Severe Thunderstorm Warning 267, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
156 PM EDT Sat Jul 25 2020

.SYNOPSIS...
A stagnant pattern will result in continued typical mid summer
weather through early next week. A developing upper trough and
associated cold front are expected to enhance chances for mainly
afternoon and evening showers and thunderstorms during the latter
half of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1020 AM EDT Saturday: Other than a few pockets of mountain
valley fog/low stratus lingering over the most prone sites, most of
the cloud cover has burned off over the past few hours. The latest
CAM runs are still suggesting that convection will kick off over the
higher terrain by the early aftn.

Otherwise, the weakness in the 500 mb ridge remains in place today
across the Carolinas, altho it is less clear how much of an
influence this will have on our weather today. A weak remnant vort
center will drift over the region, but this one is weaker than the
wave that helped to organize the numerous/widespread showers and
storms of yesterday. Mid levels have warmed a bit as well, so sfc-
based CAPE may only top out in the 2000-3000 J/kg range in the
afternoon. This suggests less coverage compared to yesterday, and
the convection-allowing models tend to agree. The high elevations
have a lot going for them, so a likely precip prob will be retained
there, but we cut back to a chance across most of the area east of
the mtns with the expectation that convection will be more
scattered. The sfc-delta Theta-e is not as high and dCAPE potential
doesn't look quite as good as yesterday, so while a few pulse severe
storms are expected, the number should be no greater than yesterday.
Temps should be near normal which keeps the Heat Index in check.
Storms should be diurnally modulated again, so they will end by late
evening. Overnight min temps will be close to normal again.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 330 am Saturday: The persistent subtropical ridge will
maintain our typical late July pattern through much of the forecast
period. Summertime convection will be in store each afternoon
and evening with moderate instability and a low-level south to
southwesterly flow. Temperatures during the period should remain
at or slightly above climo for much of the cwa. A small change in
the overall pattern seems evident by model guidance during the
extreme far end of the short term. The change comes from the upper
low that sets up shop over Ontario and the Upper Great Lakes late
Monday into early Tuesday. With that, the subtropical ridge will
slowly fade out from the eastern CONUS as gradual height falls
and upper troughing begin to settle in. The ECMWF is slightly more
progressive than the NAM and GFS are with the eventual upper trough
that is expected to sag over the region. The extended will have more
information on the overall pattern change with some relief in site.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 300 AM EDT Saturday: The extended begins Tuesday morning with
an upper trough digging into the Great Lakes, and a shortwave
dancing along the tail end of the trough over the Ozarks. Attendant
surface front will be approaching the Appalachians, but with the
continued Piedmont trough in place at the surface. The height falls
associated with the longwave trough will split the subtropical ridge
in two as the trough takes up residence over the area. The period
will start with above-normal temperatures ahead of the front on
Tuesday, but with the frontal passage, temperatures are knocked down
a few degrees through the end of the period, ending up a couple of
degrees below normal. Convective trends will of course be mainly
diurnally-driven, but with a mountain focus given the proximity of
the front on Tuesday, and area-wide Wednesday. Later in the week,
depending on where the front stalls, we could see enhanced
convective trends or reduced; for now the global models are keeping
the front near or just south of the area so have continued the trend
of above-climo pops especially on Friday with a slug of upper
moisture moving across.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: Expect VFR conditions to prevail for most
sites thru the 18z taf period. As usual in late July, the main
exception will be restrictions that develop from any diurnally-driven
thunderstorm activity today/tonight and again tomorrow aftn/evening.
In addition, KAVL will likely see another round of IFR visby and
cigs overnight and into tomorrow morning, which should burn off by
13 or 14z. Otherwise, convective coverage should be less today than
yesterday, although chances are high enough that TEMPOs for TSRA were
included at all sites for the late aftn/early evening window. As
mentioned above, mountain valleys will likely see another round of
low stratus/fog overnight and tomorrow morning. Winds will become
light and vrb overnight, but otherwise favor a SLY to SWLY direction
thru the taf period.

Outlook: Diurnal showers and thunderstorms are expected each day
thru the extended fcst period. MVFR/IFR restrictions will be possible
each day in any thunderstorms and morning fog development, especially
in the mountain valleys. Otherwise, expect VFR conditions.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  95%     High  87%     High  91%
KHKY       High 100%     High 100%     High  87%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High 100%

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...CAC
NEAR TERM...JPT/PM
SHORT TERM...CAC
LONG TERM...TDP
AVIATION...JPT

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
454 AM EDT Sat Jul 25 2020

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-260900-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Iredell-Davie-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-
Rowan-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-
454 AM EDT Sat Jul 25 2020

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

.DAY ONE...Today and tonight.

