Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1036 PM EDT Thu Mar 25 2021

.SYNOPSIS...
A vigorous cold front is expected to move through the area later
tonight and into Friday and could produce isolated strong to severe
convection along with significant rainfall. The active pattern
continues this weekend as another cold front slides through the
area on Sunday bringing another round of showers and thunderstorms.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 1025 PM Thursday: The cold front was pushing through central
TN and AL with more discrete convection continuing to fire ahead of
it. A couple of these cells tried and failed to hold together as
they pressed into far northeast GA largely due to them running
into the more stable environment. The latest SPC HRRR shows that
later discrete cell should hold together into the western
Carolina's and especially northeast GA as a tongue of 500-1000
CAPE noses into the area from the south thanks to increasing
southerly flow ahead of the front. Feel this could be a bit
overdone but with impressive shear and helicity values should be
enough for at least a few super cell thunderstorms capable of
damaging winds, an isolated tornado, and perhaps large hail.
This threat should be mainly west of I-26 and between roughly
midnight and 4 am. Flood concerns will continue especially for
the southwest mountains. Rainfall totals have already exceeded
5-6 inches at some higher elevations with an additional 1-2
inches possible before all is said and done. The Flash Flood
Watch has been updated accordingly.

As of 830 PM Thursday: The latest surface analysis shows what
appears to be a weak insitu-wedging roughly along and north of I-85
this evening that developed from the steady rainfall from earlier
today. This is indicated by weak high pressure nosing southwest from
the NC Piedmont towards northern GA. This will limit surface based
CAPE and instability overall for this area. This combined with
gradually diminishing upper support as the parent low moves
northeast into the Great Lakes and loss of daytime heating should
limit the coverage of severe thunderstorms compared to neighbors to
our west. That being said SPC recently issued a Tornado Watch for
much of northern GA good through 2 am, just to our west, so we will
be watching the developing situation closely. On that note, high
values of shear/helicity will continue along and ahead of the cold
front, so it probably won't take much instability to maintain strong
to severe thunderstorms (a high shear/low cape environment). Steady
rain with embedded heavy rain will likely continue especially near
the southwest mountains overnight. So we will likely see additional
flooding during this time with the current Flash Flood Watch
seemingly well placed for the time being.

Otherwise, we remain under a weak WAA regime and influence of a
subtropical ridge off the SE Coast. This ridge is downstream of an
expansive trough, within which a potent shortwave will move today,
driving development of a low pressure system over the lower MS
Valley. A significant severe outbreak is expected over portions of
the TN, MS, and AL. Fairly brisk southerly flow has already
initiated convection over the high terrain. The depth and strength
of moisture advection will be impressive, leading to PWATs peaking
near +3 SD, and IVT parameter values that are also anomalously
large. Deep layer hodographs will already be long and curving, but
midlevel lapse rates are not the greatest; the limited instability
will keep our severe threat comparatively small during the day, with
convective layers too shallow to realize all the shear. This does
somewhat limit our heavy rain threat as well, though there will be
widespread coverage and potential for multiple rounds thru tonight.
WPC Day 1 ERO includes most of our SW mtns in a Moderate Risk,
partly because of the aforementioned anomalies and high
probabilities for significant rain rates from the HREF. We are
hoisting a Flash Flood Watch from 18z today to 12z Fri. The same
southerly flow will lead to rather gusty winds, and higher
elevations of the mtns will be exposed to near Wind Advisory-level
conditions.

LLJ is expected to precede the cold front into our area in the
early evening, again enhancing precip generation along the srn
end of the Appalachians; a narrow tongue of sfc based instability
will linger until the front itself enters in the late evening. A
convective line, likely with some embedded rotation will support
vague supercell structure. The dynamic lift provided by the
shortwave will mostly miss our area to the NW as the wave tracks
north of the OH River; this coupled with the unfavorable timing,
and diminishing instability, should begin to impact the convection
particularly as it crosses the mountains. Nevertheless, a narrow
line of strong showers with a few embedded tstms could progress
across the area overnight. Prog soundings reveal that the line will
encounter poor low to midlevel lapse rates, and this would limit sfc
based updrafts and thus tornado risk. The SPC slight risk extending
only into the mtns looks well-placed and even extended slightly
further east. Recent short-term consensus PoPs as well as hourly
NBM seem to be keying better on the shadowing effect of the mtns,
and timing/chances have been revised thru tonight in new fcst grids.

