Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1030 AM EDT Fri Jul 16 2021

.SYNOPSIS...
Warm high pressure will dominate the southeast for another day. A
broad trough of low pressure, and an associated surface cold front,
will then approach from the northwest over the weekend. The trough
and front will slowly settle southeast of the area early next week,
with modest drying and cooling from the north through mid-week.
Temperatures will likely rebound later in the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1015 AM EDT Friday: Grids are looking in pretty good shape
for the most part. Already warming up pretty quickly out there so
temperature trends looking pretty good for an uncomfortable
afternoon. That said, 12z KGSO sounding had a pretty thick warm
layer just below 500mb, and CAMs aren't all that impressed. Reduced
pops somewhat for this afternoon as it seems that cap might be
difficult to overcome, with the typical exception of course of the
mountains where pops were relatively unchanged, also very little
change down toward the Lakelands. Will keep an eye on trends and if
it looks like cap might break after all might have to readjust. With
any convection that does occur, with high PW values, main concern
would be heavy downpours and isolated flash flooding concerns.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 200 am EDT Friday: An active weather weekend is shaping up for
the western Carolinas and northeast Georgia as a high precipitable
water airmass remains over the region between offshore high pressure
and a deepening trough to the west. The upstream 500 mb trough axis
will dig from the Great Lakes to the Ohio River Valley over the
weekend, while an associated surface cold front pushes steadily
toward the Appalachians. Fairly robust diurnal convection is
expected ahead of the approaching trough axis both Saturday and
Sunday afternoon and evening as surface-based CAPE values bubble up
above 2000 J/kg each day with peak heating. In addition, slightly
better shear profiles will develop atop the area over the weekend,
with pockets of 25+ kt sfc to 3 km bulk shear. Upper forcing with
the approaching trough will improve as an upper jetlet stretches out
along the Appalachians, bringing increasing upper-level divergence
to the region, especially on Sunday. Shower and thunderstorm
coverage should maximize in the likely to categorical range both
days, especially over northern and western sections where the
forcing will be best. Isolated severe thunderstorms will be possible
both days, but with slightly greater chances on Sunday afternoon.
The hydro risk will steadily build as well over the weekend, with
any training of thunderstorms possibly leading to isolated flash
flooding in the high PWAT airmass. The increasing clouds will likely
limit maximum temperatures to near climo on Saturday and a category
below on Sunday.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 245 am EDT Friday: The slowly-passing eastern U.S. trough axis
will likely cross the southern Appalachians on Monday, but with more
questionable progress off the coastline on Tuesday. The associated
surface cold front will likely settle slowly southeast across the
forecast area during this period as well. The gradual decrease in
moisture and forcing across the region will require continued above
climo PoPs early next week, especially for the southeast half of the
area. Temperatures should dip at least a category below climo given
the clouds and the onset of modest thickness falls with the fropa.

Deep-layer northwest flow should then be in place Wednesday through
Thursday. However, enough boundary layer moisture may linger over
the region for diurnal isolated to scattered convection to fire once
again. Improving insolation mid to late week should permit
temperatures to gradually rebound to climo values, with typical July
conditions likely by next Thursday.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: The rest of the morning should be mostly quiet
across the fcst area with light and vrb winds remaining calm at times
through the morning. Anticipate restrictions to continue at KAVL thru
roughly 14z with mountain valley fog/stratus already in place. Expect
the other taf sites to remain VFR this morning, but cannot rule out a
few brief restrictions over the next few hours. Otherwise, we can expect
another day of sct convection this aftn/evening, with overall coverage
not expected to exceed sct. As such, I maintained VCSH and PROB30s for
TSRA for the convective potential later today. Winds will remain SLY
to SWLY, except at KAVL, where a light NWLY wind this morning will
become SLY to SWLY this afternoon/evening.

Outlook: An unsettled pattern, with afternoon/evening showers and
thunderstorms and morning fog/low stratus, will persist thru the
weekend and into early next week. A front near the region may enhance
afternoon/evening convective coverage this weekend.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High  82%
KHKY       High 100%     High 100%     High 100%     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...HG
NEAR TERM...JPT/TDP
SHORT TERM...HG
LONG TERM...HG
AVIATION...JPT

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
418 AM EDT Fri Jul 16 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-170830-
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-
418 AM EDT Fri Jul 16 2021

This Hazardous Weather Outlook is for northeast Georgia, Piedmont
North Carolina, western North Carolina, and Upstate South Carolina.

.DAY ONE...Today and tonight.

Scattered showers and thunderstorms are expected to develop across
the western Carolinas and northeast Georgia this afternoon and
evening. Threats from these storms will include gusty winds, locally
heavy rainfall, and occasional cloud-to-ground lightning strikes.
The thunderstorms will diminish after midnight.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
143 PM EDT Fri Jul 16 2021

SCZ014-161815-
Chester SC-
143 PM EDT Fri Jul 16 2021

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT CENTRAL
CHESTER COUNTY UNTIL 215 PM EDT...

At 143 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 5 miles south of Chester, or near Chester State
Park, moving northeast at 30 mph.

Locations to be impacted include...
Chester, Richburg, Chester State Park, Cornwell and Blackstock.

In addition to intense lightning, wind gusts up to 40 mph, pea size
hail and very heavy rainfall rates up to 2 inches per hour will be
possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3456 8112 3457 8129 3462 8137 3482 8119
      3482 8116 3481 8106 3470 8093
TIME...MOT...LOC 1743Z 221DEG 26KT 3462 8123

KRENTZ