Severe Thunderstorm Warning 285, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
301 PM EDT Sat Aug 12 2023

.SYNOPSIS...
A round of thunderstorms, some strong to severe, will move in
from the west this afternoon and evening. Thunderstorm chances
return Sunday and Monday afternoons, along with hotter and more
humid weather. Monday's heat could be dangerous in the Piedmont
for some individuals. A cold front Monday night and Tuesday will
restore milder and drier weather for mid-week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 230 PM EDT Saturday: Convection developing across the
Cumberland Plateau appears to be taking over as the leading edge of
a loosely organized MCS. This activity is forming in an environment
with over 2500 J/kg of MLCAPE, and 25-30 kt of effective shear with
up to 1000 J/kg of DCAPE. So the expectation now is that tstms
will probably be strong to severe as they enter the NC mountains
later this aftn. A Severe Tstm Watch 635 has been issued for the
NC mountains, the adjacent foothills and most of the Upstate and
NE GA until 00z (8 pm EDT). How much this activity will survive
further east is still a big question mark. The 17z HRRR now has
the strongest storms push SE into NE GA and the Upstate, possibly
still strong. The NC Piedmont seems the least likely to see storms,
given the lowest CAPE and some capping from NWLY downslope 850 mb
flow, but slight chc PoPs will be retained there. The main threat
will be damaging wind gusts, but isolated hail up to 1"-diameter
will also be possible.

Convection should wane this evening, as an upper-level shortwave
exits to our east. Mountain valley fog is expected, with patchy
fog possible elsewhere. Lows will be slightly above normal, mainly
in the upper 60s in the mountain valleys to mid 70s in the lower
Piedmont.

A slight building of heights from the large subtropical ridge
should help suppress convection somewhat Sunday. Low-level flow
will be weak, and generally backing to WSWLY, resulting in less
downslope. Guidance is showing less mixing of the dewpts during
the aftn, and with highs getting into the mid 90s, we could see
plenty of 105-109 heat indices across the Upper Savannah Valley
and just south and east of Charlotte. Given that just a deg or
two difference in the temp or dewpt could keep us below advisory
criteria, we will hold off on an advisory with this forecast package
and let the midnight shift assess the latest guidance. Otherwise,
expect isolated to widely scattered convection across the Piedmont
and scattered storms across the mountains, with a couple of pulse
severe storms possible.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 245 PM Saturday: Monday is looking very similar to
Sunday. We're left with convective scraps that die off Sunday
evening while a lead short wave moves past to the north. The
upper pattern remains flat into Monday with somewhat uncertain
evolution of an MCS over the Cumberland Plateau and central
Appalachians. However, consensus is that we should be in a warm
sector of sorts with more than adequate instability to support
thunderstorms developing by afternoon. The fcst has precip probs
close to climo. The storm chances look good over the mtns, but
a cap east of the mtns on fcst soundings supports limiting to a
slight risk. The big problem for Monday will be the temps and heat
index. Altho high temps might only be on the order of five degrees
above normal...well short of records...the dewpoint climbs a bit
more into the middle 70s which suggests a good bet for at least a
Heat Advisory for a large part of the area east of the mtns. Some
places might reach Warning criteria along/S of I-85. Only concern
is how such a plan could go awry with convective debris or early
storm development keeping us from getting warm enough. That leads
us into Tuesday, when model guidance suggests a cold frontal
boundary will be dropping down across the forecast area during
peak heating. The guidance affords us an excellent opportunity to
develop an environment with sufficient buoyancy and shear to support
organized severe storms along/S of the front Tuesday afternoon/eve
east of the mtns. Temps drop off a few degrees which may take care
of the heat advisory concern at least.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 227 PM Saturday: The cold front is expected to push E/SE
of the fcst area by sunset on Tuesday, or shortly thereafter, as
a shortwave moves east and past to our north. High pressure will
build in from the northwest behind the front for the middle part
of the week, with drier and cooler air bringing some relief. The
model trend is toward temps being a few degrees below normal for the
rest of the work week as the high slides past. What is uncertain
is how quickly our usual diurnal convection returns, because
of big differences in how the guidance handles the evolution of
a mid/upper trof late in the week. The ECMWF and Canadian keep
a relatively deep trof axis off to our west through the end of
the period that keeps a west/northwest flow into the region thru
Friday that would be inhospitable to deep convection. The GFS
is more muddled and shows a weak upper low cutting off to our
west that would bring moisture back by Friday. The ECMWF/Canadian
look preferable at this point, but the forecast will end up with
an unmentionable slight risk for late week because of the model
blend. Expect changes as agreement improves.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Low confidence forecast with an approaching
cluster of thunderstorms crossing central TN at time of 18z TAF
issuance. The last few runs of the HRRR have consistently brought
some of that convection across the mountains and into the Piedmont
this evening. However, confidence of it reaching CLT, as anything
more than a few dying showers is still too low to mention in a
TEMPO. However, amendments will be made if trends change. KAVL
and the Upstate sites have slightly better chances of TS, so
will mention with VCTS for now. Debris cloudiness should slowly
thin overnight, leaving mostly clear skies with light winds. The
mountain valleys stand a good chance to fog up again overnight,
while patchy fog will be possible across the Piedmont. Not expecting
as much fog as this morning.

Outlook: Daily shower and thunderstorm chances with associated
restrictions will continue the rest of the weekend and thru the
first half of next week. Mountain valley fog/low stratus will
be possible each morning. Drier conditions expected to return
Wednesday.