The frontal boundary should push out of the region by 18z Friday
as sfc high builds in to the NW and we enter a post-frontal
environment by the very end of the forecast period. Drier weather
will prevail, with highs in the low 80s in most locations outside
the mountains and 70s in the higher elevations. One factor that
can play a role is how fast the cold front exits the region and
allows for the clouds to scour out.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 145 PM EDT Thursday: the short term picks up at 00Z Saturday,
with a shortwave trough rounding the broader ridge sitting over the
east coast.  By this time, forcing from the trough will largely
be tapering off to the north of our CWA, and a brief bout of
dry weather is in store for Friday night.  Renewed southwesterly
flow over the Tennessee Valley will pump Gulf moisture into the
lower troposphere through the day Saturday, working with weak
mid-level forcing to produce scattered afternoon showers across TN,
spreading into the Blue Ridge Mountains and western SC Upstate
by late Saturday afternoon.  The developing surface low skirts
its way northeast along the Appalachians and drags a cold front
across our area early Sunday afternoon.

Ample WAA ahead of this front paired with decent solar insolation
should prime the environment for convection, with the Piedmont
and Upstate seeing SBCAPE values in the 500-1000 J/kg range and a
40-50kt LLJ riding out ahead of the frontal boundary.  Given the
timing of the frontal passage in the early afternoon, this is a
pattern to keep an eye on over the next day or two.  Some precip
may still be falling for at least the eastern part of our CWA by
the end of the short term at 00Z Monday, as the front tapers off
to the east.

Temps are on track to stay several degrees above normal on Saturday
and Sunday, before dropping back to near-normal Sunday night in
the wake of the cold front.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 200 PM EDT Thursday: by Sunday night, good mid-level forcing
associated with the latest trough is exiting the region to the east,
and precip drops off overnight behind the departing cold front.
We then enter a weak upper ridging regime as high pressure builds
in at the surface.  So, Monday should be dominated by clear,
dry weather as the frontal boundary stalls well south of us.

Meanwhile, the GFS and ECMWF depict a closed upper low meandering
out of the Southern Plains and causing coastal cyclogenesis along
the stagnant frontal boundary.  The resulting surface low tracks
from the Gulf Coast out to the NC/SC coastline.  It looks to only
graze our CWA at this point, yielding chance PoPs on Tuesday
afternoon and overnight.  On Thursday, yet another surface low
pushes into the region from the west, bringing another bout of
rainfall to the region to cap out the week.

Temperatures on Monday and Tuesday look to be a couple degrees
below normal, before southerly WAA brings them back to near-normal
later in the week.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Below normal confidence in 00Z TAFs due to
uncertainty in timing and strength of convective line to move
through the area from west to east between roughly 05Z and 15Z.
Steady rain with isolated TSRA is expected ahead of this feature
with IFR and lower cigs/vsbys likely in heavier shra/tsra. Front may
stall south of TAF sites into Friday with little if any impact to
terminals.

Outlook: Another system may bring showers Saturday with
thunderstorms possible by Sunday.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High  86%     High  97%     High  81%     High 100%
KGSP       Med   77%     Med   61%     High 100%     High 100%
KAVL       Med   73%     Med   60%     High 100%     High 100%
KHKY       Med   67%     Med   72%     High 100%     High 100%
KGMU       Med   79%     Med   72%     High 100%     High 100%
KAND       High  87%     High  86%     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...Flash Flood Watch until 8 AM EDT Friday for GAZ010.
NC...Flash Flood Watch until 8 AM EDT Friday for NCZ051-052-058-059-
     062>064.
SC...None.

&&

SYNOPSIS...MPR
NEAR TERM...CAC/Munroe
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...Munroe

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
445 AM EDT Thu Mar 25 2021

GAZ010-NCZ059-062>064-260845-
Rabun-Northern Jackson-Macon-Southern Jackson-Transylvania-
445 AM EDT Thu Mar 25 2021

...FLASH FLOOD WATCH IN EFFECT FROM 2 PM EDT THIS AFTERNOON THROUGH
FRIDAY MORNING...

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

.DAY ONE...Today and 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.

Additionally, scattered thunderstorms will occur at times through
tonight. Any thunderstorm will be capable of cloud-to-ground
lightning. Late this afternoon and this evening, thunderstorms may
move in from Tennessee which will pose a risk of damaging winds and
hail up to 1 inch in diameter, and a small risk of a tornado.

.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.

.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.

NCZ051-052-058-260845-
Swain-Haywood-Graham-
445 AM EDT Thu Mar 25 2021

...FLASH FLOOD WATCH IN EFFECT FROM 2 PM EDT THIS AFTERNOON THROUGH
FRIDAY MORNING...

This Hazardous Weather Outlook is for western North Carolina.

.DAY ONE...Today and 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.

