Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1047 PM EDT Thu Apr 8 2021

.SYNOPSIS...
A cold front will approach slowly from the west tonight into Friday,
with increasing shower and thunderstorm chances. The cold front
finally pushes through the forecast area late Saturday into early
Sunday keeping shower and thunderstorm chances around through
midday. High pressure builds in behind the departing cold front
Sunday into Monday, leading to drier conditions. Another cold front
tracks into the region on Tuesday, but models disagree on the
sensible impacts of this system.

&&

.NEAR TERM /THROUGH FRIDAY NIGHT/...
As of 1025 PM Thursday...RADAR is clear across the CWA save for a couple
of strong to severe cells currently moving eastward out of far NE Georgia
and into the western Upstate. These storms have produced some small hail
and gusty winds thus far, and look like they will survive for a while
longer as they move farther east.

Otherwise, a closed occluded low pressure system will drift NNE across
the Upper Midwest tonight and early Friday, while an upper ridge axis
shifts off the East Coast. A weakening warm conveyor belt associated
with the above low will continue to track across the CWA late tonight
and then wash out over our southern zones on Fri. Sfc-based instability
should continue to wane late tonight and any additional convective
activity should be elevated and sub-severe. There will be some amount
of elevated CAPE thru the overnight across most of the CWA, especially
the Upstate, so a few isolated thunderstorms cannot be ruled out. Any
activity should wane during the the pre-dawn hours. Lows will be about
10-15 degrees above normal under good cloud cover and elevated dewpts.
Friday's fcst still looks tricky. Most of the latest guidance has cloud
cover scattering by mid-morning, with highs back in upper 70s outside
of the mtns. Some mid and high clouds will linger and we will likely
take some time to become unstable. Overall, guidance remains not very
bullish wrt widespread convection tomorrow aftn/evening. Nonetheless,
with another day of moist SLY/SWLY low-lvl flow and sbCAPE peaking in
the 1000 to 2000 J/kg range, we should see some sct convection develop
with the potential for an isolated severe storm or two.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
As of 200 PM EDT Thursday: Lingering showers and thunderstorms will
be in store across portions of the CFWA Friday night before the the
nocturnal cycle gradually diminishes the convective environment
that is introduced Friday afternoon/evening. The pattern remains
amplified going into Saturday as a deepening upper low over the
central High Plains pushes into the mid-MS Valley during the day
Saturday. At the same time, a shortwave trough on the southern
stream portion of the upper low will rotate within the broad
cyclonic flow from the lower MS Valley through the Southeast by
Saturday afternoon. With a stacked ridge setting up shop just
offshore over the western Atlantic, the incoming shortwave will
derail the dry air that was entrained in the mid-levels and
allow for profiles to become more saturated. When factoring in
the arrival of a 30-40+ kt low level jet and daytime heating,
convective development ahead of the cold front will be likely across
the CFWA. With good moisture transport entering the region, PWAT
values ranging between 1"-1.5" could alter convective development
slightly and thus, heavy rain will be the primary threat with any
embedded thunderstorms that form during the afternoon and evening
hours on Saturday.

