Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
601 PM EDT Tue Aug 3 2021

.SYNOPSIS...
In situ cold air damming continues into Wednesday leading to well
below normal highs. The wedge should erode late Wednesday into early
Thursday leading to warmer highs on Thursday. The chance for diurnal
scattered showers with embedded thunder continues into tomorrow and
Thursday. Highs will continue to increase gradually throughout the
forecast period. Diurnal shower and thunderstorm chances return this
weekend as a trough tracks across the area.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 525 PM Tuesday: The NE half of the fcst area has seen little
in the way of precip over the past few hours, with most of the
shower activity relegated to far western NC and portions of the
Upstate. We've seen a few isolated lightning strikes from a couple
of cells, but that's been it thunder-wise since late this aftn.
Still expecting shower activity/coverage to gradually diminish thru
the evening and into tonight as we lose daytime heating and the sfc
low shifts NE.

Otherwise, the 500mb pattern is more or less blocked across the
CONUS, with the trough moving little thru Wednesday due to the
monster ridge over the western Atlantic. Consequently the front
lingering near the E Gulf and S Atlantic coasts will remain nearly
stationary. A sfc wave is set to spin up along the front near
Charleston this evening and track NE toward the Outer Banks
overnight. Weak upper convergence behind departing jet streak,
combined with backing low-level flow inland of the developing low,
both suggest a continued decrease in forcing and slowly declining
precip chances thru morning in general. These developments could
lead to strengthening of our wedge-like pattern and it might even
become true CAD. Although forcing won't be much to get excited
about, lapse rates remain pretty good aloft tonight under the trough
and we do have a little upslope in play. The aforementioned
convergence axis near the southern Appalachians does suggest small
PoPs for portions of the western CWA on account of lingering
elevated instability. Elsewhere, a fair amount of cloud cover should
linger with moisture still trapped under subsidence inversion. Mins
end up just a degree or two below climo. Diurnal destabilization
Wednesday will allow the morning mountain PoP to increase thru
afternoon. We will carry a small PoP across the board at peak
heating, with locally heavy rain the main concern from any
convection. Max temps are tricky given the improving CAD factors
tonight, but with most guidance depicting partly to mostly sunny
skies by early afternoon, it's hard to imagine the Piedmont not
reaching at least the lower 80s. For now am advertising values 5 to
8 degrees below normal.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 200 PM EDT Tuesday: A stationary front will be draped across
the southeastern United States coast throughout the short term
forecast period. With this frontal boundary so far to our east, the
highest PWAT values will be confined to the SE coast on Thursday.
Meanwhile, an upper-level trough will be just to our west at the
beginning of the period. This trough will lift north and east while
dampening as it tracks into the Northeastern United States Thursday
into Friday. As a result of the trough lifting NE, ridging in the
western Atlantic will extend into portions of the SE CONUS on
Friday. PoPs will decrease Wednesday night but should increase again
on Thursday as shortwaves track along the base of the trough. Capped
PoPs at a slight chance outside the mtns with chance PoPs across the
mtn zones for Thursday. Friday capped PoPs at chance for the entire
CWA as PWATs look to increase in response to Atlantic ridging
building into the area. Highs Thursday and Friday will be much
warmer compared to today and Wednesday, but should remain a few
degrees below climo.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 200 PM EDT Tuesday: The aforementioned ridge of high pressure
in the western Atlantic should be suppressed to the south and east
as another trough approaches from the west Friday night into early
Saturday. This upper-level trough will track east across the
forecast area early Saturday and has the potential to linger across
the area Sunday. PWATs on Saturday look to remain elevated. Just
have chance PoPs for now as models are not in good agreement on the
placement of QPF. Currently the GFS tries to form a cut-off low
along the southern Appalachians Sunday while the ECMWF has the
trough lifting north and dampening. Due to model disagreement capped
PoPs to a slight chance on Sunday. Early next week, Atlantic high
pressure looks to build in from the south, so have capped PoPs to a
slight chance Monday and chance Tuesday. Highs on Saturday will be
near normal or a few degrees below normal. Otherwise, highs should
be a few degrees above normal Sunday into early next week.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Most of the area remains under MVFR stratocu
cigs associated with a CAD-like easterly flow regime, driven by high
pressure over the NE CONUS. A boundary is evident from satellite
imagery west of KCLT, possibly dividing stable air associated
with the "parent high" from more unstable air to the west. All
sites except KCLT are on the unstable side and will be subject
to scattered SHRA this afternoon. The main impact would be brief
vsby restrictions to MVFR or even IFR. A stray TS is not out of
the question. Most guidance depicts gradual deepening of the mixed
layer such that most sites should be low VFR by late afternoon. The
overall pattern changes little tonight; increasing subsidence over
the high will maintain the CAD-like regime and may even enhance
it. Thus, whatever cloud cover is present at sunset looks likely
to persist into morning. Lowering of VFR to MVFR is even progged
for the lower Piedmont including KCLT. Mountain valley fog also
looks likely, so take KAVL to IFR near daybreak. Diurnally driven
SHRA are expected again Wednesday mainly over the higher terrain;
only KAVL gets a mention as VCSH.

