Clemson, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

932
FXUS62 KGSP 281751
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
151 PM EDT Mon Jul 28 2025

.SYNOPSIS...
Oppressive heat and humidity persist through Thursday, with
dangerous heat indices expected east of the mountains. Isolated to
widely scattered afternoon showers and Thunderstorms are expected
through Wednesday. A cold front will boost shower and thunderstorm
chances toward the end of the workweek as well as bring some much-
needed relief from the heat in the form of below normal high
temperatures this weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 1252 PM Monday: We were expecting the coverage of convection
to be better than it has been over the past several days, and so
far the atmosphere has not disappointed us. Scattered showers
and storms have already formed across the area basically along
and west of I-26, while numerous storms were noted over northeast
TN headed for the mtns. The environment holds 2000-3000 J/kg of
sfc-based CAPE and that should persist into the afternoon where
storms don`t consume it. The threat of severe storms looks modest
because of poor lapse rates, but there`s enough mid-level dry air
to give us a dCAPE of around 800 J/kg with weak shear. That should
be enough to support some wet microburst action here and there, so
a few severe wind gust producers won`t be ruled out. Storms appear
to be moving along just enough to lessen some of the flash flood
potential, but some storms near the Escarpment were showing some
signs of anchoring. The somewhat earlier than expected development
of the deep convection might help to keep temps a few degrees
cooler than expected this afternoon, but no changes were made at
this point to the high temp fcst or the Heat Advisory.

The convection may or may not continue well into the evening hours,
depending on which of the CAMs you like best. Most of the CAMs
have the better coverage this afternoon and then kill it off around
sunset, while the HRRR is alone in developing better coverage this
evening. The fcst more or less splits the difference for now, and
holds onto a chance of storms into the late evening in deference
to the consistency shown by the HRRR this evening. Either way,
eventually we should get to a quiet overnight period with a better
potential for valley fog than last night.

Otherwise...the thought (hope?) is that our hottest days are past us
after today. The upper anticyclone centered over the Ozark Plateau
today is still expected to drift southwestward over the next 24
hours and a weakness in the upper ridge will continue to develop
over the Carolinas. For Tuesday, the guidance blend supports
keeping the dewpoints slightly higher which allows the guidance
to show better sfc-based buoyancy with less of a potential for a
cap, thus even better coverage of showers and storms even earlier
in the day. More pulse severe storms are possible with the usual
threats. As for highs...whereas the last several days the blend
was a few degrees on the low side, there`s more of a potential for
the highs Tuesday to be a degree or two too hot in some locations,
balanced out by the higher dewpoints to keep the apparent temp still
close to the 105 deg threshold. We already have a Heat Advisory
in effect for Tuesday afternoon/eve and that won`t be changed at
this point, even though it could ultimately prove to be overdone.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 100 PM EDT Monday...

Key Messages:

1) Heat Wave Continues with Heat Advisory Criteria Possible Each
Afternoon East of the Mountains

2) Heat Index Values from 100 to 105+ Degrees F During Peak Heating
Each Day East of the Mountains

3) Better Coverage of Shower and Thunderstorms Expected

The hot upper anticyclone continues breaking down over the forecast
area Tuesday evening into Wednesday before getting shunted southward
Wednesday evening into Thursday as a potent upper trough digs across
the Northeast. At the sfc, a cold front will gradually approach out
of the N/NNW throughout the day Thursday bringing better chances for
convection ahead of it. The bad news is that both the heat and
humidity will stick around through the short term. The good news is
that the heat and humidity will be on a downward trend each day.
However, Heat Advisory criteria (which starts at 105 degrees F) will
remain possible east of the mountains each day during peaking
heating, mainly along/near I-77 and the Upper Savannah River Valley.
So, additional heat advisories may be needed for these locations but
confidence is low with coverage of convection expected to increase
through the short term (which could limit heat index values). NBM
has the highest PoPs (60%-90%) across the western two-thirds of the
CWA on Wednesday, with the highest PoPs (60%-90%) along and north of
I-85 on Thursday. Could see convection linger ahead of the front
through the late evening/early overnight hours through the period
and the NBM PoP trend reflects this potential well. Any severe
threat continues to look low through the period but a few strong,
sub-severe storms cannot be entirely ruled out each afternoon and
evening. There will be more of a concern for locally heavy rainfall
leading to isolated flash flooding issues through the short term
with PWATs above the 90th percentile for this time of year (ranging
from 1.75"-2.5").

