Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
654 PM EDT Mon Jul 26 2021

.SYNOPSIS...
A weak cold front will move south across our area tonight and
Tuesday.  This will result in scattered to numerous showers and
thunderstorms with a few locations getting excessive rainfall in a
short time.  Expect drier and hotter conditions Wednesday through
Friday with high temperatures feeling like 100 degrees in the
piedmont.  A weak cold front will drop south this weekend cooling
temperatures to near normal.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 640 PM EDT Monday: The overall forecast is still on track as
an apparent frontal zone continues to march through the area. With
better-than-normal shear parameters, a loosely organized line of
convection is pushing through locations south of I-85 after making
its presence felt in areas along and north of the I-85 corridor
earlier today. Expect stratiform precip to continue behind the main
band of convection and should linger into the early overnight hours
before waning off. Mountain valley fog/low stratus will be possible
overnight and around daybreak. Fog/low stratus chances will spread
east of the mountains as well from the widespread coverage of
rainfall.

Ridging remains entrenched over the western U.S. with modest
troughing over the Eastern Seaboard. The wind maximum is well to our
north, with the Carolinas situated beneath a comparatively relaxed
wind pattern. Meanwhile, a persistent Bermuda high sits over the
western Atlantic, and continues to dominate surface flow, pumping
moisture into areas east of the Appalachians. A weak shortwave
crosses the region this afternoon, inducing minor height falls and
providing weak QG forcing. At the surface, the attendant cold front
is already crossing the CWA, generating convective activity as it
encounters moderately-unstable, moisture-rich air across the
foothills. PWATs exceed 2" across much of the Piedmont/Upstate in
the wake of several days' worth of southerly flow and moisture
advection off the Atlantic coast, so convection should have no
trouble continuing well into this evening. CAMs favor increased
SBCAPE toward the south, over the southern Appalachians, SC Upstate
and perhaps the southern Piedmont of NC.

Slightly higher-than-anticipated effective shear across the
Carolinas means that a few stray severe cells cannot be ruled out,
but as convection continues, the primary threat will be heavy
rainfall. MBE velocities won't exceed 5kts, and warm cloud depth
will crest 12 kft for several hours. The HREF's probability-matched
mean depicts upwards of an inch of QPF in some spots across the
Upstate, and accordingly the WPC has placed the entire CWA under a
marginal risk for excessive rainfall.

Heights may tick up a tad on Tuesday, but with the weakening
boundary stalling along or south of the I-85 corridor, we'll retain
the risk of widespread showers, especially across the southern
tier of our counties.  CAMs suggest there will be a lull in precip
overnight tonight as upper forcing diminishes, before a rebound in
instability in the early afternoon tomorrow allows convection to
begin firing off again.  With SBCAPE values potentially exceeding
2500 J/kg, warm cloud depths at least 10-11 kft, and afternoon
LFCs even a bit lower than today's, convection will once again
be widespread, and these cells be will rain-producers similar to
today's. The entire CWA remains in the WPC's marginal risk for
excessive rainfall tomorrow. While confidence remains low on the
exact coverage and behavior of tomorrow's convection, the CAMs agree
that the most intense activity should have moved to our south and
east by late Tuesday evening, though scattered showers will likely
linger across the Upstate and perhaps the Southern Piedmont through
the end of the near term.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 245pm EDT Monday:  After rain trails off Tuesday night,
temperatures rebound on Wednesday following the clouds and rain that
kept temperatures in check on Tuesday.  Mid-90s are expected over
most of the foothills and Piedmont areas, and 80s to near 90 in the
mountains.  Weak FROPA on Tuesday only drops surface dewpoints a few
degrees over the mountains, and with continued high humidity, heat
index values will be on the sultry side a few degrees above observed
temperatures.  MLCAPE and convective forcing both are much reduced
Wed. and Thurs, and PWATs drastically decline to around 1.5" on
Wednesday, with low chances of rain or thunder.

General northwest flow aloft continues through Thursday and beyond
with weak surface high pressure giving light and somewhat variable
winds.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 2:45pm EDT Monday:  General northwest flow continues through
the extended with generally weak and variable surface winds and
occasional shortwave passages that enhance the chances for afternoon
thunder.  Persistent ridge keeps the central CONUS in its grip, with
a deep upper trough over the eastern half of the CONUS. There is
some chance for thunder, mostly in the afternoons, each day, with
the best chance for enhancement Saturday or Sunday as eastern CONUS
trough deepens considerably as it is reinforced by a large shortwave.

Temperatures across the area remain seasonally warm to hot, a few
degrees above normal, with slight cooling towards the end of the
week as eastern CONUS trough deepens.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Most of the convection from earlier has
shifted south of the terminals with the exception of KAND. Lingering
showers and embedded thunder will be possible through the early
overnight hours, but shouldn't cause much in the way of flight
restrictions. However, there is increased confidence in the
development of IFR restrictions at KHKY, and LIFR restrictions at
KAVL owing to the development of fog/low stratus in the hours before
sunrise. All other sites remain VFR/MVFR into the morning with IFR
potential due to the copious amounts of rainfall received today. We
should see scattered showers and storms Tuesday afternoon again, but
confidence is low enough on the timing and coverage to simply carry
VCSH and a few PROB30s. Winds will be mainly light and variable
tonight, while becoming S to SW at most TAF sites Tuesday.

