Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1201 PM EDT Thu Mar 18 2021

.SYNOPSIS...
A potent low pressure system will continue to lead to showers
and thunderstorms this afternoon with a few strong to severe storms
possible. The associated cold front should track through the
forecast area during the afternoon hours. Friday the low pressure
system tracks off the East Coast into the western Atlantic. Strong
Canadian high pressure will build into the region behind the
departing low pressure system. This high pressure system will remain
over the eastern CONUS this weekend into the middle of next week
leading to drier weather.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1150 AM: Sometimes in these situations, we must wait for the
leopard to reveal his spots. That might be happening as of midday
as satellite imagery/sfc obs are showing the wedge boundary/warm
front moving northward. Meanwhile, radars show a narrow band of
showers extending from the western tip of SC down to the east
side of metro ATL. The lower Piedmont and Lakelands have broken
out ahead of this line, and the little bit of insolation in that
region should help the air mass recover across the Upstate and
toward metro Charlotte. On this trend, it is reasonable to expect
the boundary to make it north of I-85 in the early afternoon. We
still wait for the SPC mesoanalysis to respond, but the 12Z model
runs have no qualms in bringing a plume of 1500 J/kg of sfc-based
CAPE into the Charlotte metro area in the late afternoon. Will
this be enough to energize the line of convection as it moves in
from the west? Some of the CAMs think so. Bottom line...at this
point...in spite of the downgrade in risk this morning...think
it best to not give up on this one just yet. The latest guidance
theoretically has more than enough buoyancy and shear to support
a few severe thunderstorms east of the mtns, with the overall
best chance still to our east. The convective threat should end
gradually from the west this afternoon. Temps will remain tricky,
with some places in the usual spots not making it out of the 50s
while the lower Piedmont makes it well into the 70s.

Otherwise, clearing takes place behind the line of convection but
clouds will linger across the mountains and should break containment
and spread across the area during the evening and overnight. Expect
scattered to numerous showers to redevelop across the mountains,
especially along the TN border. Isolated showers will also be
possible across the I-40 corridor. Precip should mostly be rain,
but snow is possible above 5000 feet. No significant accumulations
are expected.  Lows will be 5 to 10 degrees above normal.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 200 AM Thursday: Post-frontal regime will be the main weather
headline across the entire CFWA by the start of the short-term
period. Remnants of the upper low will soon lift out of the area,
but northwest flow behind the front and a weak swath of wrap
around moisture along a baroclinic zone could spark a few showers
and enhanced cloud cover, especially along the TN border as it
sags south and east during the day Friday. As of now, precip will
remain all liquid with the exception of the highest peaks, where
temperatures could be cold enough to support snow, but little to
no accumulation is expected. NE-ly CAA will begin filtering in and
allow for the area to dry out completely by Friday evening as a
Canadian high dives south into the northeastern CONUS. Brisk NE-ly
wind at 10 to 15 kts will be in store for Saturday, while continued
cold and dry advection steadily remains in place through the rest
of the forecast period. Model guidance have hinted at developing a
coastal low just offshore the southeast coastline and a very weak
moisture fetch could spark some light precip over the Midlands of
SC Saturday night into Sunday, but should remain too far east for
any of the activity to move into our CFWA. Temperatures will be
below-normal through much of the short-term, with highs on Friday
and Saturday struggling to get out of the 40s for the mountains
and 50s elsewhere both days. Lows Friday night and Saturday night
will introduce widespread low to mid 30s in the piedmont and 20s
across the higher elevations.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 300 AM Thursday: Lingering upper trough over the southeastern
CONUS will begin to push offshore after Sunday as upper ridging
begins to move into the area from the west by the start of the
new work week. Sfc high will continue to set up shop over the
northeastern CONUS through the early part of next week. Sharp
heights falls will begin to enter the central CONUS during the same
time frame as an upper trough digs over this area under diffluent
flow that develops on the east side of the trough. Both the GFS
and ECMWF have this feature, but the timing discrepancies with
the associated cold front are evident in the latest trends. The
GFS marches the frontal boundary through the eastern CONUS and
develops some upglide activity ahead of the front with wedge-like
conditions settled in. The fropa would occur sometime on Wednesday,
with decent QPF response ahead and along the boundary and some
instability. The GFS also keeps the pattern unsettled through the
end of the extended period. On the other hand, the ECMWF introduces
a somewhat moisture starved frontal boundary and has the fropa
lagging behind by 6-12 hours compared to the GFS. The overall
forcing along the boundary is not nearly as defined as it is in the
GFS. Due to the uncertainty in model guidance this far out, I have
decided to keep just chance PoPs in the forecast during the latter
half of the medium range. Temperatures will likely run below-normal
Sunday before a rebound to near-normal values on Monday. The upward
trend will continue into Tuesday and Wednesday with above-normal
values expected due to rising heights from the upper ridging.

