Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
522 PM EDT Thu Jul 1 2021

.SYNOPSIS...
High pressure off the Atlantic coast weakens as a cold front drops
into the area from the Ohio River Valley on Friday. Increasing
moisture will lead to increasing coverage of showers and
thunderstorms on Friday. The front moves east and south of the area
by Saturday and Independence Day. Near seasonal conditions expected
early next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 500 pm: Pre-frontal training thunderstorms have begun
affecting the far western NC mountains late this afternoon, and
upstream radars and the latest CAMs are suggesting this could well
continue through the evening hours and overnight. Given the rainfall
efficiency suggested by model profiles in the high terrain, it seems
prudent to post a Flash Flood Watch in the Tennessee border counties
of the NC mountains through 12Z Friday. These locations have 3hr FFG
values of 2 to 3 inches, easily achievable with any training and
high rainfall rates, whereas locations along and east of the Blue
Ridge mountains have higher FFG values and probably less potential
for training later tonight through Friday as convection will be a
bit more on the move. The FFA product has already been issued.

Otherwise, the latest SPC Mesoanalysis depicts sbCAPE values around
1500-2000 J/kg late today, with unimpressive mid-level lapse rates
and dewpoints that have again mixed out to the mid-60s across a good
chunk of the area. Nevertheless, scattered cells should continue to
bubble over the next few hours, and resultant outflows should
instigate isolated/scattered activity in the Piedmont very soon.

Attention then turns to the rather impressive height falls
overspreading the Ohio Valley and vicinity and attendant frontal
zone that will begin impacting the area later this evening into the
overnight. The well-forced and very moist (PWATs 1.75-2" during that
time) environment will support maintenance of widespread showers and
at least scattered thunderstorms across the area. High moisture
content/warm cloud depth will support efficient rainfall production
while unidirectional flow oriented roughly parallel to the slow-
moving front will support a favorable scenario for training cells.
An FFA has been posted, as mentioned above.

In terms of the severe threat, such as it is, it should mainly occur
this afternoon/evening with the more discrete/scattered cells, and
be very much of the pulse mode. Waning instability overnight...
along with even weaker upstream instability indicates very little
chance of convection organizing to any great extent...despite wind
shear becoming marginally favorable for such.

Convective chances will steadily taper off from NW to SE across the
area through the morning hours as the better forcing/deeper moisture
shift east. However, with the frontal boundary expected to lag
behind over the forecast area, scattered redevelopment is likely
during the afternoon, mainly across the southeast half. Max temps
will be around 5 degrees below normal, owing largely to extensive
cloud cover that will be stubborn to relent.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH MONDAY/...
As of 300 PM EDT Thursday: At the beginning of the period Friday
night, the cold front is expected to be moving through the
Piedmont such that by Saturday morning, dramatic changes to the
sensible weather will be well underway.  With a sprawling 1020mb
high pressure over the central Mississippi River Valley, a dry
continental airmass will overtake the region, setting us up for a
picture-perfect Independence Day long weekend.  Saturday will be
the blue-ribbon winner of the weekend with the lowest July 3rd high
temperatures since 2015, topping out about 5 degrees below-normal.
With dewpoints plunging into the lower to middle 50s by Saturday
afternoon, humidity values will be very comfortable across the
entire region.

Heading into July 4th, the high pressure will weaken and propagate
slowly east into the Ohio River Valley, keeping our winds light
and variable.  Dewpoints will creep back into the upper 50s
for Sunday and, as the high continues to weaken into Monday,
subtropical high pressure over the Atlantic will dominate our wind
field and weak southerly flow returns.  Therefore, expect another
incremental increase in dewpoints for Monday into the lower 60s,
but still fairly pleasant humidities for July.  Regardless, skies
will remain mostly sunny through the Monday holiday and though
high temperatures warm a couple of degrees each day, by Monday
they are just about normal for this time of year.  All-in-all,
it will be a perfect weekend for festivals and fireworks.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 300 PM EDT Thursday: Of course, all eyes are on tropical
cyclone Elsa for the extended period and her possible path
towards the southeast US, but tremendous uncertainty remains.
At the beginning of the extended on Tuesday, the upper-level
pattern is a bit complex with the Southeast coast underneath a
weakness aloft, a retreating subtropical ridge to the east, and a
shortwave ridge over the Ohio and Tennessee Valleys to the west.
Meanwhile, a strong shortwave trough is digging into the central
Great Plains and the Midwest while Elsa gets drawn into the
weakness between the approaching trough and the retreating ridge.
As is often the case in the midlatitudes, the exact track will be
determined by the speed and amplitude of the incoming trough and
the strength and westward expansion of the subtropical ridge.
Ensemble track guidance from overnight had extreme spread and
the official NHC forecast generally reflects the mean of the
broadly distributed track guidance.  The deterministic 12Z GFS and
Canadian solutions bring Elsa up into the Carolina coastal plain
or coastline Wednesday night through Thursday night, with a ~150
mile spread of the low-pressure center between the two, whereas the
12Z ECMWF continues the solution of previous runs and dissipates
the cyclone over the rugged terrain of Hispaniola.  What is left
of Elsa is absorbed into the offshore stationary front as an open
tropical wave.  Clearly, there is no justification for focusing
on one solution or another this far out and our best advice is to
enjoy your long weekend and keep an eye on the forecast heading
into early next week.

