Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
204 AM EDT Sun Aug 22 2021

.SYNOPSIS...
An upper-level trough of low pressure will persist along the eastern
seaboard today, with moist air in place over the western Carolinas
and northeast Georgia. The trough will gradually lift northeast into
New England through the early week while a ridge of high pressure
builds into the southeastern United States. The ridge will become
dominant across the southern U.S. mid to late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 145 am EDT: Water vapor satellite imagery and the latest RAP
height fields depict a 500 mb closed low center over the Mid-
Atlantic region early this morning, with an associated trough
extending south through the Carolinas. Radar returns show slowly
moving showers over the southern half of the area where deeper
moisture can be found. Anticipate that early morning shower coverage
should refocus to the southwest mountains with the arrival of a
vorticity lobe in the NW flow aloft, and also due to an 850 mb low
center bringing some measure of upslope and low-level convergence to
the southern mountains. The next vorticity lobe may then impact the
Upper Savannah River area late morning into early afternoon. Then, a
final decent shortwave in the NW flow aloft may move across western
NC later in afternoon and evening. Clouds should keep temperatures a
bit below climo today, but dewpoints mostly in the 70s should permit
1500+ J/kg of sbCAPE with peak heating this afternoon. Cannot
completely rule out a strong to severe thunderstorm today, but heavy
rainfall and associated flooding with any training of showers and
thunderstorms looks to be the larger threat. This is especially the
case in the southern tier where profile precipitable water values
should be around two inches.

Convection should generally decay quickly by late evening. Patchy
dense fog could well become an issue overnight, especially in
locations that receive abundant rainfall late Sunday. Minimum
temperatures will remain slightly above climo.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 130 AM EDT Sunday: Upper trough axis will begin lifting
offshore by the start of the short term period. This will be
replaced by a deepening upper ridge over the Southern Plains and
Lower Mississippi Valley, while a subtropical high strengthens
over the western Atlantic. With dry NW-ly flow filtering in aloft,
as well as additional subsidence with the CFWA sandwiched between
the aforementioned upper ridges. With a weak area of high pressure
setting up shop over the southern and central Appalachians at the
surface, expect for relatively dry conditions across the western
Carolinas and northeast Georgia on Monday, with only isolated
showers and thunderstorms expected during the peak heating of the
day. The chance area will stay mainly confined to the ridgetops
and far southeastern zones of the CFWA. A fairly similar pattern
will be in store for Tuesday, but PoPs will be slightly higher
over the region during the afternoon/evening hours as the Bermuda
High begins to influence the forecast and establishes a return flow
with slightly higher PWAT values over the CFWA. Higher thicknesses
(590+ dm) from the two upper ridges will push temperatures 5-10
degrees above normal for both Monday and Tuesday.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 230 PM EDT Saturday: The western Carolinas and northeast
Georgia will be sandwiched between two high pressure systems
throughout much of the extended. The ridge of high pressure to our
west will retreat back west towards the beginning of the forecast
period while the Bermuda high to our east pushes further west
towards the Southeastern US. PWATs will increase each afternoon
Wednesday into Saturday thanks to the Bermuda high extending over
the area. PWAT values should be around 1.5 inches across the mtns
and 1.7 to 2.0 inches outside the mtns. Both the GFS and ECMWF
continue to show a weak tropical wave east of Florida on Wednesday.
The Bermuda high in the western Atlantic will help steer this
tropical wave towards the Southeast coast. The 12z GFS and ECMWF are
now in somewhat better agreement on the overall track of the
tropical wave, but not on the strength. The GFS keeps the tropical
wave closed while the ECMWF keeps the tropical wave open. Both
models now agree that the tropical wave will track across Florida
late Wednesday into Thursday, before tracking across the Deep South
while ridge of high pressure builds over the south-central East
Coast Friday into Saturday. Since the previous run of the ECMWF had
the tropical wave tracking into the Carolinas, confidence on where
this tropical wave will push inland, as well as the strength of the
wave, remains very low at this time. This tropical wave would lead
to increased shower and thunderstorm chances as well as cloud cover
for the CWA. As a result, high temps would be cooler through the
extended period. High temps Wednesday will remain a a few degrees
above climo, but should drop back to near climo Thursday into
Saturday.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Deeper moisture across the southern half of
the terminal forecast area will require more of a VCSH mention early
today, and then a PROB30 TSRA mention later this afternoon. Boundary
layer moisture should also permit MVFR cigs to steadily fill in
through 09Z, with IFR cigs becoming more likely at the Upstate TAF
sites toward daybreak. KAVL cigs will get locked into the LIFR range
quickly, with IFR vsby in fog expected at times as well this
morning. Low restrictions will be slow to improve today with
abundant mid and high clouds in the northwest flow aloft. Bases will
return to VFR throughout by very late morning or early afternoon,
with restrictions mainly under SHRA/TSRA later in the day. Expect
light winds, toggling south to southwest with weak mixing today,
becoming light to calm again tonight. Restrictions will likely
return tonight with drying aloft and a moist surface layer in place.
Low restrictions will be most likely early Monday morning in
locations that receive appreciable rainfall today and this evening.

