072
FXUS62 KGSP 122112
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
512 PM EDT Fri Jul 12 2024

.SYNOPSIS...
Scattered showers and a couple storms will continue through the
early evening hours today, mainly along the I-77 corridor. Dry
weather returns for the weekend and into the beginning of next week
as high pressure builds across the area. This will support a return
of hot weather with afternoon highs climbing into the upper 90s to
low 100s. A pattern change is expected mid week into next weekend as
a cold front stalls across the area bringing above normal rain
chances and cooler weather.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 500 PM EDT Friday: A few showers and thunderstorms continue
east of the I-77 corridor this afternoon, leading to extensive cloud
cover and cooler temperatures. The latest SPC mesoanalysis shows a
bullseye of 2-2.5" PWAT values east of I-77, with PWATS generally
below 2 inches along and west of I-77. With the area still under the
influence of peak heating, SBCAPE values are ranging from 1000-2000
J/kg as of the writing of this AFD, could still sees some isolated
showers and thunderstorms develop west of I-77. Two Flood Advisories
(Union County in NC and Cabarrus County) and one Flash Flood Warning
(Mecklenburg County) remain in effect through the next few hours.
With convection starting to push east of the CWA, the heavy rainfall
threat should come to an end soon.

Otherwise, a surface boundary stretched across the Coastal Plain of
the Carolinas will have a weak surface low ride along the boundary
will slowly lifting north through the period. Most of the area will
be on the subsident side of the low and thus, limiting shower and
thunderstorm potential west of the boundary. As a result, only token
PoPs are placed in the Upstate, with the Upper Savannah River Valley
likely to miss out on any of the action that decides to initiate as
the mountains will be inclined to develop some orographically
enhanced convection. Temperatures will vary with afternoon highs
slightly above normal west of I-26 and slightly below normal along
and east of the I-77 corridor due to the amount of cloud cover and
precip.

The surface wave will lift northeast of the CWA overnight as the
mid/upper-level low gets absorbed by the upper troughiness over the
northeastern CONUS. However, the subtropical moisture in association
with this system will be slow to lift northeast and should keep a
few lingering showers in the eastern portions of the CWA into the
early evening, so kept token PoPs for the CLT metro through ~03Z
Saturday. Summertime regime will be in store for Saturday as weak
high pressure sets up over the CWA, while the Bermuda High
reestablishes its position over the western Atlantic and slowly
turns surface winds back out of the south-southwest by the end of
the forecast period. With 594-596dm thicknesses in place, and
dewpoints ranging from the upper 60s to lower 70s, expect a few
locations south and east of I-85 to see heat indices climb into the
low 100s. QPF response is relatively dry throughout much of the day
outside of orographically enhanced convection as warm air aloft will
help to cap the atmosphere. Afternoon highs on Saturday are expected
to rise a few degrees above normal.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 224 PM Friday: Broad upper troughing will be draped from the
Northern Plains across the Great Lakes and into New England. Farther
west, a stout 600dam upper ridge will be parked over the Four
Corners region with broad ridging extending across the Southern
Plains and into the Lower Mississippi Valley. Ridging is forecast to
build east through the later half of the weekend and into the start
of the new week with heights rising across the Southern Appalachians
along with an uptick in low-level temperatures. This will support
rather hot temperatures with afternoon highs climbing into the low
to upper 90s on Sunday and mid 90s to low 100s on Monday. Any good
news, though, is that the frontal boundary that has been waffling
across the I-77 corridor is forecast to shift back east as flow
shifts to out of the west/northwest. This will shunt higher
dewpoints and richer moisture into the Coastal Plain with dewpoints
able to mix out more efficiently each afternoon. This will in turn
help keep heat indices in check with low 100s along and south of I-
85 on Sunday. While dewpoints will remain relatively low on Monday,
temperatures in the upper 90s to low 100s will be hot enough that
even lower end dewpoints could end up supporting heat indices near
advisory criteria (105 degrees) and a heat advisory may ultimately
be needed. Subsidence from the upper ridge and a lack of deeper
moisture will preclude diurnal convection across much of the area,
but an isolated shower and/or thunderstorm cannot be completely
ruled out across the mountains.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 232 PM Friday: The blowtorch will continue as we head into mid
week, especially on Tuesday, as the 850mb temperatures peak near 24
C. This will support at least one more day of hot weather with
afternoon highs once again peaking in the mid 90s to low 100s. A
potent upper trough is also progged to swing across the Northern
Plains and into the Great Lakes on Tuesday with an attendant surface
cold front dropping across the Midwest. Surface high pressure will
have also shifted offshore with low-level flow backing to out of the
south. This will allow for gradual moisture return into the area off
the Gulf of Mexico and eventually the Atlantic Ocean. PoPs slowly
return on Tuesday, but most of this activity may remain just south
of the area within the initial moisture return across the Deep South
into Georgia. A noticeable pattern change is still on tap for
Wednesday into next weekend as the upstream frontal boundary
approaches and then eventually stalls across the area as the upper
trough lifts across the Ohio Valley into New England. Lingering low-
level warmth may result in one last day of heat concerns on
Wednesday, but this will be conditional with PoPs quickly ramping
back up within the leading edge of moisture return. A more robust
afternoon cumulus field and an early start to diurnal pulse
convection may limit heating and preclude the need for heat
products, but this will have to be assessed closer to the day. By
Thursday into next weekend, guidance continues to depict the frontal
boundary stalling either across or near the forecast area as the
front becomes oriented parallel to upper westerlies with the parent
trough lifting out of New England. This will result in above average
PoPs each day in the likely to categorical range, which will
hopefully bring much needed rainfall and cooler temperatures to the
area.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: VFR conditions are expected at most sites
through at least this evening. KCLT has bounced around between VFR
and MVFR as a disturbance closer to the coast brings in extensive
cloud cover and increased SHRA/TSRA chances. Kept a TEMPO for TSRA
mention at KCLT through 00Z as a result. This has expanded into
KHKY, but not expecting associated restrictions outside of a passing
SHRA/TSRA. However, model guidance hints at an IFR/LIFR of low
stratus in association with the disturbance and should spread into
KCLT and KHKY from the east, which has been reflected in the 18Z TAF
update. The RAP shows this cloud deck expanding into KGSP/KGMU, but
confidence is low for this development as its the only model
indicating this potential, so only kept a FEW015 mention to hint at
the possibility. MVFR vsby restrictions will be in store as well,
especially in locations that receive rainfall through tonight. Model
guidance is being stubborn as far as lifting the deck of low stratus
out by daybreak and keep restrictions in place through mid-morning
instead. Otherwise, VFR conditions will return at all terminals by
Saturday afternoon as the low stratus deck lifts and only FEW/SCT cu
will roam the sky to round out the forecast period. Winds will
continue to pull out of the north-northeast through tonight before
gradually toggling to a south-southwesterly component by peak
heating Saturday.

Outlook: Convection and possible restrictions will linger into early
Saturday in eastern areas. Isolated/widely scattered diurnal showers
and thunderstorms are expected Sat through at least the first half
of next week...mainly over the mtns.

&&

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

&&

$$

SYNOPSIS...TW
NEAR TERM...AR/CAC
SHORT TERM...TW
LONG TERM...TW
AVIATION...CAC