Severe Thunderstorm Warning 221, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
505 PM EDT Wed Jul 19 2017

.SYNOPSIS...
An upper level ridge will build over our region from the west
through the end of the week. This pattern will give the Carolinas
and northeast Georgia some of the hottest weather so far this season
along with showers and storms mainly restricted to the mountains. A
broad upper level trough develops this weekend and into next week
which lowers temperatures.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 500 PM EDT Wednesday: Grids look good for the late afternoon
update, with pop trends maybe a little high, but with dCAPEs
continuing to hover near 1000J/kg for the area no plans to lower
just yet.

Otherwise, a mid/upper level low pressure center continues to spin
over the eastern NC piedmont and coastal plain this afternoon. This
feature will continue to drift southeast over the coastal waters of
the Carolinas before retrograding west across coastal Georgia and
northern Florida through Thursday. West of this low, the convection-
allowing models have very sparse thunderstorm coverage across the
region this afternoon and evening with limited triggering. However,
isolated to scattered thunderstorm coverage remains possible in weak
triggering along the high terrain and also in the better instability
near pre-existing boundaries over the lower piedmont. With sbCAPE
values running 2000 to 3000 J/kg in the southeast half of the area,
and with decent surface to mid level theta e lapses still in place,
a few storms could be strong to severe through early evening. Expect
profiles to stabilize quickly with the loss of heating through late
evening. Another round of mainly mountain valley fog and low clouds
are expected overnight.

Even less convective coverage is expected on Thursday as mid and
upper level ridging noses more strongly over the region and produces
warmer temperatures aloft. Steering flow will remain very light up
the column through the period, so locally heavy rainfall will also
be possible under any showers/thunderstorms that manage to develop.
With 850 mb temps rising another degree C or so through Thursday
afternoon, plenty of mid 90s max temperatures are expected.
Fortunately, dewpoint mixing should cap off heat index values at
around 100 degrees or less.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 200 PM Wed: As the upper ridge builds east, heights continue to
rise through Friday, but begin to fall slightly on Saturday as the
next trough digs over the northern Plains. Return flow around the
Bermuda High will continue unabated, as will hot and humid
conditions. Heat indices, per this cycle of guidance, are likely to
exceed 100 but not 105. Nonetheless that may be enough to warrant
caution in sensitive groups and a Heat Advisory could be warranted
at some point.

Both afternoons, the midlevel temps resulting from the warm flow are
too warm to permit much, if any, Piedmont convection. However, the
models feature some development over the high terrain both days,
particularly Saturday. Weak wind profiles imply pulse storms.
Despite the humid conditions at the surface, the mid to upper levels
are quite dry and damaging winds cannot be ruled out with the
stronger cells either day.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 100 PM Wed: Heights begin to fall over the Eastern states
Saturday night as a clipper shortwave moves into the upper
Mississippi Valley region. This wave will move along an existing
stationary boundary, initiate cyclogenesis over the eastern Great
Lakes, and push a cold front gradually southeastward. Slightly higher
PoPs appear warranted Sunday afternoon with the suppression of the
ridge. The approach and arrival of the front then will elevate precip
chances Monday and Tuesday across the forecast area. The front is
should initiate a cooling trend and drop temps and dewpoints back to
near normal late in the period. PWAT values most likely will be 1 or
more standard deviations above normal along and ahead of the front,
but our upper level flow does not increase much due to the better
upper support remaining to our north. These findings suggest we will
trade our weekend pulse storms and associated wind concerns for the
threat of slow-moving storms producing heavy rainfall early next
week.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: No changes to the KCLT TAF for the 21z
AMD. Very isolated coverage in the weak triggering should keep most
thunderstorms away from the TAF sites through early evening. Thus,
expect mainly FEW to SCT VFR cumulus clouds with light winds. Mixing
should keep winds north of west at KAVL, KHKY, and KCLT, with some
adjustment to WSW in parts of the Upstate. A trend toward light
southerly is expected overnight, with winds returning light WSW to
WNW for Thursday. Expect fog and low clouds once again mainly in the
mountain river valleys around daybreak. Thunderstorm coverage will
be even less on Thursday with warmer temperatures aloft.

