Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
323 AM EDT Sun Aug 1 2021

.SYNOPSIS...
A front will remain nearly stationary from the Gulf coast states to
the North Carolina coast through most of the week. Waves of low
pressure will ride along the front giving our area scattered to at
times numerous showers and a few thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 230 AM EDT Sunday: Afternoon convection has ceased across
the region associated with the stalled frontal boundary to
our south.  With continued deep troughing over the Eastern
Seaboard and a shortwave impinging on the Carolinas, lobes of
DPVA have already begun to ripple across the CWA.  Within the
next few hours, this forcing should begin to ramp up in earnest,
with an attendant surface cold front approaching out of the north
and west.  Convection along this boundary has been underway for
hours, and satellite imagery indicates widespread showers and
thunderstorms across the Tennesee Valley.  As profiles moisten
and westerly upslope flow strengthens, activity should begin in
the southern mountains in the hours before sunrise.  Although the
most intense thunderstorm activity should stay well south and
west of us, we should see at least showers pick up later tonight,
particularly across the southern mountains.  With a moist boundary
layer juiced up by today's moisture advection and continued dry air
aloft, patchy fog has already begun to form at some mountain sites,
and should continue to develop for the next few hours.
With cloud cover increasing later tonight, radiational cooling
should be cut off and thus limit any dense fog concerns.

The frontal boundary will continue to sag southward through the
Carolinas this afternoon.  For many portions of the CWA, it should
be well-timed to take advantage of peak daytime heating;
consequently, convection should be more intense and with better
coverage than what we saw Saturday.  As SBCAPE soars to 1000-1500
J/kg, and sustained synoptic forcing helps remove the remains of a
postfrontal inversion aloft, we'll see showers and thunderstorms
break out across the CWA, especially in the mountains, where terrain
enhancement will further aid in convective initiation.  PWATs will
creep up to at least 1.5", and effective shear will reach 25-30kts
across the Piedmont and foothills.  So, seems like we could see some
retriggering, leading to clusters of heavy rain-producing cells.

As the boundary pushes south of the area, the most intense
convective activity will leave with it.  CAMs depict activity
largely exiting our forecast area to the southeast by 8pm or so,
with perhaps some spotty upslope rain lingering in the mountains
overnight.  Although model profiles indicate very dry upper levels
in the wake of the front, the presence of some mid-level saturation
and thin clouds could somewhat limit fog development during the
predawn hours Monday morning.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 305 AM EDT Sunday: An upper trough remains over the eastern
CONUS through the period as a series of short waves move through the
trough reinforcing it. The best forcing for our area looks to be
Monday night and Tuesday when a more organized short wave moves
through. At the surface, a stalled frontal boundary remains draped
along the Deep South to the Carolina Coast. A series of waves of low
pressure move along the front in response to the short wave
activity. Monday night into Tuesday looks to be the best time for
precip to move back across our area as low level flow turns E to SE
and strengthens bringing copious moisture in from the Atlantic.
Precip, possibly heavy, spreads across the area before diminishing
Tuesday night. Guidance is in disagreement on the potential for
widespread heavy rainfall, but we will need to keep an eye on it.
There will be some thunderstorms Monday and Tuesday, but instability
will be limited. Breezy to windy conditions will be possible with a
tightening pressure gradient around the associated low pressure
center. Highs Monday will be a few degrees below normal with Tuesday
well below normal with the precip and wedge-like surface pattern.
Lows will be near to just below normal Monday night then drop a few
degrees Tuesday night.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 320 AM EDT Sunday: Models are in good agreement on another
shortwave trough riding into and sharpening the large upper trough
over the eastern CONUS Wednesday. The trough crosses the area
Thursday, but yet another wave drops into the OH/TN Valleys Friday
and into our area Saturday. The stalled surface boundary remains in
place through the period with a wave of low pressure moving along it
mainly in the Wednesday night and Thursday time frame, then again
for the Friday and Friday night time frame. While the guidance
agrees on a period of unsettled weather, they disagree the amount of
QPF and whether heavy rain is likely. Do have solid chance PoP off
and on through the period. Highs remain well below normal Wednesday
and Thursday, then begin a warming trend Friday into Saturday. Lows
start out nearly steady below normal then show a warming trend as
well.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: A weak cold front should very soon support
development of scatterd SHRA in the mountains, starting from
4-6am and accompanied perhaps by some high-end MVFR ceilings.
Isolated TSRA is possible in the morning as well, but with
too little coverage for a mention in any of the 06Z TAFs.
Patchy fog has already developed at some mountain sites, but
further development should be limited as sky cover increases the
next few hours.  Lee convergence may reinforce the frontal zone
as it crosses into the Piedmont and Upstate later this morning,
allowing VCSH to prevail across most sites by the early afternoon.
Have included PROB30s for afternoon/evening TSRA with MVFR to IFR
ceilings at most sites as well.  Northwesterly to westerly winds
should prevail throughout the period, with low-end gusts possible
from 16Z to 20Z.  Past 22Z, VCSH will drop out of the forecast as
the front sags south and all sites improve to VFR conditions.

