Severe Thunderstorm Warning 244, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
543 PM EDT Sat Jul 21 2018

.SYNOPSIS...
A broad upper low will settle across the Deep South through early
next week. This low will remain nearly stationary through midweek
and support moist unsettled weather across the region.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 530 PM EDT Saturday: Atmosphere continues to destabilize this
afternoon with a finger of CAPE >3000J/kg stretching from GA up to
the Blue Ridge. Still impressive DCAPE values across the Upstate and
stretching into NC. As of update time, SPC just issued a SVR Tstorm
watch for a big chunk of the area (all our SC and GA counties and a
few NC). Have updated pops for current radar trends and increased
with a trend east over the next few hours. Temperatures still look
good at this time.

Otherwise, water vapor imagery and RAP heights placed the 500 mb
closed low center near the IL/IN/MI border this afternoon, with
drier mid-level air wrapping around the associated trough and across
the western Carolinas and northeast Georgia. Very good insolation
developed late this morning into this afternoon behind the departing
daybreak rain areas, and LAPS surface based CAPE values have
gradually returned to 1500 to 2500 J/kg across northeast GA and the
western Upstate. RAP and NAM profiles are very unstable this
afternoon, especially across our southern parts, where sbCAPE values
reach some 3000 to 4000 J/kg. The convection-allowing models have
not been terribly consistent on placement or timing, but the general
consensus is that enough triggering will take place as vorticity
lobes round the trough axis to generate scattered to numerous
thunderstorms later this afternoon and this evening. These
thunderstorms will grow in an enviroment with 7+ deg C/km mid-level
lapse rates and approximately 30 to 35 kt of sfc-6 km bulk shear.
This should be sufficient to warrant a Slight risk of severe
thunderstorms across our southern half, with a Marginal risk across
the northern part. Rotating updrafts will support mainly a damaging
wind and large hail threat. The consensus HRRR/NAMnest solution has
mountain triggering overcoming a weak cap circa 19Z, with activity
then developing and spreading quickly east of the mountains through
evening, moving east of the I-77 corridor by midnight. PoPs will
generally follow this trend.

Otherwise, the vertically stacked low pressure system will slowly
pivot southward toward the Ohio River Valley later tonight through
Sunday. Q-vector divergence will continue east of the deepening
trough axis mainly along the I-40 corridor. Reasonably steep 6 to
6.5 deg C/km lapse rates continue on Sunday east of the upper
trough. This will warrant at scattered south to numerous north
coverage again, with mainly a diurnal focus Sunday afternoon.
Temperatures should be at least a category below climo Sunday
afternoon.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 130 PM EDT Saturday: Active weather is likely to continue for
the period from Sunday night through Tuesday. The synoptic scale
feature of interest acrs the eastern CONUS will be the slowly
filling and southward sinking closed upper low.  With the mean
southerly flow atop the region deepening on Monday, expect an influx
of higher PWAT values leading to numerous if not widespread
diurnally enhanced deep convection with a heavy rain possibility
especially from the Blue Ridge to the piedmont. Widespread clouds
and showers should aid in max temperatures topping out around 5 deg
F below climo. It does not look like the sensible wx will change
very much through Tuesday, lingering rich PWAT values and a broad
SSEly flow feeding moisture into the Southern Appalachians. Expect
another day of deep convection becoming numerous to widespread with
the ongoing chance of locally excessive rainfall.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 115 PM Saturday: A weakening ulvl trof will linger over the
region thru the first half of the ext range before becoming sheared
out Fri into Sat. This synoptic scenario is well agreed upon by the
op models with the GFS holding onto a pocket of stronger vort energy
a little longer into Fri. At the sfc...broad low pressure will allow
for continued e/ly Atl moist flux early Wed before the deep layered
flow calms and becomes sw/ly in the lower levels Wed night thru the
period. This will lower any flooding potential as sustained mech lift
is reduced...however PWAT values will remain quite high allowing for
high rainfall rates associated with afternoon pulse convec. With
high cloud cover and decent coverage of precip...max temps will
remain a cat or so below normal with normal levels likely returning
Fri/Sat. Mins will remain a little abv normal each morning.

&&

.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: Convection is off to a very slow start this
afternoon as a weak cap remains in place in the profiles. Triggering
should force convection earliest over the mountains around 19Z, with
coverage growing eastward through the late afternoon and evening
hours. All locations will see TEMPO TSRA at some point in the 20Z to
22Z period, with gusts added given the potential for strong
updrafts/downdrafts. Considering the near surface moisture, heating
is producing some MVFR level clouds this afternoon in southwest
parts, but these should rise quickly to VFR levels with any
additional restrictions confined to thunderstorms. Expect mainly
southwest winds, with low end gusts at times, and a shift to NW flow
at KAVL late. Showers should return from KAVL to KHKY a bit earlier
on Sunday given the trough axis setting up to the west.

