Severe Thunderstorm Warning 297, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
520 PM EDT Thu Aug 9 2018

.SYNOPSIS...
A weak cold front approaching from the northwest today will stall
across the region Friday into the weekend. Seasonably warm
temperatures and scattered to numerous afternoon and evening showers
and thunderstorms will continue. An upper level disturbance will
move across the area on Monday leading to drier weather on Tuesday
and Wednesday.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 5pm EDT Thursday:  Some thunder this afternoon, primarily
moving southeast along a line from Jackson County NC  to Laurens
County SC.  Expectations are for these storms to remain active for
the next several hours while moving southeast.  Other storms are
expected to move in from the west over the next couple hours.  These
storms have been sub-severe in TN and GA thus far, and are expected
to weaken some as they cross the mountains and outrun upper forcing
support.  However, some thunder will persist over western parts of
the CWA through the evening, with CAMs showing rapid declines after
9pm.

Friday, a fairly vigorous vort max will drift from the Ozarks to TN
Valley, entering the southern Appalachians around 00z Sat. This
feature may enhance convective chances in the aftn and early evening
hours. CAMs that go out thru 00z Saturday all show fairly numerous
cells with some multi-cell structures, mainly across the NC zones.
Still looks only moderately unstable (CAPE 1000-2000 J/kg), but
shear increases to around 20-30 kts in the aftn. I have bumped up
PoPs into the likely range across most of the NC zones. Chc PoPs
will be carried south. Severe threat will be marginal, with winds
being the main threat. Highs will be near to slightly above normal,
mainly in the 80s to lower 90s.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 215 PM EDT Thursday: At the start of the short term period, a
very large upper ridge will be in place over the rockies, with a
trough over eastern Canada lifting northeast, and a midlevel
shortwave pushing across the southern Appalachians. Lingering
surface boundary stretched across the Piedmont will remain in place.
As the shortwave works its way across the mountain, lingering
convection from Friday afternoon should spill over into the early
part of the period and isolated showers may continue overnight
especially across NC zones. Of interest is that the little shortwave
looks like it might induce lee low development across the Piedmont
on the former boundary, which may linger across the area into
Saturday. This initial shortwave will damp and lift northeast toward
New England Friday night into Saturday as a secondary wave deepens
and stretches from the Great Lakes to a lingering weakness over the
Southern Plains. CAPEs look a little lower on Saturday afternoon and
so with the loss of more forcing the Piedmont should see slightly
lower (but still higher than diurnal) convection, but should see
more widespread thunderstorms across the mountains especially with
the upslope contribution into the southwest mountains from flow
around the weak lee low.

The Great Lakes trough deepens and cuts off over the Midwest as we
move through Saturday night and Sunday, and with the southwest flow
aloft over our area plus little impulses and a jetlet riding around
the base of the trough, there should again be plenty of upper
forcing for convection to fire area-wide, though focused mainly in
the mountains. As usual, the NAM is a little more bullish with CAPE
recovery in the afternoon whereas the GFS keeps generally <700J/kg
across the area (NAM over twice that), so some uncertainty about how
intense the storms might be, but as with the past few days and again
Saturday, with the upper flow, storms should continue to move to
help mitigate flash flooding concerns, though by this point the
increasingly saturated soils may be problematic with any convection.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 245 PM EDT Thursday: The Midwest upper low will slowly begin
to push east as we start the work week, with the trough axis passing
across our area Monday night into Tuesday morning. Expect a decrease
in convective activity from west to east on Monday, and should see a
relative lull in activity (there will still be convection, but
generally below the typical diurnal trend) Tuesday into Wednesday on
the upstream side of the trough as weak ridging tries to build back
in. Another shortwave will push toward the mid MS Valley by the end
of the period with a corresponding increase in pops. Expect fairly
seasonal temperatures through the period.

