Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1016 AM EDT Fri Jul 9 2021

.SYNOPSIS...
A weak cold front will support late morning through early evening
showers and thunderstorms across the region. An active mid-
summertime pattern, with a chance of showers and thunderstorms each
afternoon, will develop this weekend and continue into at least
early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 10 AM Friday: We're already seeing a cluster of thunderstorms
make their way into Graham and Swain Counties from Eastern Tenn.
This activity should steadily push eastward into the aftn with
convective coverage expanding in the process. Otherwise, the fcst
appears to be in fairly good shape wrt the earlier onset of
convection.

Over the next 24 hours, the upper pattern is expected to flatten and
deamplify across the region. A weak cold front over the lower OH
Valley region should move in our direction with enough mid/upper
support to keep it moving through tonight. Ahead of the front, model
guidance suggests a favorable environment for thunderstorms to
develop over the western Carolinas and northeast Georgia. Although
the mid/upper forcing doesn't look all that great, the air mass
should sustain mixed-layer CAPE around 1500-2000 J/kg by midday and
enough shear (15-20 kt) to provide for some weak organization.
Expect a handful of strong/severe storms, altho chances are slightly
better to our east. The CAMs develop storms a bit earlier than
usual, so the main threat will be more toward the early part of the
afternoon. The coverage should decrease during the mid/late
afternoon, followed by the frontal passage in the early morning
hours on Saturday. Temps should be slightly above normal.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 315 AM EDT Friday: Model guidance is in good agreement that
upper energy over the northern Rockies will drop into the Central
U.S. and form a closed and temporarily cut-off vertically stacked
low pressure system. Meanwhile the Bermuda high to our east will
retrograde westward while strengthening. The resultant tightening of
surface pressure gradients and 500 mb heights will drive deep layer
moist southerly flow by Sunday. The southerly flow will also help to
activate any lingering weak frontal boundary along or just south of
the area northward as a warm front, likely pushing north of the
region by Sunday. For Saturday, it appears the best shot of diurnal
convection is across the mountains, where there is a better overlap
of sufficient low level moisture and modest mid level lapse rates.
However, weak westerly flow will likely push some of the afternoon
to early evening convection east or southeast into adjacent Piedmont
areas. For Sunday the southerly flow regime with increase upper
heights focused across eastern areas would again support the best
convective coverage over the mountains thanks to weak mechanical
lift and better differential heating. Forcing outside of the
mountains is questionable with marginal capping of the atmosphere
possible due to subsidence associated with the building Bermuda
high. Some guidance focused convective initiation outside of the
mountains across the Midlands of SC possible due to some combination
of an inland penetrating sea breeze front or a weak disturbance.
Regardless of the location of convective initiation, associated
outflow boundaries will likely help to overcome any weak low level
capping, spawning additional convective upstream. Neither day looks
particularly concerning convection-wise, however precipitable water
values nearing two inches Sunday may support a low end, localized
excessive rainfall threat should cells become anchored or train.
Increasing moisture and cloud cover Sunday will largely offset
increasing heights aloft resulting in near climo temperatures both
days.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 330 AM EDT Friday: The aforementioned closed low will become
reabsorbed in the mid-latitude westerlies early next week. The net
result will be to knock down the Bermuda High from roughly 598 to
594 dm will reposition what is left of it over the southeast. The
weak trough passing to our north may drag a weak front into the
region by mid-week, but more likely this boundary will stall just to
our northwest. The diurnally driven active pattern will likely
continue into at least Monday or Tuesday, especially across the
mountains as they will be closer to the associated falling heights.
By mid-week zonal flow takes over with upper ridging focused along
the southeast coast. This may suppress diurnal forced convective
activity, especially south of the mountains across the Upstate of SC
into northeast GA where the flow pattern is less conducive for the
deliverance of afternoon to evening focused ridgetop convection.
Seasonably hot and humid conditions will continue through the period
with afternoon temperature peaking above 90 for many east of the
mountains.

&&

.AVIATION /14Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Starting out with a pesky area of IFR/LIFR
stratus across parts of the CLT metro area this morning. This low
cloud ceiling should scatter out by 13Z or so. A weak cold front
will approach today. Expect cu to develop with minimal heating
after daybreak, eventually resulting in a VFR bkn ceiling by late
morning. Wind will be light SW or WSW ahead of the front. Most
of the model guidance develops showers and thunderstorms across
the region in the late morning to late afternoon hours, so all
sites get a TEMPO group at some point from 15Z to 22Z to handle
the brief restriction. After the main convection moves east, the
wind should bend around to WSW, then NW behind the weak boundary
in the mid evening. We will have to watch for fog developing in
the early morning hours on Saturday.

Outlook: An unsettled pattern, with mainly diurnal convection and
morning stratus/fog, is expected to persist through the weekend
and into early next week.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     Med   61%
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...Munroe
NEAR TERM...JPT/PM
SHORT TERM...Munroe
LONG TERM...Munroe
AVIATION...JPT/PM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
517 AM EDT Fri Jul 9 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-100930-
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-
517 AM EDT Fri Jul 9 2021

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

.DAY ONE...Today and tonight.