At a broad level, our forecast will gradually become more unsettled
Tuesday through Thursday next week as moisture returns to the
region in advance of the shortwave trough to our west and the
subtropical ridge to our east.  Expect slight chance pops for
Tuesday afternoon increasing to solid chance pops Wednesday
and Thursday.  Generally unsettled conditions may persist into
Friday even if Elsa lifts well to the NE of our region, as the
upper-level trough that settles into our area late next week may be
slow to depart the area.  High temperatures through the extended
are currently forecasted to remain near to slightly above-normal
with humidity values more typical of a subtropical airmass.

&&

.AVIATION /22Z THURSDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Coverage of showers and thunderstorms will
grow most rapidly this evening from KAVL to KHKY, with more
scattered coverage across the Upstate sites and KCLT. Thus, the
TEMPO groups for non-mountain thunder have been moved back a bit in
time to focus more on the late evening and early overnight hours.

Otherwise, a relatively strong cold front will approach the area
from the northwest tonight, with widespread showers and
scattered/numerous thunderstorms expected to accompany the front.
Cigs will also lower steadily late tonight, with IFR likely at most
sites by sunrise. Occasional MVFR/IFR visby can also be expected
during periods of heavier rainfall. Showers/storms will steadily
taper off throughout Fri morning, although scattered redevelopment
may occur during the afternoon, as the front is not expected to
completely clear the area until late in the day. Cigs are expected
to remain restricted at most sites until afternoon.

Outlook: Drying is expected from Saturday into early next week.
Diurnal showers and thunderstorm chances, along with the potential
for mainly mountain valley morning fog/low stratus will return by the
middle of the week.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High 100%     High  94%     High  81%     Med   79%
KGSP       High 100%     High  95%     Med   62%     Med   68%
KAVL       High  94%     Med   79%     Med   71%     High  84%
KHKY       High 100%     Med   69%     Med   77%     High  81%
KGMU       High 100%     High  94%     Low   53%     Med   68%
KAND       High 100%     High  95%     Med   66%     High  84%

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...Flash Flood Watch through Friday morning for NCZ033-048>052-
     058.
SC...None.

&&

SYNOPSIS...DEO
NEAR TERM...HG/JDL
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...HG/JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
452 PM EDT Thu Jul 1 2021

GAZ010-017-018-026-028-029-NCZ035>037-053-056-057-059-062>065-
068>072-082-501>510-SCZ001>014-019-022100-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Alexander-Iredell-
Davie-Buncombe-Catawba-Rowan-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-
452 PM EDT Thu Jul 1 2021

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

.DAY ONE...Tonight.

Showers and thunderstorms will increase in coverage and intensity
from the west tonight ahead of a cold front tonight. Cloud-to-
ground lightning and very gusty winds can occur with any of these
thunderstorms. Areas of heavy rainfall will be possible, potentially
leading to isolated flash flooding, especially across the mountains.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Showers and thunderstorms will cross the area Friday as the cold
front moves southeast across the region. Cloud-to-ground lightning
and very gusty winds may continue with any of the storms. Areas of
heavy rainfall will be possible, potentially leading to isolated
flash flooding. Rainfall will quickly move east of the area Friday
evening.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information
about observed severe weather to the NWS while following all
local, state, and CDC guidelines.

NCZ033-048>052-058-022100-
Avery-Madison-Yancey-Mitchell-Swain-Haywood-Graham-
452 PM EDT Thu Jul 1 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH FRIDAY MORNING...

This Hazardous Weather Outlook is for the Tennessee border counties
of the mountains of western North Carolina.

.DAY ONE...Tonight.

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

   Flash Flood Watch.

In addition to the heavy rainfall threat, the increasing coverage of
thunderstorms will generate cloud-to-ground lightning and very gusty
winds through tonight.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

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

   Flash Flood Watch.

Showers and thunderstorms will cross the area Friday as the cold
front moves southeast across the region. Cloud-to-ground lightning
and very gusty winds may continue to occur with any of the storms.
Rainfall will quickly move east of the area by late Friday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information
about observed severe weather to the NWS while following all
local, state, and CDC guidelines.

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
540 PM EDT Thu Jul 1 2021

NCZ033-501-012215-
Caldwell Mountains NC-Avery NC-
540 PM EDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN CALDWELL AND
SOUTHEASTERN AVERY COUNTIES UNTIL 615 PM EDT...

At 540 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles southeast of Newland, or near B.R. Parkway-Linville Falls To
Grandfather, moving east at 15 mph.

