699
FXUS62 KGSP 061401
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1001 AM EDT Sat Jul 6 2024

.SYNOPSIS...
A weak surface boundary will move in from the north and become
stationary near the southern portion of the forecast area today.
This front will increase the chance for thunderstorm activity
outside the mountains through Sunday. More typical summertime
thunderstorm development returns Monday and persists through next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 953 AM Saturday: A few areas of morning fog and low stratus,
especially across favored mountain valleys, has since mixed out and
lifted following sunrise. The main feature of note this morning is a
weak frontal boundary dropping across the area. As of this writing,
the boundary was located roughly along I-85 where winds have shifted
to out of the north/northeast. Dewpoints have fallen into the upper
60s to low 70s behind the boundary with mid to upper 70s to the
south. The front is expected to stall in the vicinity of I-85, but
could edge a little farther southeast. As such, the low-level ThetaE
axis has shifted east along with the higher PWATs near 2". Thus,
afternoon showers and storms will be confined predominately along
and south of I-85 within the richer boundary layer moisture plume.
Have tweaked PoPs accordingly with lowering behind the boundary and
a slight increase across far southeastern portions of the area.
Moderate instability could support a few deeper cores, but poor near
moist adiabatic lapse rates will generally preclude a threat for
severe storms outside of a couple isolated wet microbursts. Moisture
pooling ahead of the boundary will support heat indices near 105
degrees and the ongoing heat advisory still appears well placed, but
will ultimately hinge on exact placement of the front and how much
moisture mixes out. Thus, will let the advisory ride as is.

Otherwise, little change in the upper level pattern, with a
broad upper trough axis across the middle of the CONUS and WSWLY
flow atop the forecast area. A sfc front will stall out roughly
along I-85 today or slightly SE of there and becoming a focus
for convection this aftn. Low-level thicknesses will be down a
tad from yesterday, but with the day starting out mostly sunny,
expect another day with above normal temps. Dewpts are not
likely to mix out as much today, so despite highs being "only"
in the mid 90s, heat index values will once again approach 105
across the southeastern tier of our counties. A Heat Advisory
was issued from 11 am to 8 pm today from Elbert County to Union,
NC. Convection will likely start bringing the heat down this aftn,
so parts of the advisory may be able to be canceled early. As for
convection, guidance is in good agreement on the highest coverage
being across the southeastern third of the forecast area. Less CAPE
across mountains will make for mainly showers and weak storms. But
cannot rule out a strong to severe storm in the lower Piedmont,
where the CAPE will be highest. Shear will be weak and a lack of
mid-level dry air will limit DCAPE for strong wind gusts.

Convection should diminish this evening, but plenty of cloud cover
may linger thanks to the stalled front. Patchy fog may develop
where skies manage to clear, and lows will be slightly above normal.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 120 AM Saturday...Upper ridging remains dominant thru the
period while an h5 trof has trouble building east out of the
Midwest. This will maintain a stagnant airmass over the FA while Atl
ridging continues to pump in a good amt of moisture. Soundings still
show PWAT values well abv normal, arnd 2.25 inches, each day as mlvl
dry air advec will be negligible. A sfc bndry remains trapped east
of the mtns in this pattern and looks to be a good focusing zone for
early onset convec each afternoon. The NAM/GFS profiles indicate a
deep warm cloud layer and CCLs being reached rather early...likely
by noon Sun. So, will expect decent coverage of showers and
thunderstorms once again likely continuing into the early overnight.
A similar setup on Mon, with maybe a little more dry air aloft. The
severe potential will remain a little elevated as several storms may
be able to develop wet microbursts. High precip rates along with
weak steering flow, may lead to isol hydro issues as storms could
train along the ern bndry and possibly anchor over a few mtn
ridgetops for a while. Highs will remain near normal, with lows held
abv normal by a few degrees due to the moist column.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 155 AM Saturday...Not much change made to the ext range fcst.
The period looks to remain convectively active  as deep moisture
levels remain high and warm sfc temps allow for sbCAPE values arnd
1000-1200 J/kg each afternoon. The models are shifting the upper
ridge axis a little further east as energy from a mid/lat trof
begins to work into the area, which would increase the potential of
severe storm development each afternoon, esp as the mid levels dry
out a little more. Still looking more like a damaging wind threat
per profiles, but weak column flow could lead to localized hydro
issues even with PWATS reducing a little. The guidance is a little
shaky with the inclusion of vort energy and added moisture from the
remnants of TC Beryl Thu into Fri...but if this scenario pans out it
could portend to a better chance of hydro issues across the NC mtns
during this timeframe. Max and min temps will remain near normal
levels each day in a relatively stagnant airmass.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Patchy fog and low stratus has developed
over or around KAVL/KAND/KHKY this morning, and that should burn off
within the first hour or so of the 12z TAFs. Later today, convection
is expected to fire again across the area, with greatest coverage
across the Piedmont due to a stalled frontal boundary. Peak timing
looks to be the typical mid-aftn thru early evening hours. Have a
tempo for TSRA at all sites. Winds will be quite variable today, but
are expected to favor a S/SW direction across the Piedmont and N/NW
at KAVL. The boundary will begin to lift north slightly tonight,
with moist SE flow possibly allowing some fog and stratus to form
across the area early Sunday morning. Confidence is increasing on
IFR restrictions at most, if not all, our TAF sites by 12z Sunday.

Outlook: An active summertime convection for most of next week,
leading to scattered to numerous showers and thunderstorms and
possible restrictions each afternoon/evening. Fog or low stratus
may develop each morning, especially over areas that received rain
the previous day.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 8 PM EDT this evening for GAZ029.
NC...Heat Advisory until 8 PM EDT this evening for NCZ071-072-082.
     Heat Advisory until 11 AM EDT this morning for NCZ070.
SC...Heat Advisory until 8 PM EDT this evening for SCZ009-011>014-
     019.
     Heat Advisory until 11 AM EDT this morning for SCZ008-109.

&&

$$

SYNOPSIS...SBK
NEAR TERM...ARK/TW
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...ARK