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 100 PM EDT Monday...

Key Messages:

1) Much Cooler and Below Normal Highs Return Behind a Cold Front
Friday into Early Next Week to Kick Off August

2) Shower and Thunderstorm Chances Linger through at least the First
Half of the Weekend

3) Cold Air Damming May Bring Drier Conditions Sunday into Monday

Potent upper troughing continues digging southward, ending up over
the Southeast this weekend and early next week. At the sfc, a cold
front will push across the forecast area late Thursday into early
Friday keeping convective chances around as well as ushering in
colder air behind it. Cold air damming will develop this weekend,
lingering into early next week as a sfc high builds over the
Northeast. Highs on Friday will end up a few degrees below normal
for most locations, becoming a few to several degrees below normal
for all locations this weekend into early next week. Highs each
afternoon east of the mountains will struggle to get out of the
upper 70s and lower 80s Saturday into Monday.

As for convection....global models generally agree that shower and
thunderstorm chances will linger through at least Saturday before
drier conditions return with the wedge Sunday into Monday. Thus, the
NBM likely to categorical PoPs (60%-90%) across the forecast area
Friday into Friday night look reasonable. The NBM depicts slightly
lower PoPs (40%-70%) on Saturday as the wedge begins to build into
the region which is in fairly decent agreement with the latest
GFS/ECMWF. The NBM then holds onto chance PoPs Sunday into Monday
and this appears reasonable given that confidence on completely dry
conditions towards the end of the period is low at this time.
Although wind shear will increase slightly on Friday, thick cloud
cover and rain will both act to limit destabilization during peak
heating. Thus, the severe weather threat continues to look low for
now. The bigger concern will be regarding heavy rain Friday into
Saturday, especially for areas that received heavy rain during the
short term forecast period. PWATs will remain elevated and above the
90th percentile for this time of year through Friday night, and
possibly into Saturday for some locations, before CAD brings drier
air (and thus lower PWATs) Saturday into Monday. Thus, the threat
for isolated flash flooding will continue the first half of the
period.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Showers and thunderstorms are getting
more and more numerous across the region this afternoon, with
coverage greater than expected from the morning run of the CAMs. All
terminals will get either a TEMPO right way where storms are already
in close proximity, or a TEMPO later in the afternoon, or in the
case of KCLT where confidence is the least, a PROB30. Restrictions,
mostly low vis, will be carried in the TEMPO/PROB30 groups. Wind
should stay light N to NE away from thunderstorm outflows. After the
convection wanes late this evening, only convective debris clouds
remain. KAVL has the best chances for a fog/low stratus condition
in the pre-dawn hours Tuesday, mostly because low temps will be
so warm across the region. For Tuesday, even better coverage of
thunderstorms is expected with a slightly earlier start, but we
will keep that out of the forecast for now as the terminals may
not be affected until the last hour or two of the period, but most
likely after 18Z.

Outlook: More convectively active weather is expected to continue
thru the work week, with numerous to widespread diurnal convection
in the mountains, and scattered to numerous convection in the
Piedmont, especially later in the week. Low stratus and/or fog
will be possible each morning...mainly in the mtn valleys.

&&

.CLIMATE...
RECORDS FOR 07-28

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      98 1952     68 1890     70 2010     53 1895
                                        1878
                                        1877
   KCLT     102 1952     70 1890     78 2016     54 1962
   KGSP     103 1952     72 1926     76 2016     60 1911
                                        1936        1904



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.
     Heat Advisory from 11 AM to 8 PM EDT Tuesday for GAZ018-026-
     028-029.
NC...Heat Advisory until 8 PM EDT this evening for NCZ035>037-056-
     057-068>072-082-508-510.
     Heat Advisory from 11 AM to 8 PM EDT Tuesday for NCZ036-056-
     057-068>072-082-508-510.
SC...Heat Advisory until 8 PM EDT this evening for SCZ008>014-019-
     104>109.
     Heat Advisory from 11 AM to 8 PM EDT Tuesday for SCZ008>014-
     019-104>109.

&&

$$

SYNOPSIS...AR
NEAR TERM...PM
SHORT TERM...AR
LONG TERM...AR
AVIATION...PM
CLIMATE...