219
FXUS62 KGSP 131041
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
641 AM EDT Sat Jul 13 2024

.SYNOPSIS...
Drier conditions return this weekend, lingering into early next week
as high pressure builds across the area. Hot weather returns to
start the week through Wednesday. The pattern changes mid-week into
as a cold front stalls across the area and brings above normal rain
chances and cooler weather.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 640 am Saturday: 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 FRIDAY/...
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 /12Z SATURDAY THROUGH WEDNESDAY/...
***AMD NOT SKED continues in the KHKY TAF for this cycle due to the
ongoing ASOS comms outage and the potential for restrictions this
morning.***

At KCLT and elsewhere: IFR cigs continue at KCLT this morning,
although the terminal is right on the back edge of the cloud deck.
Clouds should clear the terminal rather quickly this morning, with
VFR expected by 14Z. Meanwhile, localized VLIFR cigs have developed
at KAVL, and these too should last no longer than 14Z. Otherwise,
VFR conditions are expected through the period. Deep convection is
should develop this afternoon...esp across the mountains, but
overall coverage is expected to be rather spotty...and tending more
toward SHRA than TSRA, so will continue to omit any mention in the
TAFs at this time. General light & variable/calm or light NW winds
will continue...likely returning to light SW at most sites during
the afternoon and evening and remaining through the end of the
period.

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