Additionally, scattered thunderstorms will occur at times through
tonight. Any thunderstorm will be capable of cloud-to-ground
lightning. Late this afternoon and this evening, thunderstorms may
move in from Tennessee which will pose a risk of damaging winds and
hail up to 1 inch in diameter, and a small risk of a tornado.

.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.

Saturday night and early Sunday, another round of thunderstorms is
expected. These storms also may produce severe weather in the form
of damaging wind and large hail.

.SPOTTER INFORMATION STATEMENT...

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

GAZ017-018-026-028-029-NCZ053-065-501>510-SCZ001>006-010-260845-
Habersham-Stephens-Franklin-Hart-Elbert-Buncombe-Henderson-
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-Anderson-
445 AM EDT Thu Mar 25 2021

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

.DAY ONE...Today and tonight.

Scattered thunderstorms will occur at times through tonight. Any
thunderstorm will be capable of cloud-to-ground lightning. Tonight,
a line of thunderstorms will move in from the west, posing a risk of
damaging winds and hail up to 1 inch in diameter, and a tornado
cannot be entirely ruled out.

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

No hazardous weather is expected at this time.

.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>050-260845-
Avery-Madison-Yancey-Mitchell-
445 AM EDT Thu Mar 25 2021

This Hazardous Weather Outlook is for western North Carolina.

.DAY ONE...Today and tonight.

Scattered thunderstorms will occur at times through tonight. Any
thunderstorm will be capable of cloud-to-ground lightning. Late this
afternoon and this evening, thunderstorms may move in from Tennessee
which will pose a risk of damaging winds and hail up to 1 inch in
diameter, and a small risk of a tornado.

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

Saturday night and early Sunday, another round of thunderstorms is
expected. These storms also may produce severe weather in the form of
damaging wind and large hail.

.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.

NCZ082-SCZ014-019-260845-
Union NC-Chester-Greenwood-
445 AM EDT Thu Mar 25 2021

This Hazardous Weather Outlook is for lower piedmont North Carolina
and upstate South Carolina.

.DAY ONE...Today and tonight.

Scattered thunderstorms will occur at times through tonight. Any
thunderstorm will be capable of locally heavy rain and cloud-to-
ground lightning.

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

The severe weather risk will continue until the line of storms moves
out Friday morning. Damaging winds would be the main concern Friday
morning.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ035>037-056-057-068>072-SCZ007>009-011>013-260845-
Alexander-Iredell-Davie-Catawba-Rowan-Cleveland-Lincoln-Gaston-
Mecklenburg-Cabarrus-Spartanburg-Cherokee-York-Abbeville-Laurens-
Union SC-
445 AM EDT Thu Mar 25 2021

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

.DAY ONE...Today and tonight.

Scattered thunderstorms will occur at times through tonight. Any
thunderstorm will be capable of locally heavy rain and cloud-to-
ground lightning.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
654 PM EDT Thu Mar 25 2021

NCZ068-508-510-SCZ007-008-252345-
Greater Rutherford NC-Cleveland NC-Eastern Polk NC-Cherokee SC-
Spartanburg SC-
654 PM EDT Thu Mar 25 2021

...STRONG THUNDERSTORMS WILL IMPACT SOUTHEASTERN RUTHERFORD...
SOUTHEASTERN POLK...SOUTHWESTERN CLEVELAND...NORTHERN SPARTANBURG AND
NORTHWESTERN CHEROKEE COUNTIES UNTIL 745 PM EDT...

At 654 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 7 miles northeast of Columbus to 11 miles west of
Spartanburg, and moving east at 40 mph.

Locations to be impacted include...
Spartanburg, Gaffney, Forest City, Boiling Springs SC, Boiling
Springs NC, Duncan, Lyman, Cowpens, Wellford and Inman.

Wind gusts up to 40 mph will be possible in these areas.

LAT...LON 3546 8158 3500 8164 3483 8220 3484 8221
      3526 8216
TIME...MOT...LOC 2254Z 248DEG 36KT 3529 8208 3493 8213

LANE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1106 PM EDT Thu Mar 25 2021

SCZ007-260330-
Spartanburg SC-
1106 PM EDT Thu Mar 25 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHERN SPARTANBURG COUNTY
UNTIL 1130 PM EDT...

At 1106 PM EDT, Doppler radar was tracking a strong thunderstorm 13
miles west of Spartanburg, or near Lyman, moving east at 40 mph.

Locations to be impacted include...
Spartanburg, Boiling Springs SC, Duncan, Lyman, Cowpens, Wellford,
Inman, Mayo, USC Upstate and Lake Bowen.

Wind gusts up to 45 mph will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm 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.