Outlook: Drier air will likely continue to limit convective coverage
and the extent of low clouds and fog through Friday. Chances for
diurnal convection begin a steady increase on Saturday, with this
trend continuing into early next week ahead of an approaching cold
front on Monday.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  94%     Low   27%     High 100%
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 and ensemble forecasts
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...HG/TDP
SHORT TERM...Wimberley
LONG TERM...Wimberley
AVIATION...HG/TDP

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
629 AM EDT Wed Jul 19 2017

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-201030-
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-
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-Chester-Greenwood-
629 AM EDT Wed Jul 19 2017

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

.DAY ONE...Today and Tonight.

Isolated to scattered thunderstorms are expected to develop again
across the area this afternoon and evening. The main threats will be
from cloud to ground lightning and locally heavy rainfall. However,
a few storms could become severe, with damaging winds being the primary
threat.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

..Thursday...No hazardous weather is expected at this time.
..Friday...No hazardous weather is expected at this time.
..Saturday...No hazardous weather is expected at this time.
..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

JPT

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
405 PM EDT WED JUL 19 2017

NCZ036-056-192030-
Iredell NC-Catawba NC-
405 PM EDT WED JUL 19 2017

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN CATAWBA AND WEST
CENTRAL IREDELL COUNTIES UNTIL 430 PM EDT...

At 405 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles southwest of Statesville, or 4 miles east of Catawba, moving
south at 10 mph.

Locations to be impacted include...
Catawba, Lake Norman State Park, Troutman, Lake Norman, Bandys and
Sherrills Ford.

Wind gusts up to 40 mph and pea size hail will be possible in these
areas.

LAT...LON 3576 8109 3579 8094 3565 8086 3561 8108
TIME...MOT...LOC 2005Z 351DEG 7KT 3573 8100

CDG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
509 PM EDT WED JUL 19 2017

SCZ001-192145-
Oconee Mountains SC-
509 PM EDT WED JUL 19 2017

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN OCONEE COUNTY UNTIL
545 PM EDT...

At 508 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles west of Walhalla, or 7 miles east of Tallulah Gorge State Park,
moving south at 15 mph.

Locations to be impacted include...
Long Creek.

Wind gusts up to 50 mph and dime size hail will be possible in these
areas.

LAT...LON 3476 8332 3479 8333 3481 8330 3482 8330
      3478 8310 3463 8312 3460 8316 3461 8323
      3464 8326 3464 8327 3468 8332 3468 8334
      3469 8334 3470 8335 3473 8335
TIME...MOT...LOC 2108Z 013DEG 12KT 3473 8323

CDG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
550 PM EDT WED JUL 19 2017

NCZ070-071-192215-
Gaston NC-Mecklenburg NC-
550 PM EDT WED JUL 19 2017

...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL MECKLENBURG AND
SOUTHEASTERN GASTON COUNTIES UNTIL 615 PM EDT...

At 550 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles northwest of Uptown Charlotte, or near Paw Creek, moving south
at 10 mph.

Locations to be impacted include...
Central Charlotte, Northwest Charlotte, Charlotte Douglas Airport,
Paw Creek, Southwest Charlotte, Belmont and Mt Holly.

Wind gusts up to 40 mph and pea size hail will be possible in these
areas.

LAT...LON 3514 8085 3516 8106 3527 8102 3531 8100
      3530 8089
TIME...MOT...LOC 2150Z 008DEG 7KT 3527 8096

CDG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
616 PM EDT WED JUL 19 2017

SCZ009-014-192245-
York SC-Chester SC-
616 PM EDT WED JUL 19 2017

...A STRONG THUNDERSTORM WILL IMPACT NORTH CENTRAL CHESTER AND SOUTH
CENTRAL YORK COUNTIES UNTIL 645 PM EDT...

At 616 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles southwest of Rock Hill, or 7 miles east of Mcconnells, moving
south at 20 mph.

Locations to be impacted include...
Chester and Richburg.

Wind gusts up to 45 mph and pea size hail will be possible in these
areas.

LAT...LON 3490 8112 3488 8103 3467 8102 3471 8126
TIME...MOT...LOC 2216Z 010DEG 20KT 3484 8110

CDG