Outlook: With the frontal boundary gradually becoming more diffuse
past Tuesday evening, drier air filters into the area and results in
a lull in activity Wednesday and Thursday. Diurnally-drive
pulse thunderstorms should pick up again on Friday, along with a
chance for fog and low stratus Friday and Saturday morning.

Confidence Table...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       High  95%     High  83%     Low   54%     High 100%
KGSP       High 100%     High  83%     High  86%     High 100%
KAVL       High 100%     High 100%     Med   72%     High 100%
KHKY       High 100%     High  83%     High  86%     High 100%
KGMU       High 100%     High  83%     High  86%     High  94%
KAND       High 100%     High 100%     High  95%     High  94%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:

www.weather.gov/gsp/aviation

&&

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

&&

SYNOPSIS...DEO
NEAR TERM...CAC/MPR
SHORT TERM...WJM
LONG TERM...WJM
AVIATION...CAC/MPR

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
405 AM EDT Mon Jul 26 2021

NCZ036-037-057-270815-
Iredell-Davie-Rowan-
405 AM EDT Mon Jul 26 2021

This Hazardous Weather Outlook is for piedmont North Carolina.

.DAY ONE...Today and tonight.

A backdoor cold front will allow for shower and thunderstorm
development this afternoon into this evening. The main hazards are
cloud- to-ground lighting, isolated strong to severe storms bringing
the potential for damaging wind gusts, and heavy downpours. Any
areas that repeatedly see heavy downpours could experience excessive
rainfall leading to the potential for isolated flooding or flash
flooding.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-028-029-NCZ033-035-048>053-056-058-059-062>065-
068>072-082-501>510-SCZ001>014-019-270815-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
Caldwell Mountains-Greater Caldwell-Burke Mountains-Greater Burke-
McDowell Mountains-Eastern McDowell-Rutherford Mountains-
Greater Rutherford-Polk Mountains-Eastern Polk-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Greater Greenville-Spartanburg-Cherokee-York-
Anderson-Abbeville-Laurens-Union SC-Chester-Greenwood-
405 AM EDT Mon Jul 26 2021

This Hazardous Weather Outlook is for northeast Georgia, piedmont
North Carolina, western North Carolina and upstate South Carolina.

.DAY ONE...Today and tonight.

A backdoor cold front will allow for shower and thunderstorm
development this afternoon into this evening. The main hazards are
cloud- to-ground lighting and heavy downpours. Any areas that
repeatedly see heavy downpours could experience excessive rainfall
leading to the potential for isolated flooding or flash flooding.
Isolated strong to severe thunderstorms cannot be ruled out. The main
potential impact from any strong to severe storm would be isolated
damaging wind gusts.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
620 PM EDT Mon Jul 26 2021

GAZ028-SCZ010-262245-
Hart GA-Anderson SC-
620 PM EDT Mon Jul 26 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN HART AND CENTRAL
ANDERSON COUNTIES UNTIL 645 PM EDT...

At 620 PM EDT, Doppler radar was tracking a strong thunderstorm 9
miles southwest of Anderson, or near Lake Hartwell, moving southeast
at 15 mph.

Locations to be impacted include...
Anderson, Homeland Park, Starr, Anderson Airport, Lake Hartwell, Reed
Creek, Northlake, Broadway Lake and Sadlers Creek State Park.

Wind gusts up to 40 mph will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

Torrential rainfall may flood areas with poor drainage, such as
ditches and underpasses. Avoid these areas and do not cross flooded
roads. Water levels of small streams may also rise rapidly. Seek
higher ground if threatened by flood waters.

&&

LAT...LON 3446 8292 3459 8273 3444 8254 3428 8280
TIME...MOT...LOC 2220Z 322DEG 11KT 3446 8279

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
645 PM EDT Mon Jul 26 2021

GAZ028-029-SCZ010-262315-
Elbert GA-Hart GA-Anderson SC-
645 PM EDT Mon Jul 26 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTH CENTRAL ELBERT...HART AND
SOUTHWESTERN ANDERSON COUNTIES UNTIL 715 PM EDT...

At 645 PM EDT, Doppler radar was tracking a strong thunderstorm near
Hartwell, moving southeast at 15 mph.

Locations to be impacted include...
Hartwell, Reed Creek, Bowersville, Lake Hartwell, Dewy Rose, Rock
Branch, Nuberg and Sadlers Creek State Park.

Wind gusts up to 40 mph will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

Torrential rainfall may flood areas with poor drainage, such as
ditches and underpasses. Avoid these areas and do not cross flooded
roads. Water levels of small streams may also rise rapidly. Seek
higher ground if threatened by flood waters.

&&

LAT...LON 3436 8308 3448 8291 3430 8267 3413 8293
TIME...MOT...LOC 2245Z 322DEG 11KT 3437 8294

ARK

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