Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
099
FXUS62 KGSP 292323
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
723 PM EDT Tue Jul 29 2025
.SYNOPSIS...
The heat wave will gradually abate through Thursday into Friday
as the upper pattern slowly shifts and brings a cold front down
from the north. The front will bring some much-needed relief from
the heat in the form of below normal temperatures this weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 150 PM EDT Tuesday: Mid-level ridge will be in the midst
of breaking down over the southeastern CONUS through much of the
period as the center of the 597+ dm ridge drifts westward into the
Southern Plains. A subtle weakness in heights and scattered vort
energy will help set the stage for diurnally driven convective
initiation over the higher terrain and even east of the mountains,
which is evident across central NC. The weird part of the pattern
today shows a weak area of low-pressure over southern Georgia and
Florida Panhandle. The mean wind is oriented east to northeasterly
as a result, which will drive the convection in central NC to move
from east-to-west, instead of the opposite. CAMs support this trend
and with the added forcing for ascent aloft from the vort energy,
convection may linger into the early overnight hours, especially in
regions that are left untapped. Current mesoanalysis environment
supports 2000-3000 J/kg of SBCAPE, 600-1000 J/kg of DCAPE, and
very little in the way of deep layer shear (<20 kts). With PWAT
values =>2.00" east of I-26 and between 1.75"-2.00" west of I-26,
expect heavy rainfall rates leading to excessive runoff to cause
localized hydro issues as the relatively slow storm motion will
support this notion. Can`t rule out a few strong to severe storms,
with wet microbursts being to main threat as typical pulse storm
mode is expected. Otherwise, heights are still very warm across
the region and dewpoints haven`t fully mixed out, so afternoon
highs still top out in the mid-90s outside the mountains, with heat
indices still climbing to Heat Advisory criteria levels. Dewpoints
are in the mid-70s across a good portion of the advised area, so
the current Heat Advisory that is out until 8:00PM this evening
is still on track.
Lingering cloud debris and good coverage in convection will lead
to a very saturated low-level airmass across the CFWA overnight
tonight. Very low dewpoint depressions and weak low-level
nocturnal inversion should set the stage for low stratus and fog
to develop. Guidance has been hitting this all morning and in
response, overnight lows will remain in the mid-70s outside of
the mountains and upper 60s to low 70s in the High Country. If
enough clearing can get going overnight, a few patches of dense
fog can`t be ruled out, especially in the major mountain valleys.
The temperature trend has lowered for Wednesday, which is likely due
to the slower scattering of the low stratus deck in the morning and
the earlier convective initiation in the mountains. The environment
will be relatively the same as today, with a little less time to
destabilize due to the lingering cloud cover. CAMs continue to
show ridgetop and Blue Ridge Escarpment initiation in the early
afternoon hours and wouldn`t be surprised to see differential
heating boundary initiation outside of the mountains as well. In
this case, afternoon highs return to near-normal values. While heat
indices still reach triple digits in some locations as dewpoints
will be in the low to mid-70s, a Heat Advisory may not be needed
across the CFWA and if needed, the product would likely reside to
locations south and east of I-85.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 104 PM EDT Tuesday...the big story for the week will be the
end of the recent heat wave as the upper pattern gradually shifts
through Thursday and Friday. The main driver will be the slowly
amplifying mid/upper trof over eastern North America in the latter
part of the week that will slowly push an ill-defined sfc frontal
zone down across the Carolinas. Many times such a change in air
mass would be more dramatic, but this time the guidance suggests
a more lengthy transition and less of a chance of severe storms
along the boundary, with only modest amounts of buoyancy and little
shear. The slow moving boundary is more favorable for heavy rain
given relatively high precipitable water, deep warm cloud depth,
and expected slow storm movement, so we will have to keep tabs on
the flash flood potential, particularly Friday if the front gets
hung up across the area during the day. The good news is that many
places could use some rain, and most places will see a drop off in
high temperatures both days that should keep us from reaching Heat
Advisory criteria. Friday is probably the most tricky day because
temps will depend on where/if the front hangs up and if that results
in widespread precip/clouds that could keep temps on the cool side
of normal. The front is expected to sag south of the forecast area
by daybreak on Saturday, bringing a welcome end to the heat.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 122 PM EDT Tuesday...if all goes according to plan, Saturday
is going to feel a lot different around these parts, as a weak
sfc high starts to ridge down from the Great Lakes across the
region with cooler air and a northeasterly flow that supports
keeping clouds and scattered to numerous showers across the area
due to some low level isentropic upglide. The guidance blend looks
intriguing with high temps staying about ten degrees below normal
Saturday, though confidence in temps actually ending up that cool
is not especially high. A lot can still happen to keep it from
being that cool. That being said, by Sunday the pattern becomes
more indicative of a summertime wedge, with a parent high off the
New England Coast that keeps a shallow and stable air mass over the
area east of the mtns, even though the low level isentropic support
for clouds diminishes and moves off to the southwest. Confidence
is better in the below normal temps that day. Although the parent
high weakens and moves off Monday, the remnant cool air mass will
take some time to modify so temps will stay below normal. Finally,
by Tuesday, the wedge should have been completely drained, but
a short wave digging into the eastern trof will allow temps to
return only close to normal while increasing our precip chances
again. How short-lived this summer break will be remains to be seen.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Showers and thunderstorms continue this
evening across the area before tapering off before midnight,
especially in the mountains. A TEMPO for TSRA through 02z at KAVL as
thunderstorms have become more numerous. Once the TSRA fades, all
sights should become VFR through at least most of the overnight
hours. Low stratus is expected to form at most sites and could
affect vsby in the early morning hours. KAVL could see IFR before
sunrise, before scattering. Other sites could also have brief MVFR
vsby given the rain that fell earlier. Winds overnight should become
calm to VRB and pick up again Wednesday morning out of the NE and
toggle more SE through the TAF period. Another round of afternoon
TSRA is possible so PROB30s for all terminals.
Outlook: Scattered showers and thunderstorms each afternoon through
Saturday. Low stratus and/or fog is possible each morning,
especially in the mountain valleys.
&&
.CLIMATE...
RECORDS FOR 07-29
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 98 1952 67 1984 74 1877 55 1911
1895
KCLT 103 1952 72 1984 77 1993 59 1920
KGSP 104 1952 70 1984 76 1949 59 1911
1936
RECORDS FOR 07-30
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 93 1954 68 1936 72 2011 54 2014
1878 1897
1895
KCLT 101 2011 71 1981 77 1953 58 1914
1941
KGSP 101 1999 73 1981 77 2011 60 1914
1911
1884
RECORDS FOR 07-31
MAX TEMPERATURE MIN TEMPERATURE
STATION HIGH LOW HIGH LOW
------- ---------- ---------- ---------- ----------
KAVL 95 1999 65 1936 71 2011 53 1986
1914
KCLT 100 1999 69 1936 77 1941 56 1914
1931 1931
1915
KGSP 104 1999 71 2014 78 1999 56 1936
1931
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 8 PM EDT this evening for GAZ018-026-028-
029.
NC...Heat Advisory until 8 PM EDT this evening for NCZ036-056-057-
068>072-082-508-510.
SC...Heat Advisory until 8 PM EDT this evening for SCZ008>014-019-
104>109.
&&
$$
SYNOPSIS...PM
NEAR TERM...CAC
SHORT TERM...PM
LONG TERM...PM
AVIATION...CP
CLIMATE...