSRA at the terminal towards the end of
the TAF period. VFR conditions and S/SW`ly winds will persist
through Thursday evening across the terminals. Upper cirrus will
gradually thicken through this evening, with low-end MVFR cumulus
developing once again Thursday afternoon.

Outlook: Typical mid-summer humidity and diurnal convection will
continue into early next week, leading to scattered 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...AR
NEAR TERM...AR/Wimberley
SHORT TERM...SCW
LONG TERM...SCW
AVIATION...AR