Severe Thunderstorm Warning 47, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
253 PM EDT Sat Jun 12 2021

.SYNOPSIS...
A backdoor cold front moves into the area this evening, interacting
with abundant moisture to produce scattered to widespread showers
and thunderstorms.  The front will settle to the south of our area
for Sunday, reducing shower and thunderstorm chances significantly
as another cold front approaches the mountains.  Another round
of widely scattered showers and storms is expected on Monday,
but behind the next front, dry and seasonable air will dominate
our weather through much of next week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 200 pm: Latest water vapor imagery indicates weak upper trough
centered over the region this afternoon. This has aided in
development of scattered to numerous showers and storms within broad
low level convergence axis over the heart of the CWA. The latest SPC
Mesoanalysis depicts a moderately unstable air mass characterized by
sbCAPE of around 2000 J/kg while conditions remain anomalously moist
with 1.7 to < 2 inch PWATs analyzed across much of the forecast
area. As such, heavy/locally excessive rainfall will remain the
primary concern, especially in association with training or
backbuilding cells. A couple of isolated pulse severe cells remain
possible, while 0-3km shear of around 15 kts may be just enough to
allow for some small degree of upscale growth/clustering, which
would pose a bit of a higher risk of isolated downbursts. Coverage
will again steadily diminish through the evening, with little
expected after midnight...when the upper trough axis is forecast to
be south of the forecast area. Min temps are expected to be a couple
of degrees above climo.

Quite a change in the weather is expected for Sunday, as much drier
deep layer air filters into the area in the wake of the trough.
While surface dewpoints will remain seasonably high, forecast
soundings from the Piedmont depict an environment that is capped
and/or features high-LFCs. Conditions should be more favorable over
the mountains, where SCT activity is forecast to develop during
mid/late afternoon. However, PoPs drop off to slight chance-at-best
across the foothills and Piedmont. Temps are forecast to be right
around normal.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 300 PM EDT Saturday: While we cannot rule out a few isolated
showers over the mountains Sunday evening, overnight Sunday
into Monday should be quiet as a cold front approaches from the
northwest.  As the front moves through the area Monday afternoon,
guidance is anticipating a brief surge of moisture and instability
during peak heating which should trigger isolated to scattered
showers and thunderstorms as the front drops SE.  The coverage and
intensity of any activity will largely be dependent on timing,
as the guidance is not in agreement about where across our area
the front will be located Monday afternoon.  Generally speaking,
areas west of the Blue Ridge Escarpment should be mostly dry and
the focus will be from the escarpment east and south.

Despite a wedge of 1.5-1.75" PWs in advance of the front for
Monday and the potential for some backbuilding cell development,
neither the higher resolution NAM nor the GFS or ECMWF are
particularly bullish about heavy rain coverage.  The most likely
areas to see efficient rainfall will be underneath the favored
initiation areas of the southern Escarpment and perhaps portions
of the SC Upstate and southern NC Piedmont where residence time
within the more unstable and moist airmass will be greatest.
In addition, bulk shear values <20kts suggest the threat for
organized strong to severe storms is very low despite SBCAPE values
possibly reaching 1500-2000 J/kg ahead of the front.  However,
dry mid-level air forecasts suggest that a few strong downbursts
cannot be ruled out.  The lack of coverage in the guidance can
at least be partially attributed to a relative lack of mid-level
forcing as the dominant mid-level trough is displaced north over
the Great Lakes, in addition to the timing issues mentioned above.
However, if low-level convergence, instability, and moisture flux
forecasts persist, it wouldn't be surprising to see an uptick in
PoPs as we approach Monday, especially if FroPa slows down.

Behind the front Monday night into Tuesday, quieter and drier
conditions will dominate the rest of the short term period as high
pressure builds into the Ohio Valley and a continental airmass
advects into the region.  Due to the proximity of the front over
the coast, isolated showers cannot be ruled out along and east
of I-77 Tuesday afternoon.  Unfortunately, we will not be tapping
into any cooler air behind the front.  High temperatures both on
Monday and Tuesday will persist about 2-5 degrees above normal.
The biggest improvement will be in the humidity, as dewpoints drop
from the upper 60s into the lower 60s east of the mountains from
Monday to Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 300 PM Saturday: The general upper-level pattern through the
extended will be dominated by troughiness over the East Coast as
an expansive heat ridge dominates the western CONUS.  Therefore,
several shortwaves will rotate around the larger-scale trough
to keep our area in a generally northwest flow regime through the
work week.  Despite associated areas of strong vorticity, there will
be very little moisture ahead of these shortwaves and most of our
area will remain dry.  The best chances for light showers will be
over the TN border counties on Wednesday.  A strong shortwave will
propagate SE into the Carolinas and the predominate northwest flow
will induce modest upslope forcing over E TN.  There may be just
enough moisture to induce isolated showers into the NW Piedmont
Wednesday afternoon as the shortwave passes by.  The pattern will
support very pleasant humidity values through most of the work week
and seasonable temperatures, with an uptick in humidity heading into
Friday and the weekend as moist southerly flow returns to the area.

