Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
948 PM EDT Fri Aug 13 2021

.SYNOPSIS...
A stormy pattern will persist over the area through the weekend,
with scattered if not numerous showers and thunderstorms developing
each afternoon. Temperatures will remain above normal through
Saturday. Cooler but still rainier weather will arrive Sunday with a
stalling cold front and possibly impacts from the remnants of
Tropical Storm Fred in the early to middle part of next week.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 945 pm EDT: Radar continues to depict isolated to scattered
thunderstorms developing mainly along the boundary left over by
earlier convection along the I-85 corridor from Charlotte to
Concord. Expect another hour or so of continued activity in this
area before the region finally stabilizes. Farther west across the
Upstate of SC, radar shows weak outflows working west and this
region still exhibits some late day 2000+ sbCAPE values in the
latest LAPS analysis. Will thus also feature isolated coverage there
through about midnight. Otherwise, the coverage should steadily
dwindle through the late evening and early overnight hours, although
small PoPs will be retained through the early morning hours near the
TN border as increasing moisture in advance of frontal zone
interacts with westerly low-level flow to initiate a few showers.
Patchy fog should be relegated mainly to the mountain river valleys
overnight, and any Piedmont locations that received heavy rain late
this evening.

Another day of moderate-to-strong instability is expected on
Saturday, while slight height falls are expected across the
Southeast as a major short wave trough passes across southeast
Canada and the northeast Conus. Meanwhile, the short term models
agree in depicting a lee/pre-frontal trough across the heart of the
CWA during the afternoon. Overall, forecast conditions are quite a
bit more favorable for deep convection Saturday afternoon, and
likely PoPs will be advertised across the mountains and portions of
the foothills, with 30-50% chances across the remainder of the
forecast area. There will also be an uptick in the severe weather
potential, owing largely to the higher overall coverage. Temps will
remain above normal through the period, with max heat indices
expected to range in the 99-102 range across the Piedmont again
Saturday afternoon.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 145 PM EDT Friday: Saturday night, the approach of a
highly-elongated upper trough should ultimately push a frontal
boundary through the area from the north/northwest, advecting dry
cP air with it.  With the Bermuda High anchored over the western
Atlantic, persistent southeasterly flow will drive a plume of higher
PWATs into the area, inducing isentropic ascent over the cold air.
Ultimately, this leads to the development of a summertime cold air
damming event, with a clear isobaric signature evident in all the
global models by daybreak Sunday.  Throughout Sunday, widespread
cloud cover and precipitation into the cold dome should further
strengthen this in situ CAD.  Consequently, temps should be easily
10 degrees cooler on Sunday than they were on Saturday.  As with
all frontal passages, some thunder is guaranteed.  Model soundings
indicate PWATs in excess of 1.8-2", warm cloud depths of 10-11 kft,
and minimal MBE vectors - making heavy rain the primary threat
from this convection.

This trend continues into Monday.  With cold air entrenched across
the Piedmont and Foothills, the wedge boundary appears to set up
near or south of the southern tier of our CWA.  A slight weakening
in flow off the Atlantic will allow moisture to relapse slightly,
and PoPs drop off a tad accordingly; nonetheless, Sunday and Monday
both entail widespread categorical PoPs across the mountains, with
chance to likely PoPs elsewhere.  Surface heating will be severely
hampered by cloud cover and rainfall, limiting instability; however,
can't rule out some embedded thunder, especially given that robust
upglide should lend itself to elevated convection.  Once again,
heavy rain will be the biggest threat here, and perhaps an uptick
in flash flood threat given that this rainfall will take place
with many areas already saturated by Sunday's rainfall.

Monday evening, moisture should ramp up again as remnants of
Tropical Depression Fred approach from the south.  The brunt of
these impacts, however, will not be felt until past the end of
the short term forecast.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 200 PM EDT Friday: Monday evening, tropical moisture will
arrive in earnest.  Although model guidance remains split on Fred's
track and intensity, these details may not matter much - with a
remnant wedge in place, a focusing boundary just barely south of
the CWA, and robust moisture in place, heavy rain is a guarantee
whether Fred is intact and over our region or falling apart and well
to our west.  Although the ECMWF's excessive totals seem overdone,
it's likely we'll see notable rainfall totals regardless.  So,
for now, keeping the QPF forecast on the high side of guidance;
most models are predicting significant rainfall totals through
Tuesday night, with the GFS being the extremely unimpressed
exception for its last several runs.  Consequently, we anticipate
at least localized hydrological threats on Tuesday, as widespread
heavy rain falls on areas already primed by days of moist weather.

Late in the week, we'll return to the typical summertime diurnal
pattern as southeasterly surface flow is reestablished and
conditions trend back to climatological temperatures.

