Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
659 PM EDT Sun Jun 6 2021

.SYNOPSIS...
The Bermuda high will hangout in the western Atlantic while a cutoff
low tracks slowly northeast from Oklahoma and across the south-
central United States into the first half of the week. This will
lead to diurnally-driven showers and thunderstorms each afternoon.
The main concern is locally heavy rainfall leading to isolated
runoff issues from these slow moving, heavy rain producing storms.
The Bermuda high gradually weakens mid-to-late week while Gulf
moisture interacts with a frontal boundary sinking south out of
Canada. This will lead to continued afternoon and evening showers
and thunderstorms.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 645 PM Sunday: Numerous showers and thunderstorms have
developed over the Charlotte Metro area this afternoon and continue
to do so this evening. With PWAT values >1.7" and weak to moderate
instability, the convective activity will continue to be a problem
in this area. The storm mode is mostly pulse that is being driven by
a relatively strong outflow boundary that is currently moving from
east-to-west into Cleveland County (NC). Rain rates have been ~1"
in these cells, but a few have produced 2+" rates. A few flood
advisories have been issued for Mecklenburg (NC) and Gaston (NC)
Counties, including a Flash Flood Warning in Mecklenburg where
reports of 1-3+" of rain have been observed. Most of the cells have
a history of back building and essentially have to rain themselves
out, which can take a while in this juicy airmass (~70 degree F
dewpoints). Expect this trend to continue through the evening and
potentially into the overnight hours, with more flash flood products
expected as the severe threat diminishes after sunset.

The forecast area finds itself squeezed between a deep semi-tropical
moisture feed, coincident with good low-level forcing across the TN
Valley and Deep South...and more robust instability closer to the
Carolina coastal plain. As such, widespread precip can be found just
west of and in the eastern zones of the CWA through this evening,
with only very isolated activity covering the western Carolinas. The
best chances over the next 3-6 hours may actually be seen this
evening across the upper Savannah River Valley and vicinity, when
short term guidance generally agrees in lifting a weak short wave
trough toward the area from the Deep South. As such, a brief period
of likely PoPs will be carried there this evening. Chances for
severe convection remain quite limited in light of weak shear and
poor mid-level lapse rates, but still wouldn't completely rule out a
pulse severe storm or two. Locally heavy/perhaps excessive rainfall
will therefore remain the primary threat. Convective coverage should
steadily diminish from late evening through the overnight, with isolated
coverage persisting into the early morning hours. Min temps will again
be roughly 5 degrees above climo.

The deep moisture plume to our west will become better positioned
over the forecast area tomorrow, while forcing will improve a bit as
well as weak short wave troughs continue to approach from the Deep
South. Likely PoPs seem to be a good bet over the entire area by the
end of the day. The severe threat continues to appear limited per
the latest guidance, perhaps even more limited as widespread cloud
cover/cooler temps (forecast maxes right around climo) reduces
instability in comparison with today. However, better coverage of
showers and storms should yield an uptick in the locally heavy
rainfall threat.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 145 PM EDT Sunday: No major changes to the short term
forecast.  A nondescript summertime pattern continues as the CWA
remains sandwiched between a 500mb cutoff low over the Ozarks and
Southern Great Plains, and a broad ridge situated over the Eastern
Seaboard.  Although the low will push a bit northeast through
Tuesday, it will have little effect on our weather pattern and
weaken significantly as the blocking ridge remains entrenched over
the Eastern CONUS. Wednesday, the low will decrease in strength, and
by the end of the short term on Wednesday night it has all but
vanished from model output.

So, there shouldn't be much synoptic forcing to work with.  The
Bermuda High still set up over the Western Atlantic will continue to
induce southerly flow off the Gulf of Mexico for the duration of the
short term, which combined with similar southerly flow at the mid-
levels, should keep the atmosphere ripe with moisture - and
accordingly, we see fairly moist profiles through Tuesday and much
of Wednesday in both GFS and NAM model soundings.

Expecting cloud cover to persist through the forecast period, with
scattered showers around the clock.  Diurnally-driven pulse storms
are possible both afternoons as parcels auto-convect.  Severe
potential should remain low in the absence of any notable wind
shear, although as always a rogue severe cell can't be ruled out.
The primary threat still looks like localized heavy rain: with only
very weak environmental winds, there won't be much steering flow and
many storms could remain practically stationary.  With models still
pushing PWATs close to 2" outside the mountains, such stationary
storms could pose a risk of flash flooding, especially in low-lying
or poorly-drained areas.