Scattered afternoon to evening showers and thunderstorms are
expected today. Any storms that do develop will be capable of
producing cloud-to-ground lightning, gusty winds, and heavy rain.
Some storms have the potential to be strong to severe.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

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Special Weather Statement
National Weather Service Greenville-Spartanburg SC
211 PM EDT Sat Jul 25 2020

GAZ017-018-SCZ001-251845-
Stephens GA-Habersham GA-Oconee Mountains SC-
211 PM EDT Sat Jul 25 2020

...A STRONG THUNDERSTORM WILL IMPACT STEPHENS...EAST CENTRAL
HABERSHAM AND SOUTHWESTERN OCONEE COUNTIES UNTIL 245 PM EDT...

At 211 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles northeast of Toccoa, moving southwest at 10 mph.

Locations to be impacted include...
Toccoa, Avalon, Hollywood, Eastanolee and Boydville.

Wind gusts up to 40 mph, pea size hail and very heavy rainfall rates
up to 1 to 2 inches per hour 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 3465 8347 3476 8323 3464 8311 3460 8316
      3460 8317 3459 8317 3459 8316 3458 8316
      3457 8314 3448 8322 3447 8328
TIME...MOT...LOC 1811Z 048DEG 7KT 3465 8323

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
213 PM EDT Sat Jul 25 2020

NCZ501-502-504-251845-
Caldwell Mountains NC-Greater Burke NC-Greater Caldwell NC-
213 PM EDT Sat Jul 25 2020

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL CALDWELL AND CENTRAL
BURKE COUNTIES UNTIL 245 PM EDT...

At 213 PM EDT, Doppler radar was tracking a strong thunderstorm near
Lenoir, moving south at 5 mph.

Locations to be impacted include...
Lenoir, Sawmills, Gamewell, Hudson, Cajah's Mountain, Cedar Rock,
Lake Rhodhiss, Granite Falls, Collettsville and Patterson.

Wind gusts up to 40 mph, pea size hail and very heavy rainfall rates
up to 1 to 2 inches per hour 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 3601 8167 3599 8145 3577 8144 3582 8176
TIME...MOT...LOC 1813Z 009DEG 4KT 3593 8158

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
221 PM EDT Sat Jul 25 2020

NCZ505>508-251845-
Greater Rutherford NC-McDowell Mountains NC-Rutherford Mountains NC-
Eastern McDowell NC-
221 PM EDT Sat Jul 25 2020

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN MCDOWELL AND
NORTHWESTERN RUTHERFORD COUNTIES UNTIL 245 PM EDT...

At 221 PM EDT, Doppler radar was tracking a strong thunderstorm 9
miles south of Marion, moving south at 5 mph.

Locations to be impacted include...
Shingle Hollow, Green Hill, Sugar Hill, Thermal City, Glenwood, Fero,
Union Mills and Dysartsville.

Wind gusts up to 40 mph and very heavy rainfall rates up to 1 to 2
inches per hour 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 3561 8210 3562 8188 3540 8184 3541 8217
TIME...MOT...LOC 1821Z 003DEG 6KT 3555 8201

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
225 PM EDT Sat Jul 25 2020

NCZ064-065-SCZ003-251900-
Transylvania NC-Henderson NC-Greenville Mountains SC-
225 PM EDT Sat Jul 25 2020

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN TRANSYLVANIA...
SOUTH CENTRAL HENDERSON AND NORTHWESTERN GREENVILLE COUNTIES UNTIL
300 PM EDT...

At 225 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles south of Hendersonville, or 5 miles northeast of Jones Gap
State Park, moving southwest at 10 mph.

Locations to be impacted include...
Slater-Marietta, Pleasant Ridge State Park, Caesars Head State Park,
Jones Gap State Park, Dupont State Forest, North Saluda Reservoir,
Crab Creek, Cleveland, Cedar Mountain and Tuxedo.

Wind gusts up to 40 mph and very heavy rainfall rates up to 1 to 2
inches per hour 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 3518 8236 3500 8245 3498 8251 3500 8254
      3501 8254 3501 8256 3503 8258 3503 8259
      3504 8260 3506 8260 3506 8257 3507 8257
      3506 8266 3511 8275 3528 8255
TIME...MOT...LOC 1825Z 032DEG 8KT 3518 8251

HG