Outlook: Slightly drier high pressure will build over the region
through the week. Expect isolated to scattered diurnal showers and
thunderstorms each day, and then overnight restrictions in the
mountain river valleys and in any areas that receive heavy rainfall
the previous day.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High  91%     Med   76%     High  94%     High  99%
KGSP       Med   70%     Med   67%     High 100%     High 100%
KAVL       Med   63%     Med   76%     High  98%     High 100%
KHKY       High  90%     High  91%     High 100%     High  95%
KGMU       Med   65%     Med   79%     High 100%     High 100%
KAND       High  85%     Med   72%     High  87%     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...HG
NEAR TERM...HG
SHORT TERM...CAC
LONG TERM...AP
AVIATION...HG

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1249 AM EDT Sun Aug 22 2021

GAZ010-017-018-026-028-029-NCZ051-052-058-059-062>065-068>072-082-
507>510-SCZ001>014-019-230500-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Swain-Haywood-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
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-
1249 AM EDT Sun Aug 22 2021

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

.DAY ONE...Tonight.

Isolated areas of heavy rainfall will lead to a localized flash
flood threat through portions of the overnight period.

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

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ033-035>037-048>050-053-056-057-501>506-230500-
Avery-Alexander-Iredell-Davie-Madison-Yancey-Mitchell-Buncombe-
Catawba-Rowan-Caldwell Mountains-Greater Caldwell-Burke Mountains-
Greater Burke-McDowell Mountains-Eastern McDowell-
1249 AM EDT Sun Aug 22 2021

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

.DAY ONE...Tonight.

Hazardous weather is not expected at this time.

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

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
901 PM EDT Sat Aug 21 2021

SCZ013-014-220145-
Union SC-Chester SC-
901 PM EDT Sat Aug 21 2021

...A strong thunderstorm will impact portions of Chester and east
central Union Counties through 945 PM EDT...

At 901 PM EDT, Doppler radar was tracking a strong thunderstorm 11
miles southwest of Chester, or 5 miles northeast of Carlisle, moving
southeast at 20 mph.

HAZARD...Winds in excess of 40 mph and small 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...
Chester, Richburg, Chester State Park, Blackstock, Carlisle, Lowrys,
Leeds, Cornwell and Santuc.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3456 8094 3454 8096 3457 8143 3464 8153
      3482 8142 3476 8091
TIME...MOT...LOC 0101Z 302DEG 19KT 3464 8140

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH

JPT

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
922 PM EDT Sat Aug 21 2021

NCZ056-069-502-504-220200-
Lincoln NC-Greater Burke NC-Greater Caldwell NC-Catawba NC-
922 PM EDT Sat Aug 21 2021

...A strong thunderstorm will impact portions of western Catawba,
north central Lincoln, southeastern Caldwell and southeastern Burke
Counties through 1000 PM EDT...

At 921 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles west of Hickory, or near Hildebran, moving southeast at 10 mph.

HAZARD...Winds in excess of 40 mph and small 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...
Hickory, Newton, St. Stephens, Conover, Longview, Sawmills, Granite
Falls, Icard, Hildebran and Connelly Springs.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

LAT...LON 3576 8113 3548 8131 3567 8159 3583 8150
TIME...MOT...LOC 0121Z 294DEG 8KT 3570 8145

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

JPT

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
948 PM EDT Sat Aug 21 2021

NCZ082-SCZ009-014-220215-
Union NC-York SC-Chester SC-
948 PM EDT Sat Aug 21 2021

...A THUNDERSTORM WILL IMPACT SOUTHWESTERN UNION...EASTERN CHESTER
AND SOUTHEASTERN YORK COUNTIES UNTIL 1015 PM EDT...

At 948 PM EDT, Doppler radar was tracking a thunderstorm 8 miles west
of Lancaster, or near Fort Lawn, moving east at 25 mph.

Locations to be impacted include...
Rock Hill, Lesslie, Great Falls, Fort Lawn, Richburg, Andrew Jackson
State Park, Catawba, Fishing Creek Reservoir, Jaars and Edgemoor.

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 3482 8064 3482 8080 3484 8080 3484 8087
      3483 8090 3479 8088 3475 8088 3470 8086
      3464 8090 3456 8087 3454 8088 3455 8101
      3458 8114 3482 8118 3495 8107 3490 8088
      3485 8087 3485 8080 3488 8079 3484 8064
TIME...MOT...LOC 0148Z 283DEG 23KT 3469 8092

JPT

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
215 AM EDT Sun Aug 22 2021

SCZ008-220715-
Cherokee SC-
215 AM EDT Sun Aug 22 2021

...A SERIES OF HEAVY RAIN SHOWERS WILL IMPACT SOUTHERN CHEROKEE
COUNTY UNTIL 315 AM EDT...

At 213 AM EDT, Doppler radar was tracking a series of heavy rain
shower developing 7 miles south of Gaffney, or 5 miles northeast of
Pacolet Mills. These showers were nearly stationary, or redeveloping
in place.

Locations to be impacted include...
Gaffney, Thicketty, Saratt and Draytonville.

Very heavy rainfall rates of 1 to 2 inches per hour will be possible
in these areas. Deep ponding of water in low-lying areas will
result, with rapid rises in area streams and creeks.

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 3487 8148 3488 8152 3487 8156 3489 8159
      3488 8163 3490 8165 3490 8167 3491 8168
      3491 8170 3493 8174 3493 8175 3502 8179
      3507 8163 3497 8148 3494 8149 3494 8147
      3490 8148 3484 8146
TIME...MOT...LOC 0613Z 321DEG 2KT 3496 8167

HG