Outlook: An active/wet period is expected to continue from late
Sunday through the middle part of next week as a slow-moving storm
system impacts much of the East. Numerous showers and thunderstorms
are expected during this period. While there will likely be an
afternoon/evening peak in coverage on most days, higher-than-normal
chances will also exist during the overnight and morning hours.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High 100%     High 100%     High  89%     High 100%
KGSP       High 100%     High  98%     High  94%     High 100%
KAVL       High 100%     High 100%     Low   49%     High 100%
KHKY       High 100%     High 100%     High 100%     High  98%
KGMU       High 100%     High 100%     High  96%     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...SBK
NEAR TERM...HG/TDP
SHORT TERM...CSH
LONG TERM...SBK
AVIATION...HG

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
550 PM EDT Sat Jul 21 2018

GAZ010-017-018-026-028-029-NCZ068>070-507>510-SCZ001>014-019-222200-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Cleveland-Lincoln-
Gaston-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-Chester-Greenwood-
550 PM EDT Sat Jul 21 2018

...SEVERE THUNDERSTORM WATCH 300 IN EFFECT UNTIL 2 AM EDT SUNDAY...

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

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

Thunderstorms will continue to develop and expand in coverage across
the region into this evening. Some of these storms may become
severe. The most likely hazards will be damaging winds, large hail,
frequent lightning, and minor flooding from heavy rainfall. An
isolated tornado will also be possible, mainly east of the Blue
Ridge.

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

..Sunday...No hazardous weather is expected at this time.
..Monday...Heavy rain possible. A persistent moist southeasterly
flow will increase the risk for heavy rainfall across the area
starting late Monday and continuing through Wednesday.
..Tuesday...Heavy rain possible.
..Wednesday...Heavy rain possible.
..Thursday...No hazardous weather is expected at this time.
..Friday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Skywarn spotters are requested to forward any reports of large hail,
damaging winds, tornadoes, or flash flooding to our office.

NCZ033-035>037-048>053-056>059-062>065-071-072-082-501>506-222200-
Avery-Alexander-Iredell-Davie-Madison-Yancey-Mitchell-Swain-Haywood-
Buncombe-Catawba-Rowan-Graham-Northern Jackson-Macon-
Southern Jackson-Transylvania-Henderson-Mecklenburg-Cabarrus-Union-
Caldwell Mountains-Greater Caldwell-Burke Mountains-Greater Burke-
McDowell Mountains-Eastern McDowell-
550 PM EDT Sat Jul 21 2018

This Hazardous Weather Outlook is for piedmont North Carolina and
western North Carolina.

.DAY ONE...Tonight.

Thunderstorms will continue to develop and expand in coverage across
the region into this evening. Some of these storms may become
severe. The most likely hazards will be damaging winds, large hail,
frequent lightning, and minor flooding from heavy rainfall. An
isolated tornado will also be possible, mainly east of the Blue
Ridge.

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

..Sunday...No hazardous weather is expected at this time.
..Monday...Heavy rain possible. A persistent moist southeasterly
flow will increase the risk for heavy rainfall across the area
starting late Monday and continuing through Wednesday.
..Tuesday...Heavy rain possible.
..Wednesday...Heavy rain possible.
..Thursday...No hazardous weather is expected at this time.
..Friday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Skywarn spotters are requested to forward any reports of large hail,
damaging winds, tornadoes, or flash flooding to our office.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
609 PM EDT SAT JUL 21 2018

GAZ018-026-SCZ001-004-212245-
Franklin GA-Stephens GA-Greater Oconee SC-Oconee Mountains SC-
609 PM EDT SAT JUL 21 2018

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN FRANKLIN...CENTRAL
STEPHENS AND SOUTHWESTERN OCONEE COUNTIES UNTIL 645 PM EDT...

At 609 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles northeast of Toccoa, moving east at 20 mph.

Locations to be impacted include...
Toccoa, Westminster, Gumlog, Tugaloo State Park and Oakway.

Wind gusts up to 40 mph and pea size hail 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.

&&

A Severe Thunderstorm Watch remains in effect until 200 AM EDT for
northeastern Georgia...and Upstate South Carolina.

LAT...LON 3461 8337 3475 8331 3468 8298 3446 8308
TIME...MOT...LOC 2209Z 291DEG 16KT 3464 8323

08

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
612 PM EDT SAT JUL 21 2018

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

0606 PM     HAIL             1 ENE MORGANTON         35.75N 81.68W
07/21/2018  E1.00 INCH       BURKE              NC   TRAINED SPOTTER

            TRAINED SPOTTER REPORTED QUARTER SIZE HAIL IN
            MORGANTON.

&&

LEC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
619 PM EDT SAT JUL 21 2018

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

0610 PM     HAIL             DREXEL                  35.75N 81.61W
07/21/2018  E1.00 INCH       BURKE              NC   BROADCAST MEDIA

            QUARTER (1.00 IN) SIZE HAIL REPORTED ON ET CAMP RD
            NEAR DREXEL

&&

LEC

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
633 PM EDT SAT JUL 21 2018

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

0615 PM     TSTM WND DMG     1 W VALDESE             35.75N 81.57W
07/21/2018                   BURKE              NC   BROADCAST MEDIA

            TREES AND POWERLINES DOWN ON CHURCH ST. NW AND DIXIE
            AVE NORTHWEST. TIME ESTIMATED FORM RADAR.

&&

LEC

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
637 PM EDT SAT JUL 21 2018

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

0637 PM     HEAVY RAIN       4 SSW BAT CAVE          35.39N 82.31W
07/21/2018  M2.50 INCH       HENDERSON          NC   MESONET

&&