Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
225 PM EDT Sun Jul 25 2021

.SYNOPSIS...
Air quality should continue improving throughout today. Scattered
showers and thunderstorms remain possible again late this afternoon
into this evening. A weak cold front brings active weather into the
forecast tomorrow and Wednesday, before we return to a typical
summertime pattern toward the weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 145 PM: Convection slower to get going this afternoon
likely due to lower PW values and morning stratocu. Still, meso
analysis shows a moderate to very unstable air mass in place over
the area but very little in the way of shear. Observed DCAPE values
are also quite high. Any storms that form have the potential to
become strong with a few severe storms possible with damaging winds.
Large hail seems unlikely given the very high freezing level and
modest at best mid level lapse rates, despite the large difference
between the freezing level and wet bulb zero height. The lower PW
values would suggest a lower flood threat, but storms will be slow
moving. Isolated heavy rain and flooding would be possible where
storms train or merge. CAM guidance still shows best chance of
convection across the mountains which spread south and east across
the foothills then dissipate across the Piedmont. Have kept these
trends as well.

Convection should diminish this evening in most areas. However,
convection originating from frontal zone draped over the TN and OH
Valleys could waft into western NC throughout the night, while a
W/NW flow could initiate a few cells near the TN border. Chance PoPs
will therefore be carried across portions of the NC mountains
through the night. Mountain valley fog and stratus and patchy fog
expected again. Lows will be a degree or two above normal.

Synoptic and CAM guidance show a better chance of convection overall
for Monday. A weak short wave crosses the area in the WNW flow which
may help push a weak boundary into the area. The right entrance
region of an upper jet moves overhead as well increasing upper
divergence. PW values will be back on the increase with at least
moderate instability developing. DCAPE values may not be quite as
high but bulk shear looks to be higher with the short wave moving
through. Isolated severe storms will be possible. Isolated flooding
remains possible as well even though storms will have decent
movement due to higher PW values and more storms in general. Still
show highest PoP across the mountains and foothills where convection
initiates, but there's a better chance of convection moving south
and east into the Piedmont during the afternoon. Highs will be near
to slightly above normal.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 145 PM EDT Sunday: Broad ridging will be in place over the
western part of the country, with the main ridge axis centered over
the Pacific Northwest.  This pattern appears to slightly amplify
over the course of Tuesday and Wednesday as a trough digs down over
New England and the Mid-Atlantic.  A band of weak upper forcing for
descent may somewhat suppress precipitation on Tuesday, but
shouldn't be nearly enough to overcome the much more robust surface
circulation brought on by a stalling cold front over the CWA.
Guidance depicts a band of low-level convergence draped across the
SC Upstate on Monday night; this feature gradually slides south
and east over the course of Tuesday, weakening significantly as
it does so.  Model wind fields are in line with this, indicating
that the front lingers over the far southern tier of our CWA
through Tuesday evening.  This will result in widespread showers
throughout the day on Tuesday, with some embedded thunder during
the afternoon hours.  Despite fairly high LFCs in most areas, robust
lifting along the boundary, which is discernible even above 850mb,
should be enough to get some parcels to convect in the presence
of good instability across the board.

As the boundary weakens further Tuesday night, it will pull back
northward and any northerly flow that had crept into our CWA will be
replaced by renewed southerly flow and continued influx of moisture
driven by the persistent Bermuda High off the coast.  As the frontal
circulation abates, and continued synoptic suppression limits lift,
stratiform precipitation should ramp down by Wednesday morning.
We'll perhaps see a lull in precip late Wednesday morning, before
the usual diurnally-driven showers pick up that afternoon. PoPs
climb into the chance range across the SC Upstate and perhaps into
the eastern NC Piedmont, as model guidance suggests good instability
here.  Farther north and west, lesser instability combined with
capped profiles on the cool side of the remnant frontal boundary
should inhibit widespread convection.

Expect highs on Tuesday to be a degree or two cooler than this
weekend, with the continued wet pattern and weak northerly
flow on the cool side of the boundary dropping our temps a bit.
By Wednesday, renewed southerly flow and WAA will boost temps
several degrees, and they should climb to at least a couple degrees
above climatology.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 200 PM EDT Sunday: Ridging over the western CONUS will
remain in place as the overall upper pattern continues to amplify.
Heights over the Four Corners and Southern Plains should bump up
a bit even as the trough anchored over the east coast deepens.
Remnants of the boundary over the Southeast should fall apart
entirely by Thursday morning, and heights rise a bit as the
western-U.S. ridge nudges eastward.  After a bit of dry weather on
Thursday, the weekend will see at least one shortwave skirt along
this broader trough and produce another wave of precipitation on
Friday or Saturday, perhaps even into Sunday.  Confidence at this
point is low, as model guidance has not come into good agreement on
the general synoptic pattern, let alone local details.  Sticking
with chance PoPs late Friday and into the weekend for now, but these
details will likely change a bit closer to the weekend.