The next chance of any meaningful rainfall will be next weekend
as another weak cold front approaches the area.  At this time it
appears the location of the eastern CONUS trough axis and the
attendant surface front will suppress deeper tropical moisture
south of our area beyond the extended.  Of course, we will have to
monitor the timing and placement of the trough axis as we approach
next weekend because a slower arrival would allow deeper tropical
moisture to impact our area while a faster passage would suppress
any tropical moisture further south.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: Convection has been expanding in coverage and
intensity quickly over the past hour, and it looks like a virtual
certainty that all TAF sites will see (or will again see) at least
an hour or so of TS activity into the evening hours. As such,
VCSH/VCTS and tempos for TSRA are included through 22Z. These may
eventually need to be extended for an hour or two, especially at
the upstate SC terminals. Moist environmental conditions warrant
including IFR visby in the tempo along with MVFR cigs and gusty
winds. Coverage should steadily diminish through the evening, and
not much convection is expected past midnight. Moist conditions
north of a weal back door cold front is expected to result in
expanding/lowering cigs across much of the area late tonight into
early Sunday, with IFR/low MVFR cigs becoming likely. Less mid/upper
level cloud cover should also allow for more in the way of valley
fog/low stratus in the mountain valleys, and LIFR conditions are
carried at KAVL by around daybreak. Winds are expected to remain/
return to NE at 5-10 kts and continue there through at least Sunday
morning. Although the low levels will remain moist tomorrow,
significant drying is expected in the mid/upper levels, and
convection is expected to be much more suppressed while getting a
later start. As such, there are no Prob30s for TSRA during the
outlook period.

Outlook: A brief uptick in showers and thunderstorms will return
with a passing cold front late Monday into early Tuesday. Drier air
behind the front is expected to result in a convection-free period
from Tue afternoon through the end of the week. The potential for
overnight and morning fog and low cigs should become increasingly
confined to the mtn valleys next week.

Confidence Table...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       High  97%     High  81%     High  90%     High  94%
KGSP       High 100%     High  96%     High  87%     High  96%
KAVL       High  99%     High  99%     Med   71%     High  93%
KHKY       High  95%     Med   78%     High  83%     High  90%
KGMU       High 100%     High  97%     High  81%     High  93%
KAND       High 100%     High 100%     High  84%     High  90%

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...JMP
NEAR TERM...JDL
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
433 AM EDT Sat Jun 12 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-130845-
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-
433 AM EDT Sat Jun 12 2021

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

.DAY ONE...Today and tonight.

Showers and thunderstorms will develop across the region today,
primarily this afternoon and early this evening. The thunderstorms
will move slowly and produce torrential rainfall in affected
locations. Any areas experiencing repeated thunderstorms in a short
period of time may see flooding of low-lying areas and stream beds.
Any of the thunderstorms will have the potential to produce
dangerous cloud to ground lightning and gusty winds. A few of the
thunderstorms may produce damaging wind gusts.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

MPR

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
152 PM EDT Sat Jun 12 2021

SCZ011-019-121830-
Abbeville SC-Greenwood SC-
152 PM EDT Sat Jun 12 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT SOUTHERN ABBEVILLE AND
SOUTHWESTERN GREENWOOD COUNTIES UNTIL 230 PM EDT...

At 151 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 8 miles south of
Greenwood to 7 miles south of Abbeville to 16 miles northeast of
Elberton, and moving south at 10 mph.

Locations to be impacted include...
Calhoun Falls, Troy, Lowndesville, Lake Russell, Promised Land,
Bradley, Richard B Russell Dam and Callison.

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.

&&

LAT...LON 3402 8225 3397 8230 3406 8233 3406 8244
      3408 8248 3407 8253 3402 8259 3407 8264
      3410 8265 3427 8264 3414 8245 3414 8214
      3399 8213 3397 8218
TIME...MOT...LOC 1751Z 341DEG 9KT 3408 8221 3408 8243 3421 8260

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
157 PM EDT Sat Jun 12 2021

SCZ007-009-012>014-121845-
York SC-Laurens SC-Union SC-Chester SC-Spartanburg SC-
157 PM EDT Sat Jun 12 2021

...THUNDERSTORMS WITH TORRENTIAL RAINFALL WILL IMPACT EAST CENTRAL
LAURENS...WESTERN CHESTER...SOUTHWESTERN YORK...SOUTH CENTRAL
SPARTANBURG AND CENTRAL UNION COUNTIES UNTIL 245 PM EDT...