Thunderstorms are expected to develop across the region today ahead
of an approaching cold front. Storms will begin to develop this
morning over the mountains and will move east across the foothills
and Piedmont this afternoon. A few of the thunderstorms will be
strong to severe with damaging wind gusts and large hail possible.
Frequent lightning and heavy downpours will also accompany the
storms. The storms should push to the east of the area during the
early part of the evening.

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

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

PM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
937 AM EDT Fri Jul 9 2021

NCZ051-058-091415-
Graham NC-Swain NC-
937 AM EDT Fri Jul 9 2021

...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL SWAIN AND GRAHAM
COUNTIES UNTIL 1015 AM EDT...

At 937 AM EDT, Doppler radar was tracking a strong thunderstorm 13
miles northwest of Robbinsville, or 4 miles west of Smoky
Mountains-Twentymile Creek, moving southeast at 30 mph.

Locations to be impacted include...
Robbinsville, Town Of Santeetlah, Smoky Mountains-Fontana Area, Lake
Santeetlah, Fontana Lake, Fontana Village, Smoky Mountains-Twentymile
Creek, Smoky Mountains-Clingmans Dome, Stecoah and Cheoah.

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.

&&

LAT...LON 3537 8401 3541 8402 3546 8396 3547 8392
      3552 8388 3553 8382 3556 8377 3557 8362
      3556 8352 3537 8364 3526 8378 3530 8402
      3531 8404 3535 8404
TIME...MOT...LOC 1337Z 300DEG 26KT 3550 8393

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1030 AM EDT Fri Jul 9 2021

NCZ051-058-062-091515-
Graham NC-Swain NC-Macon NC-
1030 AM EDT Fri Jul 9 2021

...A STRONG THUNDERSTORM WILL IMPACT MACON...SOUTH CENTRAL SWAIN AND
SOUTHEASTERN GRAHAM COUNTIES UNTIL 1115 AM EDT...

At 1029 AM EDT, Doppler radar was tracking a strong thunderstorm 6
miles east of Robbinsville, moving southeast at 35 mph.

Locations to be impacted include...
Franklin, Bryson City, Nantahala Lake, Fontana Lake, Wesser, Stecoah,
Burningtown, Kyle, Rainbow Springs and Nantahala.

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.

&&

LAT...LON 3540 8371 3544 8336 3537 8333 3533 8334
      3525 8330 3513 8331 3500 8352 3502 8352
      3504 8356 3507 8357 3511 8362 3513 8362
      3514 8365 3515 8365 3515 8372 3517 8374
      3524 8369 3526 8371 3524 8375 3525 8383
TIME...MOT...LOC 1429Z 303DEG 29KT 3529 8370

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1103 AM EDT Fri Jul 9 2021

NCZ051-059-062-063-091545-
Swain NC-Southern Jackson NC-Northern Jackson NC-Macon NC-
1103 AM EDT Fri Jul 9 2021

...STRONG THUNDERSTORMS WILL IMPACT MACON...JACKSON AND SOUTH CENTRAL
SWAIN COUNTIES UNTIL 1145 AM EDT...

At 1103 AM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 5 miles west of Sylva to 5 miles northeast of
Franklin to 14 miles north of Clayton, and moving east at 25 mph.

Locations to be impacted include...
Franklin, Sylva, Cullowhee, Highlands, Balsam, Webster, Dillsboro,
Cashiers, Lake Glenville and the Blue Ridge Parkway from Balsam Gap
To Black Balsam Area.

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.

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 3524 8336 3544 8338 3544 8308 3537 8299
      3529 8292 3524 8293 3516 8300 3513 8298
      3505 8306 3503 8301 3500 8311 3500 8352
      3502 8352 3504 8356 3507 8357 3511 8362
      3513 8362 3512 8364 3514 8365
TIME...MOT...LOC 1503Z 279DEG 23KT 3536 8331 3523 8330 3509 8343

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1113 AM EDT Fri Jul 9 2021

GAZ010-017-SCZ001-091600-
Rabun GA-Habersham GA-Oconee Mountains SC-
1113 AM EDT Fri Jul 9 2021

...STRONG THUNDERSTORMS WILL IMPACT NORTHERN HABERSHAM...RABUN AND
NORTHWESTERN OCONEE COUNTIES UNTIL NOON EDT...

At 1112 AM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 10 miles south of Franklin to 6 miles northeast
of Hiawassee, and moving east at 25 mph.

Locations to be impacted include...
Clayton, Mountain City, Tiger, Dillard, Sky Valley, Lake Rabun, Lake
Burton, Lakemont, Oconee State Park and Black Rock Mountain State
Park.

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 3482 8365 3488 8366 3491 8363 3492 8360
      3494 8360 3495 8355 3499 8355 3500 8311
      3502 8302 3479 8312 3467 8365 3473 8362
      3476 8363 3480 8368
TIME...MOT...LOC 1512Z 288DEG 20KT 3503 8334 3499 8364

HG