&&

.AVIATION /21Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Current trends on radar and vis sat imagery
are in line with expected convective evolution this aftn thru this
evening. Deeper convection is starting to fire across the NC
mountains, with a minimum across the piedmont. Within the WNW flow,
streamers are forming off the mountains in three enhanced cumulus
bands. One of them is setting up just north of KGSP, and pretty much
all the guidance agrees on TSRA forming in this area within the next
couple hours. So VCTS will be carried at KGSP/KGMU for the first few
hours of the TAF. VCTS will also be carried at KAVL and KAND.
Limited instability across the NC piedmont results in only an
isolated chc of a TSRA at KHKY and KCLT, so no mention will be
carried at those sites. Convection will wane after sunset, leaving
patchy mid clouds overnight. Fog and stratus should be mainly
confined to the mountain valleys. Will prevail an IFR cig at KAVL
late tonight.

On Friday, a return of greater convective coverage is expected,
especially across western NC sites. Will add a PROB30 for Friday
aftn at KCLT.

Outlook: Typical mid-summer conditions are fcst the next several
days. Diurnal, scattered thunderstorms will continue mainly in the
afternoons, with coverage increasing toward the weekend. Associated
morning restrictions will be possible each day, especially in
mountain valleys. A possible break in aftn convection is possible on
Tuesday, as some drier air works in from the west.

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  83%     High 100%
KAVL       High 100%     High 100%     Med   61%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High  94%     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...TDP
NEAR TERM...ARK/WJM
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...ARK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
354 AM EDT Thu Aug 9 2018

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-101100-
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-
354 AM EDT Thu Aug 9 2018

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

.DAY ONE...Today and tonight.

Isolated to scattered thunderstorms will develop around the region
this afternoon and evening. Thunderstorm coverage will be greatest
across the mountains. Any of the thunderstorms will have the
potential to produce cloud-to-ground lightning, gusty winds, and
locally heavy rainfall.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Thunderstorm coverage will be fairly high each afternoon and evening
from Friday through Monday. The main impacts will be cloud-to-
ground lightning, heavy rainfall, and gusty winds. Isolated flooding
will be possible each day as the rainfall totals accrue.

.SPOTTER INFORMATION STATEMENT...

None.

HG

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
256 PM EDT THU AUG 9 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0620 PM     TSTM WND DMG     7 WSW KANNAPOLIS        35.44N 80.74W
08/08/2018                   CABARRUS           NC   PUBLIC

            PUBLIC REPORTED A TREE DOWN AT THE INTERSECTION OF NC
            73/DAVIDSON HWY AND WELLINGTON CHASE DR. TIME
            ESTIMATED FROM RADAR.

&&

JMP

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
404 PM EDT THU AUG 9 2018

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0430 PM     TSTM WND DMG     2 NNE ROEBUCK           34.91N 81.95W
08/08/2018                   SPARTANBURG        SC   EMERGENCY MNGR

            EMERGENCY MNGR REPORTED NUMEROUS TREES AND POWERLINES
            DOWN IN ROEBUCK INCLUDING A DESTROYED CARPORT ALONG
            OLD AIRPORT RD.

&&

JMP

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
508 PM EDT THU AUG 9 2018

SCZ006-007-092200-
Spartanburg SC-Greater Greenville SC-
508 PM EDT THU AUG 9 2018

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT EAST
CENTRAL GREENVILLE AND WEST CENTRAL SPARTANBURG COUNTIES UNTIL 600 PM
EDT...

At 508 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 4 miles northeast of Greenville Downtown, or near
Taylors, moving southeast at 10 mph.

Locations to be impacted include...
Greenville Downtown, Greenville Eastside, West Greenville, Greer,
Mauldin, Taylors, Berea, Paris Mountain State Park, Lake Robinson and
GSP Airport.

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...

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.

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 3489 8250 3503 8235 3503 8234 3491 8211
      3471 8232
TIME...MOT...LOC 2108Z 310DEG 7KT 3492 8236

TDP