&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Showers developing on persistent outflows
will require a VCSH mention to be included at KCLT until about 03Z,
but stabilizing profiles suggest the TSRA are done there for the
night. Otherwise, convection will continue to dwindle in line with
the convection-allowing models through late evening and early
overnight. VFR conditions are expected going forward, except for
likely IFR fog/stratus in the mountain river valleys, including
KAVL, and MVFR fog possible at/near KHKY toward daybreak. Cannot
rule out some overnight fog at or near KCLT given the rainfall this
evening, but it might be able to dry out there before the vsby falls
with continued light mixing. The potential for better shower and
thunderstorm coverage looks greater Saturday afternoon and evening
as a front approaches from the north and moisture pools over the
region. Winds will generally remain light SW through the period,
with more variable directions expected at KAVL, and gusty near
thunderstorms late Saturday.

Outlook: Fairly widespread shower and thunderstorm coverage remains
in the forecast for the late weekend and the early to middle part of
next week. Fog and low stratus will be possible each morning,
especially over mountain valleys, and in areas primed by rainfall
from the previous evening. Low restrictions are also likely with any
downpours.

Confidence Table...

            01-07Z        07-13Z        13-19Z        19-00Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     Low   38%     Med   73%     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 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
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...HG

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1024 PM EDT Fri Aug 13 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-150230-
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-
1024 PM EDT Fri Aug 13 2021

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

.DAY ONE...Tonight.

Hazardous weather is not expected at this time.

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

The remnants of tropical cyclone Fred may interact with an old
front to produce heavy rainfall early next week. This could result
in a flash flooding threat, especially in areas that receive
multiple rounds of heavy rainfall.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
746 PM EDT Fri Aug 13 2021

SCZ008-009-140015-
York SC-Cherokee SC-
746 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of western York and
southeastern Cherokee Counties through 815 PM EDT...

At 746 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles southwest of York, or over Sharon, moving northeast at 35 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
York, Sharon, Hickory Grove, Smyrna, Kings Mountain State Park, Kings
Creek and Bullock Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3483 8134 3493 8153 3512 8139 3499 8114
TIME...MOT...LOC 2346Z 232DEG 32KT 3495 8135

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

WJM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
814 PM EDT Fri Aug 13 2021

SCZ009-140045-
York SC-
814 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of western York County
through 845 PM EDT...

At 814 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles west of York, or near Smyrna, moving northeast at 20 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
York, Clover, Sharon, Hickory Grove, Smyrna, Newport, Kings Mountain
State Park and Bethany.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3489 8134 3504 8148 3505 8146 3505 8141
      3508 8141 3516 8126 3516 8123 3501 8108
TIME...MOT...LOC 0014Z 231DEG 17KT 3502 8134

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

WJM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
837 PM EDT Fri Aug 13 2021

NCZ071-072-140100-
Cabarrus NC-Mecklenburg NC-
837 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of western Cabarrus and
central Mecklenburg Counties through 900 PM EDT...

At 836 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Uptown Charlotte, or over University City, moving
northeast at 20 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Downtown Concord, Kannapolis, Northeast Charlotte, West Concord,
Harrisburg, University City, Reedy Creek Park, Charlotte Motor
Speedway, Hidden Valley and Coddle Creek Reservoir.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3519 8073 3533 8087 3547 8069 3535 8049
TIME...MOT...LOC 0036Z 230DEG 18KT 3531 8074

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

WJM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
910 PM EDT Fri Aug 13 2021

NCZ057-072-140145-
Rowan NC-Cabarrus NC-
910 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of northeastern
Cabarrus and southeastern Rowan Counties through 945 PM EDT...

At 909 PM EDT, Doppler radar was tracking a strong thunderstorm near
Downtown Concord, moving northeast at 30 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Downtown Concord, Kannapolis, Rockwell, Mt Pleasant, West Concord,
High Rock Lake and Gold Hill.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3550 8029 3538 8038 3532 8052 3544 8066
      3562 8027 3556 8021 3555 8021 3554 8020
      3553 8020 3552 8018 3551 8018
TIME...MOT...LOC 0109Z 232DEG 24KT 3542 8053

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

WJM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1113 PM EDT Fri Aug 13 2021

NCZ037-057-140345-
Rowan NC-Davie NC-
1113 PM EDT Fri Aug 13 2021

...A strong thunderstorm will impact portions of southwestern Davie
and western Rowan Counties through 1145 PM EDT...

At 1112 PM EDT, Doppler radar was tracking a strong thunderstorm 10
miles north of Kannapolis, or 6 miles south of Cleveland, moving
northeast at 25 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Salisbury, Mocksville, Kannapolis, China Grove, Spencer, Landis,
Cooleemee, Cleveland, Enochville and Granite Quarry.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3551 8064 3559 8075 3568 8077 3592 8061
      3582 8047 3579 8048 3577 8045 3575 8046
      3573 8045 3572 8038 3572 8034 3571 8032
TIME...MOT...LOC 0312Z 220DEG 23KT 3563 8067

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

HG