&&

.AVIATION /16Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Showers are moving in ahead of the convective
line to the west. Expect generally MVFR vsby and LIFR cigs even as
convection does move across the area. Have timed the line with VCTS
and TEMPO based on current movement. Vsby and cigs improve to VFR
behind the line. NE to SE wind becomes S to SW and gusty as the line
moves through. LLWS remains in place until the strong low level jet
associated with the convection clears the area. Winds turn NW and
remain gusty this evening for all but KCLT where gusts aren't
expected. MVFR cigs develop overnight at KAVL with low VFR at KCLT
and KHKY. SCT VFR at the SC sites.

Outlook: MVFR cigs continue across portions of the area Friday
with VFR Friday night into early next week.

Confidence Table...

            16-22Z        22-04Z        04-10Z        10-12Z
KCLT       High  86%     High  92%     High 100%     High 100%
KGSP       High  83%     High  97%     High 100%     High 100%
KAVL       High  86%     High  97%     Med   77%     High  86%
KHKY       High  91%     High  92%     High 100%     High 100%
KGMU       High  89%     High  97%     High 100%     High 100%
KAND       Med   75%     High  97%     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...None.
NC...None.
SC...None.

&&

SYNOPSIS...CAC
NEAR TERM...PM/RWH
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...RWH

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
448 AM EDT Thu Mar 18 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-190900-
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-
448 AM EDT Thu Mar 18 2021

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

.DAY ONE...Today and tonight.

Heavy showers and thunderstorms are likely to occur today. A few
storms may become strong to severe, producing damaging wind gusts,
hail, and an isolated tornado. The greatest threat for severe will
be along and southeast of interstate 85.

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

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
149 PM EDT Thu Mar 18 2021

NCZ508-510-SCZ007-008-181830-
Greater Rutherford NC-Eastern Polk NC-Cherokee SC-Spartanburg SC-
149 PM EDT Thu Mar 18 2021

...HEAVY RAIN SHOWERS WILL IMPACT SOUTHEASTERN RUTHERFORD...EASTERN
POLK...NORTHWESTERN SPARTANBURG AND NORTHWESTERN CHEROKEE COUNTIES
UNTIL 230 PM EDT...

At 149 PM EDT, Doppler radar indicated heavy rain showers along a
line extending from 4 miles southwest of Rutherfordton to 10 miles
southeast of Columbus, and moving northeast at 30 mph.

Locations to be impacted include...
Forest City, Rutherfordton, Spindale, Chesnee, Campobello, Ellenboro,
Bostic, Cowpens National Battlefield, Lake Bowen and Landrum.

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

LAT...LON 3532 8172 3512 8181 3509 8221 3536 8212
      3546 8170
TIME...MOT...LOC 1749Z 246DEG 28KT 3533 8203 3511 8213

LANE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
153 PM EDT Thu Mar 18 2021

SCZ005-006-010-181830-
Greater Pickens SC-Anderson SC-Greater Greenville SC-
153 PM EDT Thu Mar 18 2021

...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL GREENVILLE...NORTH
CENTRAL ANDERSON AND EAST CENTRAL PICKENS COUNTIES UNTIL 230 PM
EDT...

At 153 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles southwest of Greenville Downtown, or near Welcome, moving
northeast at 35 mph.

Locations to be impacted include...
Greenville Downtown, Easley, Greenville Eastside, West Greenville,
Mauldin, Taylors, Five Forks, Welcome, Powdersville and Cherrydale
Point.

Wind gusts up to 40 mph and dime size hail 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 3481 8261 3495 8225 3490 8222 3485 8223
      3485 8222 3483 8219 3480 8217 3481 8217
      3479 8216 3478 8215 3469 8256
TIME...MOT...LOC 1753Z 246DEG 30KT 3478 8243

LANE