The pre-frontal activity expected on Saturday will gradually wane by
the nighttime period despite the approaching cold front still
lagging behind over the TN Valley early Sunday morning. A secondary
shortwave is shown swinging from the core of the upper low that is
located over the Midwest and Upper Great Lakes at this point will
enter the Mid South Sunday morning and sweep across the CFWA during
the afternoon and early evening hours on Sunday along with the
attendant cold front. The cold front will propel eastward into the
CFWA during the day on Sunday, but the timing of it will be crucial
to what we see, which can make these types of forecasts tricky. With
the cold front expected to be centered just east of the mountains at
the start of daytime heating and dewpoints remaining around 60F,
areas south and east of I-85 and along the I-77 corridor could
experience another day of convection, but model guidance have been
fairly sparse on simulated reflectivity returns. If the cold front
slow downs just a little bit, then it's possible that widespread
convection could develop, but if it becomes more progressive then
the weather will remain relatively quiet on Sunday. Current trends
indicate that SBCAPE will be on the order of ~500-1000 J/kg, with 30-
40 kts of deep layer bulk shear, and PWAT values around 1" will set
the environment up for convective development ahead and along the
cold front. With more dry air entrained in the mid-levels the
overall storm coverage will likely be capped to only isolated to
scattered before the full fropa takes place between 18z-21z Sunday,
but this is subject to change. Temperatures will be slightly above
normal for highs over the weekend, while lows are expected to be way
above normal each night as values should range in the 50s to near 60
for most locations.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 145 PM EDT Thursday: GFS/ECMWF/CMC all in good agreement that
precip should clear out by Sunday evening, with a weak surface high
building in behind the front.  Aloft, a 500mb ridge pushes in from
the west, suppressing vertical motion until Tuesday.  At this point,
all the models depict an upper low pushing through well north of our
area, across the northern Great Lakes and Canada, and dragging a
cold front through the region Wednesday (where before they'd
depicted this feature earlier, on Tuesday night, models are now
trending toward generally slower progression).  They differ in the
amount of moisture present for this frontal passage; while the GFS
and to some extent the CMC now as well are producing showers with at
least a few hundredths of an inch of QPF, the ECMWF keeps us dry
through the period, with little more than some cloud cover
accompanying the fropa.  For now, keeping chance PoPs across the
region from late Tuesday through Wednesday.  Cool high pressure
builds in on Thursday behind the front, and temps swing from well
above normal on Monday and Tuesday, to around normal on Wednesday,
to at or slightly below normal on Thursday as cooler air filters in
from the northwest.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: Most of the shower activity has moved east
of our fcst area with just a few isolated light showers lingering
in the vicinity of KCLT and KAVL. Once these move out of the area,
we'll likely see a lull in shower activity for the rest of the night
thru early tomorrow. Guidance continues to suggest MVFR to IFR cigs
developing overnight/early tomorrow morning across the Upstate in
the wake of the showers, then gradually mixing out to a VFR cigs
by roughly noon. Another round of showers and tstms is expected to
develop to our south and expand northward tomorrow aftn/evening.
Thus, I kept PROB30s for TSRA at all sites beginning in the 18 to
20z window. Winds should become light over the next few hours but
still favor a SLY direction overall. They will pick back up from
the south by tomorrow aftn and remain SLY thru the evening.

Outlook: Scattered to numerous showers and thunderstorms will be
possible late Friday and into the weekend, leading to associated
flight restrictions, especially under any heavier showers. Drying
returns on Sunday and lingers into early next week.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High 100%     High  98%     High  84%     High 100%
KGSP       High 100%     High  82%     High  82%     High 100%
KAVL       High  98%     High  86%     High 100%     High 100%
KHKY       High 100%     High  90%     High  84%     High 100%
KGMU       High  98%     High  89%     High  90%     High 100%
KAND       High  93%     High  84%     High  83%     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...HG/MPR
NEAR TERM...JPT
SHORT TERM...CAC
LONG TERM...MPR
AVIATION...JPT

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
511 PM EDT Thu Apr 8 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-090800-
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-
511 PM EDT Thu Apr 8 2021

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

.DAY ONE...Tonight.

Isolated thunderstorms are in the forecast thru tonight. The main
threat with any of these thunderstorms will be cloud-to-ground
lightning strikes. One or two of the storms may become strong enough
to pose a damaging wind risk.

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

An isolated severe thunderstorm producing damaging wind and large
hail is possible Friday.

.SPOTTER INFORMATION STATEMENT...

None.

Wimberley

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
919 PM EDT Thu Apr 8 2021

GAZ010-017-090145-
Rabun GA-Habersham GA-
919 PM EDT Thu Apr 8 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT HABERSHAM AND SOUTHWESTERN
RABUN COUNTIES UNTIL 945 PM EDT...

At 918 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 9 miles northwest of
Clarkesville to 6 miles east of Cleveland, and moving east at 15 mph.

Locations to be impacted include...
Clarkesville, Cornelia, Baldwin, Demorest, Mount Airy, Lake Rabun,
Batesville, Seed Lake and Hollywood.

Wind gusts up to 45 mph and half inch hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Half inch hail can cause some damage to vehicles. Consider moving
vehicles to a covered storage area before the storm arrives.