Temps should stay a few degrees above normal on Thursday and Friday,
as WAA and decent surface heating allow for afternoon temps well
into the mid-90s.  They back off again into the weekend with
increased moisture and renewed rainfall, returning to near-normal
by Saturday.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: MVFR stratocu is scattering out with low VFR
Cu developing. Convection slower to develop today, but still expect
best development across the mountains spreading into the foothills.
Have VCTS in place for these. KCLT has the least chance of seeing TS
but SHRA possible, so VCSH there. Guidance in good agreement on
mountain valley fog/stratus overnight, have it in late at KAVL since
the airport is usually the last location to see it. Guidance in
agreement on restrictions at KHKY but not elsewhere outside of the
mountains. Seems like there should be less chance as the low level
flow is more southwesterly. Given persistence though, have gone with
MVFR at KHKY and SCT MVFR elsewhere for now to indicate the
potential. Expect better coverage of convection all areas Monday, so
PROB30s in place for that. Generally S to SW wind this afternoon
becomes light and variable tonight. s to SW wind on Monday.

Outlook: Diurnal thunderstorm chances will steadily increase through
early in the week, with some drying expected during mid-week. Early
morning fog or low stratus will be possible each day, primarily in
the mountain valleys.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     Med   70%
KGSP       High 100%     High 100%     High 100%     Med   70%
KAVL       High 100%     High  95%     Med   66%     Med   60%
KHKY       High 100%     High 100%     High  87%     Med   64%
KGMU       High  99%     High 100%     High 100%     Med   70%
KAND       High 100%     High 100%     High 100%     Med   70%

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...MPR
NEAR TERM...RWH
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...RWH

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
409 PM EDT Sun Jul 25 2021

NCZ036-037-057-260600-
Iredell-Davie-Rowan-
409 PM EDT Sun Jul 25 2021

This Hazardous Weather Outlook is for the Northwest Piedmont of North
Carolina.

.DAY ONE...Tonight.

Widely scattered showers and thunderstorms will develop across the
area by evening. The potential impacts are cloud-to-ground lightning
and locally heavy rainfall. Isolated flooding or flash flooding is
possible, especially in areas that have received heavy downpours the
last few days.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-028-029-NCZ033-035-048>053-056-058-059-062>065-
068>072-501>510-SCZ001>011-260600-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-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-
409 PM EDT Sun Jul 25 2021

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

.DAY ONE...Tonight.

Scattered showers and thunderstorms will occur across the region
through evening, mainly over the mountains and foothills but also
continuing into the upper Piedmont. The main impacts will be cloud-
to-ground lightning and locally heavy rainfall. Isolated flooding or
flash flooding is possible, especially for areas that have received
heavy downpours the last few days.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ082-SCZ012>014-019-260600-
Union NC-Laurens-Union SC-Chester-Greenwood-
409 PM EDT Sun Jul 25 2021

This Hazardous Weather Outlook is for upstate South Carolina and
Union County North Carolina.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Wimberley

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
354 PM EDT Sun Jul 25 2021

GAZ010-252030-
Rabun GA-
354 PM EDT Sun Jul 25 2021

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL RABUN COUNTY UNTIL 430
PM EDT...

At 353 PM EDT, Doppler radar was tracking a strong thunderstorm over
Clayton. This storm was nearly stationary.

Locations to be impacted include...
Clayton, Mountain City, Tiger, Lake Rabun, Lakemont, Black Rock
Mountain State Park, Tallulah Gorge State Park, Sky Valley and
Tallulah Falls.

Wind gusts up to 40 mph 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.

&&

LAT...LON 3498 8331 3488 8323 3488 8324 3487 8324
      3486 8325 3484 8325 3485 8327 3482 8327
      3483 8329 3482 8331 3481 8330 3479 8332
      3476 8332 3473 8341 3475 8343 3473 8348
      3490 8352
TIME...MOT...LOC 1953Z 337DEG 3KT 3487 8339

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
529 PM EDT Sun Jul 25 2021

GAZ017-018-252200-
Stephens GA-Habersham GA-
529 PM EDT Sun Jul 25 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN STEPHENS AND
CENTRAL HABERSHAM COUNTIES UNTIL 600 PM EDT...

At 528 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles northeast of Clarkesville, or 4 miles south of Lake Rabun,
moving south at 5 mph.

Locations to be impacted include...
Toccoa, Clarkesville, Demorest, Tallulah Falls, Tallulah Gorge State
Park, Hollywood and Turnerville.

Wind gusts up to 40 mph 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.

&&

LAT...LON 3474 8357 3474 8353 3473 8349 3473 8346
      3475 8343 3473 8341 3473 8338 3472 8335
      3468 8334 3468 8332 3467 8331 3457 8326
      3453 8358
TIME...MOT...LOC 2128Z 350DEG 4KT 3469 8346

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
536 PM EDT Sun Jul 25 2021

NCZ502-504-252200-
Greater Burke NC-Greater Caldwell NC-
536 PM EDT Sun Jul 25 2021

...A STRONG THUNDERSTORM WILL IMPACT SOUTH CENTRAL CALDWELL AND
CENTRAL BURKE COUNTIES UNTIL 600 PM EDT...

At 535 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles east of Morganton, or over Drexel. This storm was nearly
stationary.

Locations to be impacted include...
Morganton, Valdese, Drexel, Connelly Springs, Rutherford College,
Lake Rhodhiss and Sawmills.

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 3582 8164 3581 8148 3566 8148 3569 8172
TIME...MOT...LOC 2135Z 012DEG 4KT 3576 8161

ARK