798
FXUS62 KGSP 131753
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
153 PM EDT Sat Jul 13 2024

.SYNOPSIS...
Hot high pressure will dominate the area into early next week, with
only isolated showers and thunderstorms each afternoon. The pattern
is expected to change mid-week as a cold front stalls across the
area and brings above normal rain chances and cooler weather.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 140 PM EDT Saturday: Garden variety convection beginning to
pop up in parts of the area, mainly over the BR Escarpment and Upper
Savannah River Valley. Updated PoPs to reflect the current radar
trends. Not expecting this activity to produce strong to severe
storms, but a slight uptick in coverage is possible as we enter the
peak heating of the day.

Otherwise, a broad, low-amplitude long wave trough will remain
centered west-through-north of the forecast area through the period.
Weak subsidence and mid/upper level drying is anticipated in the
wake of a disturbance that will lift away from the NC/ Mid-Atlantic
coast today. As a result, forecast soundings are generally capped,
albeit modestly unstable this afternoon. As such, convection-
allowing models limit diurnal convective development to rather
spotty activity over the mountains and foothills. PoPs are limited
to 20-30% in these areas, with <20% chances across much of the
Piedmont. Chances for severe storms are practically non-existent,
and in fact thunder may be difficult to come by this afternoon,
while the drier atmosphere will also limit the heavy rainfall
potential. Max temps are expected to be around 5 degrees above
normal in most locations, but deep mixing is expected to limit the
potential for reaching the Heat Advisory criteria of 105, but some
locations across the lower elevations of the Piedmont could reach
the century mark for an hour or two this afternoon. Any convection
should diminish quickly this evening, giving way to a warm overnight.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 155 AM Saturday: 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. The CWA remains in a
pattern of high pressure during the short term, keeping the area
relatively dry and hot. Sunday looks dismal in terms of any precip
chances. Sounding guidance has a batch of mid-level dry air atop a
modest temperature inversion. Even if precip could form in the
afternoon, the boundary layer has such a stout T/Td spread, anything
that does fall through that layer should evaporate. The GFS and EURO
do indicate an uptick in moisture with PWAT profiles reaching the
1.5-1.75 inch range east of the mountains, but this will not
suffice. Rinse and repeat with very similar environmental parameters
on Monday. Nothing of note with winds either, as the pattern remains
in a very broad, stagnant summertime pattern. 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 on Sunday. Monday could have a few areas in the eastern NC
Piedmont approach 105 degree heat index values. Confidence is
increasing on this given the strong height rises and persistent high
pressure.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 205 AM Saturday: By Tuesday, high pressure continues to
dominate the lower CONUS and keeps the area dry for the most part.
Long term guidance shows little QPF response as a small signal over
the mountains on Tuesday afternoon and to the south by the overnight
hours. Again, similar to Monday, 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 given such
strong chances for evaporation. 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. A stronger cold front could make its way toward the CWA
and stall by the end of the week. This pattern could create higher
chances for more rainfall over multiple days. At the surface,
amplifying high pressure off the east coast should setup a
persistent SW flow and moisture advection into the area. But, as
always, this is far out in the forecast time and will likely change.
As for temperatures, Tuesday still 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 as model guidance has
trended more toward an increase in moisture content, especially east
of the mountains. Heat index values of 105 are possible and
confidence is increasing on this. Wednesday could also see another
day of hot temps and similar heat index values of the day prior. The
cold front looks to approach the CWA Wednesday night into Thursday,
which should provide some heat relief to much of the area.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: VFR conditions are expected through the
forecast period. Low-end VFR cu beginning to settle over most of the
area, with isolated showers popping up. Decided to include a VCSH
mention at KAVL through 01Z based on current radar observations and
latest model trends. Also, included a TEMPO for -SHRA and associated
restrictions at KAND through 21Z due to a few showers developing
within 10 nautical miles of the terminal. Otherwise, confidence is
too low for a SHRA/TSRA mention at the other TAF sites as the
coverage will remain isolated. Winds continue to toggle mostly south
to southwesterly through the evening before going light and variable
overnight with mostly clear skies. Can`t rule out mountain valley
fog and fog near bodies of water, but confidence is too low for a
TAF mention at KAVL/KHKY/KAND at this time. Wash, rinse, and repeat
for Sunday as isolated diurnal SHRA/TSRA will be in store with
afternoon VFR cu and winds continue to run southwesterly.

Outlook: Isolated/widely scattered diurnal showers and storms are
expected mainly over the mountains early next week. Shower and
thunderstorm are expected to increase during the latter half of the
week as a cold front pushes into the region. Morning fog/low stratus
will be possible each morning, especially across the mountain
valleys and for areas that received heavy rainfall the day prior.

&&

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

&&

$$

SYNOPSIS...TDP
NEAR TERM...CAC/JDL
SHORT TERM...CP
LONG TERM...CP
AVIATION...CAC