Temps should stay a degree or two below normal on Tuesday, but with
ample WAA should climb to around or even a tad above normal by
Wednesday.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 200 PM EDT Sunday: Ridging over the East CONUS finally starts
to break down on Thursday, and mid-level flow veers more westerly.
Without support from aloft, the Bermuda High starts to edge south
and east, so southerly surface flow weakens and we may see somewhat
reduced rainfall on Thursday.  A weak warm frontal boundary will
settle over the southern Ohio Valley late Friday into Saturday, but
is still on track to keep north of our forecast area.  Nonetheless,
this could enhance precip rates a bit through the day.  By this
point in time, surface flow will be westerly ahead of an approaching
weak cold front, and despite a less-robust moisture field the
renewed low-level forcing should keep PoPs in the forecast through
late Saturday.

The forecast looks uncertain past this point.  An increasingly
chaotic pattern is in store, with models in disagreement on even the
broad synoptic pattern.  Temps should be above normal through
Saturday, falling to near normal on Sunday in the wake of the
front.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Convection developed over the CLT terminal
and should remain at -SHRA/VCSH through the rest of the evening. At
all other sites, the convective mention is limited to VCSH or VCTS,
but current radar trends indicate that a TEMPO for -TSRA may be
needed for KHKY as the activity in the CLT Metro area drifts in that
direction. The lone exception is at KAND, where probabilities are
expected to ramp up enough this evening to support a tempo for
SHRA from 01-04Z. Overnight...shower chances are expected to
steadily diminish while cigs should begin to fill in and lower, with
MVFR or IFR conditions expected at most terminals by sunrise.
Periodic visby restrictions (primarily MVFR) are also possible in
showers and in BR late tonight/early Monday. Slight improvement in
conditions is expected at most terminals early Mon afternoon, while
SHRA/TS chances will again ramp up late in the forecast period, so a
PROB30 will be included in the 00Z TAF update.

Outlook: Scattered to numerous, mainly diurnal convective coverage
and associated restrictions persist through much of the week.
Morning fog/stratus are also possible, especially in the mountain
valleys.

Confidence Table...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       High 100%     High  95%     High  86%     High  89%
KGSP       High 100%     High  91%     Med   74%     High  83%
KAVL       High 100%     Med   79%     High  95%     High  83%
KHKY       High  95%     High  91%     Med   70%     Med   72%
KGMU       High 100%     High  91%     Med   74%     High  83%
KAND       High 100%     High  91%     Med   74%     High  89%

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...MPR
NEAR TERM...CAC/JDL
SHORT TERM...AP/MPR
LONG TERM...AP/MPR
AVIATION...CAC/JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
323 AM EDT Sun Jun 6 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-070730-
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-
323 AM EDT Sun Jun 6 2021

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

.DAY ONE...Today and tonight.

General summerlike pulse thunderstorms are expected again today
across the forecast area. The main potential impacts are locally
heavy rainfall leading to isolated runoff issues and cloud-to-ground
lightning with any thunderstorm that develops.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
712 PM EDT Sun Jun 6 2021

SCZ012-019-062345-
Laurens SC-Greenwood SC-
712 PM EDT Sun Jun 6 2021

...STRONG THUNDERSTORMS WILL IMPACT SOUTH CENTRAL LAURENS AND
GREENWOOD COUNTIES UNTIL 745 PM EDT...

At 712 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 15 miles southwest of Newberry to 19 miles north
of Evans, and moving north at 15 mph.

Locations to be impacted include...
Greenwood, Ninety Six, Troy, Lake Greenwood State Park, Lake
Greenwood, Greenwood State Park, Ninety Six Historic Site, Promised
Land, Bradley and Kirksey.

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...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

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 3398 8205 3399 8215 3397 8218 3399 8221
      3402 8224 3397 8231 3407 8233 3424 8211
      3435 8183 3432 8186 3430 8190 3424 8191
      3421 8194 3418 8191 3416 8191 3413 8187
      3409 8192 3396 8201 3395 8205
TIME...MOT...LOC 2312Z 166DEG 11KT 3411 8179 3379 8218

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
718 PM EDT Sun Jun 6 2021

NCZ035-502-062345-
Greater Caldwell NC-Alexander NC-
718 PM EDT Sun Jun 6 2021

...THUNDERSTORMS WITH TORRENTIAL RAINFALL WILL IMPACT WESTERN
ALEXANDER AND EASTERN CALDWELL COUNTIES UNTIL 745 PM EDT...

At 718 PM EDT, Doppler radar indicated thunderstorms with torrential
rainfall along a line extending from 3 miles east of Boomer to 8
miles east of Lenoir. These storms were nearly stationary.

Locations to be impacted include...
Taylorsville, Sawmills, Bethlehem, Hudson, Cedar Rock, Lake Hickory,
Kings Creek, Little River In Alexander County, Ellendale and Vashti.