Outlook: SHRA/TSRA will be possible at least in afternoons
through Wednesday.  Fog/low stratus will be possible each morning,
particularly for areas primed by rainfall the previous evening.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  95%     High  99%     Med   76%     High  97%
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...RWH
NEAR TERM...MPR
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...MPR

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1130 PM EDT Sat Jul 31 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-020330-
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-
1130 PM EDT Sat Jul 31 2021

This Hazardous Weather Outlook is for northeast Georgia, 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...Sunday through Friday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
250 AM EDT Sun Aug 1 2021

NCZ051-058-059-062-010715-
Graham NC-Swain NC-Northern Jackson NC-Macon NC-
250 AM EDT Sun Aug 1 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT NORTHWESTERN MACON...
NORTHWESTERN JACKSON...SWAIN AND GRAHAM COUNTIES UNTIL 315 AM EDT...

At 250 AM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 9 miles south of
Gatlinburg to 15 miles northwest of Robbinsville to 11 miles east of
Madisonville to 6 miles north of Ducktown, and moving east at 35 mph.

Locations to be impacted include...
Bryson City, Robbinsville, Sylva, Cherokee, Balsam, Dillsboro, Town
Of Santeetlah, Smoky Mountains-Newfound Gap, Smoky Mountains-Fontana
Area and Lake Santeetlah.

Wind gusts up to 45 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.

&&

LAT...LON 3537 8401 3541 8402 3552 8388 3556 8377
      3556 8350 3563 8339 3558 8317 3551 8318
      3541 8304 3534 8340 3527 8353 3512 8363
      3516 8366 3515 8374 3523 8369 3526 8371
      3525 8385 3522 8396 3523 8400 3531 8404
TIME...MOT...LOC 0650Z 286DEG 29KT 3559 8350 3549 8400 3549 8417 3513
8435

RWH

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
315 AM EDT Sun Aug 1 2021

NCZ051-058-059-062-010745-
Graham NC-Swain NC-Northern Jackson NC-Macon NC-
315 AM EDT Sun Aug 1 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT NORTHWESTERN MACON...
NORTHWESTERN JACKSON...SWAIN AND GRAHAM COUNTIES UNTIL 345 AM EDT...

At 315 AM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 10 miles south of
Gatlinburg to 8 miles northwest of Robbinsville to 8 miles west of
Murphy, and moving southeast at 25 mph.

Locations to be impacted include...
Bryson City, Robbinsville, Cherokee, Town Of Santeetlah, Smoky
Mountains-Newfound Gap, Smoky Mountains-Fontana Area, Lake
Santeetlah, Smoky Mountains-Balsam Mountain, Fontana Lake and Fontana
Village.

Wind gusts up to 45 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.

&&

LAT...LON 3537 8401 3541 8402 3552 8388 3556 8377
      3556 8350 3563 8339 3558 8317 3551 8318
      3546 8313 3546 8309 3526 8359 3515 8369
      3515 8373 3520 8373 3523 8369 3526 8371
      3525 8385 3522 8396 3523 8400 3531 8404
TIME...MOT...LOC 0715Z 293DEG 20KT 3558 8344 3538 8393 3512 8417

RWH

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
426 AM EDT Sun Aug 1 2021

NCZ036-037-010900-
Davie NC-Iredell NC-
426 AM EDT Sun Aug 1 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN DAVIE AND
NORTHEASTERN IREDELL COUNTIES UNTIL 500 AM EDT...

At 425 AM EDT, Doppler radar was tracking a strong thunderstorm 13
miles south of Ronda, or 5 miles northeast of Love Valley, moving
east at 25 mph.

Locations to be impacted include...
Harmony, Love Valley, Sheffield, Union Grove and Olin.

Wind gusts up to 45 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.

&&

LAT...LON 3605 8056 3593 8053 3592 8097 3605 8100
      3606 8098
TIME...MOT...LOC 0825Z 260DEG 22KT 3603 8090

RWH