245
FXUS62 KGSP 120730
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
330 AM EDT Fri Jul 12 2024

.SYNOPSIS...
A weak tropical low will move inland over the eastern Carolinas on
Friday, increasing rainfall chances for areas along and east of
Interstate 77. Dry weather returns for the weekend and into the
beginning of next week, with a pattern change mid week possible.
Above normal temperatures through the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 310 am Friday: A weak disturbance near the Carolina Coast is
expected to retrograde a bit and become absorbed in the general
troughy upper pattern over the East this morning. This will result
in subtropical moisture...precipitable water values approaching 2"...
to surge into the eastern portion of our CWA later in the morning,
resulting in thickening cloud cover and increasing convective
chances. In fact...a few showers are already impinging on the
eastern border of the forecast area early this morning. Coverage and
intensity of convection should slowly increase throughout the day,
as the atmosphere destabilizes to the tune of ~1500 J/kg of sbCAPE
across the eastern half of the area by late afternoon. Additional
shower activity and perhaps a thunderstorm or two should also
initiate over the high terrain during mid/late afternoon. While much
of the area will see 20-40 PoPs, locations east of I-77 should see
sufficient afternoon coverage to warrant likely probabilities. Only
the upper Savannah River Valley/western Upstate are expected to be
largely void of convection today. Instability is expected to be a
bit too meager to support a severe storm threat, but locally
heavy/perhaps excessive rainfall will be possible across eastern
areas in the very moist conditions. Max temps will range from a
little below normal across the I-77 corridor and vicinity, to a
little above normal west of I-26. Convective chances dwindle this
evening to little more than token slight chances across the east
after midnight. Min temps are expected to be a couple of degrees
above climo.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 155 AM Friday: Continuing the summertime pattern with more
heat and less rain. Synoptically, The majority of the CONUS remains
under high pressure, including the southeast. The Bermuda high off
the east coast churns and amplifies into Sunday as does the
persistent anti-cyclone over the southwest. Essentially, the CWA is
caught in the middle of two dominating areas of high pressure,
keeping the area relatively dry and hot. Saturday, a swath of 2 inch
plus PWATS remains centered just to the east of the CWA. Guidance
from the GFS signals around 1.5 inch PWATS on the eastern fringe,
upticking the moisture and heat index in this area. QPF response,
however, is dry. Modeled soundings indicate a strong mid-level
inversion and dry layer, hindering any notable rainfall. Even if
something could form, the boundary layer is also relatively dry
given the stout inverted-V shape. Sunday is a similar story, but
with less of a mid-level inversion present. This is driven by higher
moisture content east of the mountains due to the SW surface flow.
Modeled soundings also indicate better mid-level CAPE and a return,
but again, rain chances are minimal as QPF response is non-existent.
As for any heat index concerns, moisture return is slow and helps to
keep values around the low 100s for a few areas south of I-85 and
east of the I-77 corridor. Overall, hot and dry for the short term.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 200 AM Friday: The extended term starts off similar to how the
short term ended, with a pattern change possible by mid week. Monday
and Tuesday, high pressure continues to dominate the lower CONUS and
keeps the area dry for the most part. Long term guidance shows
little to no QPF response Monday and a small signal over the
mountains on Tuesday afternoon. Again, both days have similar
modeled soundings with abundant mid-level dry air and an inverted-V
in the boundary layer. Confidence for any rain during the beginning
of the week is very low. However, a pattern swing by mid-week could
be in the works. Long range guidance from the GFS/EURO signal a
developing upper low and trough across Canada, north of the Great
LAkes. This amplification could lead to height falls across the
eastern portion of the CONUS, and spilling into the CWA starting
Wednesday. At the surface, amplifying high pressure off the east
coast should setup a persistent SW flow and moisture advection into
the area. This could start the unsettled pattern with an increase in
PoPs, especially over the mountains, through the end of the period.
At this time, Thursday and Friday could be the wetter days, but will
likely change as the forecast nears. As for temperatures, Tuesday
looks to be the hottest day with actual temps reaching triple digits
across most of the CWA east of the mountains. Heat index could be a
concern, but with dewpoints mixing out during the day, confidence on
high heat indices over 105 is low at this time. After Tuesday, temps
look to decrease given the height falls aloft, which should provide
some heat relief to much of the area.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR conditions are forecast at most sites
through the period. The only exception will be at KCLT, as sub-
tropical moisture is expected to surge into the area later this
morning in association with a developing disturbance near the coast.
While low VFR cigs are expected to develop as a consequence, periods
of MVFR are possible throughout the day, with those chances
increasing later tonight into early Sat. Shower and thunderstorm
chances will also increase in the KCLT area from late morning
through the afternoon. Tempos for TSRA may be warranted eventually,
but for now, confidence in timing and convective coverage is such
that VCSH and Prob30s for TSRA will suffice for now. Showers and
storm chances droop off sharply west of KCLT...a Prob30 for -TSRA is
carried at KHKY during the afternoon, but coverage near KAVL and the
upstate SC terminals is expected to be more isolated. Winds will
generally favor light NE through the period.

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...CP
NEAR TERM...JDL
SHORT TERM...CP
LONG TERM...CP
AVIATION...JDL