Locations to be impacted include...
Newland, Blowing Rock In Caldwell County, Crossnore, Sugar Mountain,
Grandfather Mountain State Park, B.R. Parkway-Linville Falls To
Grandfather, Linville Falls, Edgemont, Altamont and Pineola.

Wind gusts up to 35 mph and pea size hail 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 3611 8181 3612 8169 3612 8161 3594 8164
      3590 8172 3590 8173 3593 8175 3593 8178
      3595 8178 3595 8180 3597 8182 3598 8187
      3600 8190 3595 8196 3595 8198 3613 8196
      3613 8182
TIME...MOT...LOC 2140Z 276DEG 13KT 3604 8189

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
708 PM EDT Thu Jul 1 2021

SCZ014-012345-
Chester SC-
708 PM EDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN CHESTER COUNTY
UNTIL 745 PM EDT...

At 707 PM EDT, Doppler radar was tracking a strong thunderstorm 13
miles southwest of Lancaster, or near Great Falls, moving northeast
at 35 mph.

Locations to be impacted include...
Great Falls, Fort Lawn and Fishing Creek Reservoir.

Wind gusts up to 45 mph and pea size hail 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.

Fishing Creek Lake is in the path of this storm. Cloud to ground
lightning and gusty winds will create dangerous boating conditions.
Move to shore immediately.

&&

LAT...LON 3467 8089 3463 8090 3462 8089 3460 8089
      3455 8087 3454 8088 3454 8091 3456 8106
      3479 8088 3475 8088 3470 8086
TIME...MOT...LOC 2307Z 207DEG 32KT 3455 8088

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
718 PM EDT Thu Jul 1 2021

NCZ048-012345-
Madison NC-
718 PM EDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL IMPACT MADISON COUNTY UNTIL 745 PM
EDT...

At 718 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles northwest of Marshall, or near Hot Springs, moving east at 30
mph.

Locations to be impacted include...
Marshall, Mars Hill, Hot Springs, Faust, Allenstand, Walnut, Wolf
Ridge and Spring Creek.

Wind gusts up to 40 mph and 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 3603 8259 3600 8261 3597 8261 3595 8256
      3598 8251 3595 8248 3593 8250 3591 8249
      3589 8245 3586 8242 3582 8241 3578 8287
      3593 8291 3595 8285 3592 8282 3597 8278
      3599 8279 3600 8277 3606 8264
TIME...MOT...LOC 2318Z 254DEG 26KT 3587 8279

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
800 PM EDT Thu Jul 1 2021

NCZ071-SCZ009-020030-
Mecklenburg NC-York SC-
800 PM EDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL IMPACT SOUTHERN MECKLENBURG AND
NORTHEASTERN YORK COUNTIES UNTIL 830 PM EDT...

At 759 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles northwest of Indian Land, or near Carowinds, moving northeast
at 35 mph.

Locations to be impacted include...
Uptown Charlotte, Central Charlotte, South Charlotte, Southwest
Charlotte, East Charlotte, Northwest Charlotte, Mint Hill, Fort Mill,
Pineville and Tega Cay.

Wind gusts up to 50 mph and pea size hail 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 3503 8087 3507 8090 3501 8090 3497 8097
      3506 8111 3515 8103 3516 8100 3519 8100
      3532 8089 3519 8061
TIME...MOT...LOC 2359Z 221DEG 29KT 3506 8097

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
833 PM EDT Thu Jul 1 2021

NCZ071-072-020100-
Cabarrus NC-Mecklenburg NC-
833 PM EDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL IMPACT WESTERN CABARRUS AND CENTRAL
MECKLENBURG COUNTIES UNTIL 900 PM EDT...

At 833 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles northeast of Uptown Charlotte, or near Hidden Valley, moving
northeast at 35 mph.

Locations to be impacted include...
Uptown Charlotte, Kannapolis, Downtown Concord, Northeast Charlotte,
East Charlotte, West Concord, Harrisburg, University City, Reedy
Creek Park and The Plaza.

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 3516 8075 3525 8090 3551 8070 3551 8062
      3541 8044
TIME...MOT...LOC 0033Z 218DEG 30KT 3528 8076

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
909 PM EDT Thu Jul 1 2021

NCZ057-072-020145-
Rowan NC-Cabarrus NC-
909 PM EDT Thu Jul 1 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN CABARRUS AND
SOUTHEASTERN ROWAN COUNTIES UNTIL 945 PM EDT...

At 909 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles east of Kannapolis, or 4 miles southwest of Rockwell, moving
northeast at 40 mph.

Locations to be impacted include...
Salisbury, Spencer, Granite Quarry, Rockwell, Faith, High Rock Lake,
Mt Pleasant, Gold Hill and High Rock.

Wind gusts up to 55 mph and pea size hail 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 8044 3552 8061 3573 8043 3573 8039
      3572 8038 3572 8034 3571 8032 3570 8033
      3568 8033 3567 8031 3563 8029 3562 8025
      3558 8021
TIME...MOT...LOC 0109Z 221DEG 33KT 3552 8047

ARK