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 3454 8362 3460 8365 3462 8364 3465 8366
      3467 8365 3471 8364 3473 8362 3477 8363
      3479 8346 3450 8345 3449 8346 3449 8354
      3448 8356 3448 8365 3451 8367
TIME...MOT...LOC 0118Z 258DEG 15KT 3470 8365 3457 8365

8

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1000 PM EDT THU APR 08 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0943 PM     HAIL             2 NNW MOUNT AIRY        34.54N 83.52W
04/08/2021  E0.5 INCH        HABERSHAM          GA   PUBLIC

            LOTS OF DIME SIZE HAIL AT A HOME BETWEEN MT AIRY AND
            DEMOREST.

&&

WIMBERLEY

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1012 PM EDT Thu Apr 8 2021

SCZ001-004-005-010-090245-
Greater Pickens SC-Greater Oconee SC-Anderson SC-Oconee Mountains SC-
1012 PM EDT Thu Apr 8 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN ANDERSON...
SOUTHWESTERN PICKENS AND SOUTHEASTERN OCONEE COUNTIES UNTIL 1045 PM
EDT...

At 1012 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles west of Seneca, or near Westminster, moving east at 25 mph.

Locations to be impacted include...
Clemson, Seneca, Walhalla, Central, Pendleton, Westminster, Norris,
Lake Hartwell, Lake Keowee and Townville.

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.

Lakes Keowee and Hartwell are in the path of this storm. Cloud to
ground lightning and gusty winds will create dangerous boating
conditions. Move to shore immediately.

&&

LAT...LON 3458 8312 3476 8312 3480 8271 3453 8272
TIME...MOT...LOC 0212Z 271DEG 20KT 3468 8303

8

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1017 PM EDT THU APR 08 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0940 PM     HAIL             2 SSW DEMOREST          34.54N 83.56W
04/08/2021  E1.00 INCH       HABERSHAM          GA   PUBLIC

            QUARTER SIZE HAIL ON FEATHERWOOD DR IN CORNELIA.

&&

WIMBERLEY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1049 PM EDT THU APR 08 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1030 PM     HAIL             3 ENE MARTIN            34.50N 83.14W
04/06/2021  M1.00 INCH       FRANKLIN           GA   PUBLIC

            FACEBOOK USER REPORTS QUARTER SIZE HAIL IN GUMLOG NEAR
            MARTIN.

&&

WIMBERLEY

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1102 PM EDT Thu Apr 8 2021

GAZ028-SCZ006-010-090345-
Hart GA-Anderson SC-Greater Greenville SC-
1102 PM EDT Thu Apr 8 2021

...STRONG THUNDERSTORMS WITH INTENSE LIGHTNING WILL IMPACT
NORTHEASTERN HART...SOUTHEASTERN GREENVILLE AND ANDERSON COUNTIES
UNTIL 1145 PM EDT...

At 1102 PM EDT, Doppler radar indicated strong thunderstorms with
intense lightning along a line extending from 6 miles southeast of
Clemson to 6 miles north of Hartwell, and moving east at 25 mph.

Locations to be impacted include...
Anderson, Homeland Park, Belton, Williamston, Northlake, Honea Path,
Reed Creek, West Pelzer, Starr and Anderson Airport.

In addition to intense lightning, wind gusts up to 40 mph and pea to
dime size hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with these storms. If outdoors, try
to get indoors or into a hard topped vehicle. Otherwise, stay away
from open areas and isolated high objects such as trees. When
indoors, stay away from windows and doors and avoid using wired
electronic devices. Do not take a shower or bath. Try to unplug
unnecessary appliances before the storms approach.

These storms may intensify, so be certain to monitor local radio and
tv stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

Please report damaging winds, hail, or flooding to the National
Weather Service Greenville-Spartanburg by calling toll free, 1, 800,
2 6 7, 8 1 0 1, or by posting on our Facebook page, or Tweet it using
hashtag nwsgsp. Your message should describe the event and the
specific location where it occurred.

&&

LAT...LON 3443 8298 3467 8275 3466 8221 3457 8224
      3443 8239 3429 8262
TIME...MOT...LOC 0302Z 280DEG 22KT 3464 8272 3445 8292

8