Outlook: The usual chance of diurnal convection returns to the
forecast area from Wednesday thru Friday. Fog/low stratus will be
possible each morning, particularly for the mountain valleys and
areas primed by rainfall from the previous evening.

Confidence Table...

            22-04Z        04-10Z        10-16Z        16-18Z
KCLT       High 100%     High  97%     High  80%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  92%     Med   67%     Low   55%     High 100%
KHKY       High 100%     High 100%     High  95%     High 100%
KGMU       High 100%     High 100%     High  97%     High 100%
KAND       High  95%     High  97%     Med   67%     High  81%

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

&&

.CLIMATE...
RECORDS FOR 08-03

               MAX TEMPERATURE         MIN TEMPERATURE
  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      94 1957     71 1909     72 2010     50 1998
   KCLT      98 2011     68 1909     77 1881     60 1998
                1888                                1985
   KGSP     100 2011     71 1909     75 2010     58 1985

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

SYNOPSIS...AP
NEAR TERM...JPT/Wimberley
SHORT TERM...AP
LONG TERM...AP
AVIATION...JPT/Wimberley
CLIMATE...AP

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
505 PM EDT Tue Aug 3 2021

GAZ010-017-018-026-028-029-NCZ033-048>053-058-059-062>065-SCZ001>007-
010>014-019-042115-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Madison-Yancey-
Mitchell-Swain-Haywood-Buncombe-Graham-Northern Jackson-Macon-
Southern Jackson-Transylvania-Henderson-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Greater Greenville-Spartanburg-Anderson-Abbeville-
Laurens-Union SC-Chester-Greenwood-
505 PM EDT Tue Aug 3 2021

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

.DAY ONE...Tonight.

There remains a token chance of thunderstorms into this evening.
Any storm will be capable of producing brief heavy rain and
occasional cloud-to-ground lightning.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ035>037-056-057-068>072-082-501>510-SCZ008-009-042115-
Alexander-Iredell-Davie-Catawba-Rowan-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-
Cherokee-York-
505 PM EDT Tue Aug 3 2021

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

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
218 PM EDT Tue Aug 3 2021

NCZ059-031900-
Northern Jackson NC-
218 PM EDT Tue Aug 3 2021

...HEAVY RAIN SHOWERS WILL IMPACT NORTHWESTERN JACKSON COUNTY UNTIL
300 PM EDT...

At 216 PM EDT, Doppler radar was tracking a series of a heavy rain
showers 5 miles north of Sylva. These showers were nearly stationary
and redeveloping in the same location.

Locations to be impacted include... The Blue Ridge Parkway from the
Smoky Mountains To Balsam Gap and Cherokee. Rapid stream rises are
expected along Soco Creek.

Very heavy rainfall rates up to one inch per hour will be possible
in these areas. Deep ponding of water will develop in low-lying and
poor drainage 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 3547 8332 3550 8328 3552 8324 3552 8322
      3551 8321 3552 8320 3551 8316 3549 8315
      3549 8314 3546 8313 3542 8318 3539 8327
      3547 8333
TIME...MOT...LOC 1816Z 242DEG 0KT 3545 8323

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
621 PM EDT Tue Aug 3 2021

NCZ062-032300-
Macon NC-
621 PM EDT Tue Aug 3 2021

...HEAVY RAIN SHOWERS WILL IMPACT NORTH CENTRAL MACON COUNTY UNTIL
700 PM EDT...

At 618 PM EDT, Doppler radar was tracking a series of heavy rain
showers 8 miles north of Franklin. These showers were nearly
stationary or redeveloping in place.

Locations to be impacted include...
Cowee and Burningtown. Rapid rises are expected along Cowee Creek,
Shepherd Creek, and tributaries to the Little Tennessee River in
the northeast part of Macon County.

Very heavy rainfall rates of one inch per hour will be possible in
these areas. This will lead to deep ponding of water in low-lying
and poor drainage 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 3530 8346 3533 8343 3532 8342 3533 8340
      3533 8333 3530 8332 3527 8332 3525 8330
      3524 8330 3523 8349 3530 8351
TIME...MOT...LOC 2218Z 169DEG 2KT 3530 8342

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
748 PM EDT Tue Aug 3 2021

NCZ059-040030-
Northern Jackson NC-
748 PM EDT Tue Aug 3 2021

...HEAVY RAIN SHOWERS WILL IMPACT NORTHERN JACKSON COUNTY UNTIL 830
PM EDT...

At 744 PM EDT, Doppler radar was tracking a series of heavy rain
showers developing near Sylva. These showers were nearly stationary
or redeveloping in place.

Locations to be impacted include...Sylva, Balsam, Webster,
Dillsboro, the Blue Ridge Parkway from the Smoky Mountains To Balsam
Gap, Cherokee, Whittier, and Savannah. Rapid stream rises are
expected along Soco Creek, Indian Creek, and Dicks Creek.

Very heavy rainfall rates up to an inch per hour will be possible in
these areas. Expect deep ponding of water in low-lying and poor
drainage 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 3546 8335 3547 8334 3547 8332 3552 8324
      3551 8316 3549 8315 3549 8314 3546 8313
      3546 8310 3544 8308 3542 8305 3529 8332
      3530 8332 3533 8334 3540 8334 3542 8336
TIME...MOT...LOC 2344Z 218DEG 3KT 3543 8324

HG