&&

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

&&

SYNOPSIS...PM
NEAR TERM...ARK
SHORT TERM...PM
LONG TERM...PM
AVIATION...ARK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
257 PM EDT Sat Aug 12 2023

GAZ010-NCZ033-048>053-058-059-062>065-501-503-505-507-509-SCZ101>103-
131900-
Rabun-Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Caldwell Mountains-Burke Mountains-McDowell Mountains-
Rutherford Mountains-Polk Mountains-Oconee Mountains-
Pickens Mountains-Greenville Mountains-
257 PM EDT Sat Aug 12 2023

...SEVERE THUNDERSTORM WATCH 635 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...This afternoon and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

Scattered to numerous thunderstorms are expected to move in from the
west late this afternoon or early this evening. Some of the
thunderstorms will have the potential to produce severe weather in
the form of damaging wind gusts of up to 60 mph and hail. Any of the
storms may produce cloud-to-ground lightning, gusty winds, and
torrential downpours. The storms should weaken or move east of the
mountains by late evening.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ029-NCZ035>037-056-057-068>072-082-SCZ008-009-011>014-019-131900-
Elbert-Alexander-Iredell-Davie-Catawba-Rowan-Cleveland-Lincoln-
Gaston-Mecklenburg-Cabarrus-Union NC-Cherokee-York-Abbeville-Laurens-
Union SC-Chester-Greenwood-
257 PM EDT Sat Aug 12 2023

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

.DAY ONE...This afternoon and tonight.

Scattered thunderstorms today may produce cloud-to-ground lightning
and gusty winds. A stray storm or two could produce minor wind
damage, mainly this evening.

Also, heat index may rise into the upper 90s or lower 100s this
afternoon, mainly over northeast Georgia, Upstate South Carolina,
and the Charlotte metro area. This could pose a risk of heat-related
illness in some people.

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

Heat index Sunday afternoon is likely to rise into the lower 100s in
many locations, possibly above 105 in some spots. Still hotter and
more humid weather is expected Monday afternoon, when heat index may
rise above 110. These conditions being more likely to cause heat
illnesses, a Heat Advisory or even an Excessive Heat Warning could
be
issued Sunday and/or Monday.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ017-018-026-028-NCZ502-504-506-508-510-SCZ010-104>109-131900-
Habersham-Stephens-Franklin-Hart-Greater Caldwell-Greater Burke-
Eastern McDowell-Greater Rutherford-Eastern Polk-Anderson-
Greater Oconee-Greater Pickens-Central Greenville-
Southern Greenville-Northern Spartanburg-Southern Spartanburg-
257 PM EDT Sat Aug 12 2023

...SEVERE THUNDERSTORM WATCH 635 IN EFFECT UNTIL 8 PM EDT THIS
EVENING...

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

.DAY ONE...This afternoon and tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

Scattered thunderstorms today may produce cloud-to-ground lightning
and gusty winds. A stray storm or two could produce minor wind
damage, mainly this evening.

Also, heat index may rise into the upper 90s or lower 100s this
afternoon, mainly over northeast Georgia, Upstate South Carolina,
and the Charlotte metro area. This could pose a risk of heat-related
illness in some people.

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

Heat index Sunday afternoon is likely to rise into the lower 100s in
many locations, possibly above 105 in some spots. Still hotter and
more humid weather is expected Monday afternoon, when heat index may
rise above 110. These conditions being more likely to cause heat
illnesses, a Heat Advisory or even an Excessive Heat Warning could
be
issued Sunday and/or Monday.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
323 PM EDT Sat Aug 12 2023

NCZ051-059-122015-
Swain NC-Northern Jackson NC-
323 PM EDT Sat Aug 12 2023

...A strong thunderstorm will impact portions of north central
Jackson and northeastern Swain Counties through 415 PM EDT...

At 323 PM EDT, Doppler radar was tracking a strong thunderstorm 11
miles northeast of Bryson City, or near Smoky Mountains-Oconaluftee,
moving east at 15 mph.

HAZARD...Wind gusts up to 50 mph and half inch 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...
Smoky Mountains-Oconaluftee, Smoky Mountains-Balsam Mountain,
Cherokee, B.R. Parkway-Smoky Mountains To Balsam Gap, Smoky
Mountains-Newfound Gap and Smoky Mountains-Deep Creek.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Severe Thunderstorm Watch remains in effect until 800 PM EDT for
western North Carolina.

&&

LAT...LON 3561 8339 3559 8318 3558 8317 3556 8316
      3554 8317 3553 8317 3551 8318 3550 8318
      3545 8320 3552 8341
TIME...MOT...LOC 1923Z 282DEG 12KT 3554 8330

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

TW

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Special Weather Statement
National Weather Service Greenville-Spartanburg SC
403 PM EDT Sat Aug 12 2023

NCZ059-062-063-122045-
Southern Jackson NC-Northern Jackson NC-Macon NC-
403 PM EDT Sat Aug 12 2023

...A strong thunderstorm will impact portions of east central Macon
and central Jackson Counties through 445 PM EDT...

At 403 PM EDT, Doppler radar was tracking a strong thunderstorm 9
miles east of Franklin, or 4 miles northwest of Lake Glenville,
moving southeast at 15 mph.

HAZARD...Wind gusts up to 50 mph and half inch 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...
Franklin, Cashiers, Lake Glenville, Cullowhee, Highlands, Ellijay,
Tuckasegee, Whiteside Mountain and Cullasaja.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Severe Thunderstorm Watch remains in effect until 800 PM EDT for
western North Carolina.

&&

LAT...LON 3517 8347 3531 8316 3524 8299 3505 8313
TIME...MOT...LOC 2003Z 299DEG 13KT 3520 8322

MAX HAIL SIZE...0.50 IN
MAX WIND GUST...50 MPH

TW