&&

LAT...LON 3507 8222 3514 8185 3506 8181 3504 8181
      3503 8179 3495 8176 3492 8222
TIME...MOT...LOC 0306Z 257DEG 36KT 3500 8215

LANE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1142 PM EDT Thu Mar 25 2021

NCZ068>070-SCZ008-009-260430-
Gaston NC-Cleveland NC-Lincoln NC-York SC-Cherokee SC-
1142 PM EDT Thu Mar 25 2021

...STRONG THUNDERSTORMS WILL IMPACT LINCOLN...CLEVELAND...GASTON...
NORTHWESTERN YORK AND NORTHEASTERN CHEROKEE COUNTIES UNTIL 1230 AM
EDT...

At 1141 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 13 miles north of Shelby to near Gaffney, and
moving east at 45 mph.

Locations to be impacted include...
Gastonia, Shelby, Gaffney, Lincolnton, Kings Mountain, Mt Holly,
Belmont, Cherryville, Bessemer City and South Gastonia.

Wind gusts up to 40 mph will be possible in these areas.

LAT...LON 3551 8096 3549 8095 3538 8097 3538 8099
      3536 8098 3532 8099 3527 8102 3522 8101
      3515 8103 3514 8105 3511 8103 3509 8106
      3504 8105 3501 8175 3553 8153 3556 8114
      3555 8096 3554 8095
TIME...MOT...LOC 0341Z 261DEG 37KT 3548 8151 3509 8167

LANE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1152 PM EDT Thu Mar 25 2021

SCZ007>009-012-013-260430-
York SC-Cherokee SC-Laurens SC-Union SC-Spartanburg SC-
1152 PM EDT Thu Mar 25 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN LAURENS...
SOUTHWESTERN YORK...SOUTHERN SPARTANBURG...SOUTHERN CHEROKEE AND
NORTHERN UNION COUNTIES UNTIL 1230 AM EDT...

At 1151 PM EDT, Doppler radar was tracking a strong thunderstorm 15
miles northwest of Laurens, or near Fountain Inn, moving northeast at
65 mph.

Locations to be impacted include...
Union, Woodruff, Pacolet, Buffalo, Jonesville, Pacolet Mills,
Lockhart, Croft State Park, Moore and Roebuck.

Wind gusts up to 40 mph will be possible in these areas.

LAT...LON 3478 8215 3511 8146 3482 8145 3482 8149
      3481 8147 3478 8145 3459 8223
TIME...MOT...LOC 0351Z 246DEG 56KT 3471 8214

LANE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1220 AM EDT Fri Mar 26 2021

SCZ008-009-012>014-260500-
York SC-Cherokee SC-Laurens SC-Union SC-Chester SC-
1220 AM EDT Fri Mar 26 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT EAST CENTRAL LAURENS...
CHESTER...YORK...SOUTHEASTERN CHEROKEE AND UNION COUNTIES UNTIL 100
AM EDT...

At 1220 AM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 9 miles west of Union to
9 miles east of Laurens, and moving east at 70 mph.

Locations to be impacted include...
Rock Hill, Union, York, Chester, Fort Mill, Tega Cay, Newport,
Lesslie, Great Falls and Monarch Mill.

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.

&&

LAT...LON 3441 8187 3485 8175 3502 8147 3508 8106
      3504 8104 3510 8093 3492 8086 3484 8087
      3483 8090 3470 8086 3464 8090 3454 8088
      3457 8142 3450 8142 3449 8148 3446 8153
      3445 8155 3448 8155 3453 8164 3443 8174
TIME...MOT...LOC 0420Z 256DEG 62KT 3477 8177 3447 8186

MOORE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1242 AM EDT Fri Mar 26 2021

GAZ010-017-NCZ062-260515-
Rabun GA-Habersham GA-Macon NC-
1242 AM EDT Fri Mar 26 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHERN HABERSHAM...RABUN AND
SOUTHEASTERN MACON COUNTIES UNTIL 115 AM EDT...

At 1241 AM EDT, Doppler radar was tracking a strong thunderstorm 10
miles north of Cleveland, or near Unicoi State Park, moving northeast
at 70 mph.

Locations to be impacted include...
Clayton, Highlands, Mountain City, Tiger, Dillard, Sky Valley,
Tallulah Falls, Lake Rabun, Lake Burton and Lakemont.

Wind gusts up to 40 mph, pea size hail 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 3482 8365 3488 8366 3492 8360 3494 8360
      3495 8355 3499 8355 3499 8349 3500 8348
      3500 8352 3516 8323 3499 8310 3488 8324
      3482 8328 3482 8331 3470 8336 3462 8364
      3466 8366 3468 8364 3476 8363 3480 8368
TIME...MOT...LOC 0441Z 240DEG 63KT 3475 8375

MOORE