At 156 PM EDT, Doppler radar indicated thunderstorms with torrential
rainfall along a line extending from near York to 12 miles northeast
of Laurens, and moving south at 15 mph.

Locations to be impacted include...
Union, Chester, York, Monarch Mill, Buffalo, Lockhart, Carlisle,
Mcconnells, Lowrys and Chester State Park.

Wind gusts up to 40 mph 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.

&&

LAT...LON 3444 8180 3465 8191 3478 8153 3504 8116
      3480 8102 3457 8139 3457 8142 3456 8142
      3450 8159 3453 8162 3453 8164 3448 8169
TIME...MOT...LOC 1756Z 339DEG 9KT 3499 8119 3463 8188

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
215 PM EDT Sat Jun 12 2021

SCZ007-013-121845-
Union SC-Spartanburg SC-
215 PM EDT Sat Jun 12 2021

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN SPARTANBURG AND
WEST CENTRAL UNION COUNTIES UNTIL 245 PM EDT...

At 214 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles south of Spartanburg, or 4 miles southeast of Moore, moving
south at 20 mph.

Locations to be impacted include...
Moore, Croft State Park, Pauline and Enoree.

Wind gusts up to 40 mph, half inch 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.

&&

LAT...LON 3465 8195 3483 8203 3488 8188 3472 8172
      3464 8194
TIME...MOT...LOC 1814Z 338DEG 26KT 3479 8193

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
355 PM EDT Sat Jun 12 2021

NCZ069>071-SCZ007>009-013-014-122045-
Gaston NC-Lincoln NC-Mecklenburg NC-York SC-Cherokee SC-Union SC-
Chester SC-Spartanburg SC-
355 PM EDT Sat Jun 12 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT SOUTHEASTERN LINCOLN...
SOUTHWESTERN MECKLENBURG...EASTERN GASTON...NORTHWESTERN CHESTER...
YORK...SOUTHEASTERN SPARTANBURG...SOUTHERN CHEROKEE AND NORTHERN
UNION COUNTIES UNTIL 445 PM EDT...

At 354 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 10 miles west of
Huntersville to 5 miles west of York to 4 miles northeast of
Spartanburg, and moving south at 25 mph.

Locations to be impacted include...
Spartanburg, Union, York, Gastonia, Rock Hill, Southwest Charlotte,
Mt Holly, Belmont, Tega Cay and Clover.

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.

&&

LAT...LON 3515 8088 3466 8130 3467 8199 3502 8199
      3502 8133 3548 8098
TIME...MOT...LOC 1954Z 357DEG 33KT 3541 8103 3500 8133 3500 8189

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
419 PM EDT Sat Jun 12 2021

SCZ004-005-010-122045-
Greater Pickens SC-Greater Oconee SC-Anderson SC-
419 PM EDT Sat Jun 12 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN ANDERSON...
SOUTHWESTERN PICKENS AND EAST CENTRAL OCONEE COUNTIES UNTIL 445 PM
EDT...

At 419 PM EDT, Doppler radar was tracking a strong thunderstorm near
Clemson, or near Pendleton, moving south at 20 mph.

Locations to be impacted include...
Clemson, Anderson, Central, Northlake, Pendleton, Norris, Lake
Hartwell, Anderson Airport, Sandy Springs and Townville.

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.

&&

LAT...LON 3475 8287 3477 8275 3450 8265 3449 8290
TIME...MOT...LOC 2019Z 357DEG 17KT 3464 8280

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
448 PM EDT Sat Jun 12 2021

GAZ028-SCZ010-122115-
Hart GA-Anderson SC-
448 PM EDT Sat Jun 12 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN HART AND WEST
CENTRAL ANDERSON COUNTIES UNTIL 515 PM EDT...

At 448 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles south of Clemson, or 4 miles southwest of Pendleton, moving
south at 25 mph.

Locations to be impacted include...
Pendleton, Reed Creek, Anderson Airport, Lake Hartwell, Northlake,
Townville, Sandy Springs and Sadlers Creek State Park.

Wind gusts up to 45 mph, nickel 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.

&&

LAT...LON 3442 8292 3457 8290 3466 8280 3466 8272
      3443 8269
TIME...MOT...LOC 2048Z 000DEG 21KT 3459 8282

KRENTZ