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 3604 8139 3604 8137 3602 8134 3600 8133
      3603 8127 3604 8120 3603 8118 3603 8117
      3604 8113 3603 8109 3581 8124 3582 8153
      3607 8141 3607 8140
TIME...MOT...LOC 2318Z 124DEG 2KT 3607 8119 3589 8138

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
738 PM EDT Sun Jun 6 2021

SCZ011-012-019-070015-
Laurens SC-Abbeville SC-Greenwood SC-
738 PM EDT Sun Jun 6 2021

...STRONG THUNDERSTORMS WILL IMPACT LAURENS...EASTERN ABBEVILLE AND
GREENWOOD COUNTIES UNTIL 815 PM EDT...

At 738 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 11 miles northwest of Newberry to 5 miles east of
Greenwood to 16 miles south of Abbeville, and moving northwest at 30
mph.

Locations to be impacted include...
Greenwood, Laurens, Abbeville, Clinton, Ware Shoals, Ninety Six,
Joanna, Due West, Cross Hill and Donalds.

Wind gusts up to 35 mph and very heavy rainfall rates up to 2 inches
per hour will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

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 3402 8225 3397 8230 3406 8233 3406 8244
      3408 8249 3418 8257 3451 8223 3466 8200
      3458 8186 3460 8184 3457 8180 3457 8176
      3445 8172 3437 8178 3430 8190 3420 8194
      3419 8192 3412 8203 3397 8218
TIME...MOT...LOC 2338Z 157DEG 26KT 3435 8179 3418 8206 3395 8229

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
749 PM EDT Sun Jun 6 2021

NCZ035-502-070015-
Greater Caldwell NC-Alexander NC-
749 PM EDT Sun Jun 6 2021

...STRONG THUNDERSTORMS WILL IMPACT NORTHWESTERN ALEXANDER AND
NORTHEASTERN CALDWELL COUNTIES UNTIL 815 PM EDT...

At 749 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from near Boomer to 6 miles east of Lenoir, and moving
west at 10 mph.

Locations to be impacted include...
Lenoir, Cedar Rock, Ellendale, Kings Creek and Little River In
Alexander County.

Wind gusts up to 35 mph will be possible in these areas. Torrential
rainfall at rates of 1 to 2 inches per hour may cause minor flooding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

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 3605 8139 3604 8137 3602 8134 3600 8133
      3601 8131 3601 8129 3603 8127 3604 8119
      3602 8117 3583 8134 3591 8157 3607 8141
TIME...MOT...LOC 2349Z 080DEG 9KT 3604 8125 3590 8141

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
810 PM EDT Sun Jun 6 2021

NCZ035-502-070045-
Greater Caldwell NC-Alexander NC-
810 PM EDT Sun Jun 6 2021

...THUNDERSTORMS WITH TORRENTIAL RAINFALL WILL IMPACT NORTHWESTERN
ALEXANDER AND NORTHEASTERN CALDWELL COUNTIES UNTIL 845 PM EDT...

At 809 PM EDT, Doppler radar was tracking a thunderstorm with
torrential rainfall 8 miles southwest of Boomer, or 6 miles northeast
of Cedar Rock, moving slowly north at 10 to 15 mph.

Locations to be impacted include...
Cedar Rock, Ellendale, Kings Creek and Little River In Alexander
County.

Very heavy rainfall rates up to 2 inches per hour will be possible in
these areas. Isolated flooding of low-lying areas may result.

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 3605 8139 3604 8137 3602 8134 3600 8133
      3601 8131 3601 8129 3603 8127 3604 8120
      3603 8118 3588 8129 3596 8151 3603 8149
      3607 8141
TIME...MOT...LOC 0009Z 201DEG 13KT 3598 8136

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
813 PM EDT Sun Jun 6 2021

SCZ006-007-010>012-019-070045-
Laurens SC-Anderson SC-Abbeville SC-Greenwood SC-Spartanburg SC-
Greater Greenville SC-
813 PM EDT Sun Jun 6 2021

...STRONG THUNDERSTORMS WILL IMPACT NORTHWESTERN LAURENS...
SOUTHEASTERN GREENVILLE...SOUTHERN SPARTANBURG...SOUTHEASTERN
ANDERSON...NORTHEASTERN ABBEVILLE AND NORTHWESTERN GREENWOOD COUNTIES
UNTIL 845 PM EDT...

At 812 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 13 miles west of Union to 3 miles northwest of
Abbeville, and moving north at 15 mph.

Locations to be impacted include...
Anderson, Laurens, Abbeville, Spartanburg, Simpsonville, Fountain
Inn, Homeland Park, Belton, Woodruff and Williamston.

Wind gusts up to 35 mph and very heavy rainfall rates of 1 to 2
inches per hour 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 3412 8244 3453 8272 3495 8190 3475 8180
      3460 8185 3460 8184
TIME...MOT...LOC 0012Z 161DEG 14KT 3467 8185 3423 8240

HG