Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
645 PM EDT Wed May 5 2021

.SYNOPSIS...
A cold front will continue tracking east across the forecast area
into this evening leading to the chance for showers and
thunderstorms mainly around and east of the Charlotte metro area.
High pressure fills in behind the departing front late tonight into
tomorrow leading to drier conditions and cooler temps. An upper
level trough could lead to a low chance for showers Friday mainly
for the NC mtns and NC Piedmont. High pressure returns Saturday into
most of Sunday leading to mostly conditions. A low pressure system
approaching from the west will increase shower and thunderstorm
chances late Sunday into early next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 630 PM EDT Wednesday: A decent cumulus and cirrus field
filling in over much of the CFWA. A line of showers and storms are
currently moving through the Lake Norman area and west into Lincoln
County (NC). The environment is conducive for strong convection
potential, but the rather weak cold front will limit the overall
activity and intensity. The CAMs continue to respond favorably to
the area of low-lvl convergence across the Charlotte metro area,
and develop some weak convection along the boundary as it moves
thru this evening. Shear appears to remain decent enough, i.e.,
30-35 kt, with 500-1000 J/kg of SBCAPE. Regardless, I kept the
mention of possible tsra across that area into the evening, while
a strong to severe isolated cell can't be ruled out.

Otherwise, the cold front will push its way slowly thru the CWA,
with little in the way of precip across most of the fcst area. The
front and any lingering convective activity should move SE tonight
with a quiet night otherwise. CAA from the NW filters into the CFWA
behind the fropa and provides the area with low temps dropping to
near-normal values for the beginning of May. Tomorrow will be dry
with cool high pressure spreading across the region. Lee troughing
will likely develop during the afternoon/evening hours over most
locations outside of the mountains and lead to shift in the winds to
SW-ly. Temperatures will likely run ~5-10 degrees below normal for
highs tomorrow.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 2:40 PM EDT Wednesday: Thursday night into Friday an upper
level trough with a vorticity maxima will track east across the
forecast area to kick off the short term period. This trough will
allow rain chances to enter back into the forecast with NC seeing
the best chance for showers, while SC stays mostly dry. Low to mid-
level moisture looks to be lacking with this system, so any QPF
should be fairly light. Cloud cover will also increase in response
to this shortwave. Friday low RH values ranging from the upper 20s
to low 30s are expected outside of the NC mtns. These low RH values
combined with breezy NW winds ranging from 10 to 15 mph could lead
to fire wx concerns, especially across SC. Depending on how much
moisture is present with the shortwave, the Piedmont of NC could
also have fire wx concerns present. Friday has the potential to be
the coolest day of the week with highs only getting into the 50s and
60s in the mtns, (with higher elevations potentially only seeing
highs in the 40s), and mid 60s to low 70s outside the mtns. These
temps would put us well below normal for May.

Friday night could be the coolest night of the week with lows
dropping into the upper 30s and mid 40s across much of the forecast
area. Some higher elevations could see lows in the mid 30s.
Confidence is low on frost development Friday night into early
Saturday morning at this time due to the fact that a slight breeze
will remain in place across the mtns as well as a limited amount of
moisture available due to high pressure over the area. Saturday high
pressure remains over much of the region leading to drier
conditions. Rain showers are possible Saturday afternoon and evening
across the NC/TN border thanks to an approaching low pressure system
out of the west.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 110 PM Wed: A fast quasi-zonal flow still looks to evolve
from early Sunday into Monday. This comes as shortwaves rotate
through a longwave trough over eastern Canada. In response the
OH Valley warm front will shift north as heights rise over the
mid-Atlantic on Sunday. As the next shortwave digs into the Great
Lakes region, weak cyclogenesis will occur over the western portion
of that front. As this system moves east, a cold front will push
south thru the TN Valley and across the southern Appalachians. The
approach of the front will bring slowly increasing PoPs from the
NW thru Monday. Some of the guidance indicates favorable timing for
convection ahead of the front Monday afternoon, but the orientation
of the front and modest instability/shear do not suggest appreciable
severe risk.

The current slate of deterministic models takes the front past the
CWA by Tue morning, but diverge from there. The general expectation
is that the next trough will pick up the stalled front as it emerges
from the lower MS Valley; the 00z Euro and Canadian suggest this
will happen as soon as Tuesday night, ramping PoPs back up by that
time. Most of the GEFS members keep us dry thru Wednesday, and
the operational GFS even later (but with a much stronger trough).

Temps will remain a little below normal for mins Sunday morning,
but should be held up a few degrees Monday morning on account of
cloud cover. Sun-Mon maxes will be near normal, but cooler Tuesday
assuming the front clears the area.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Expect VFR conditions to prevail through the
TAF period. Dry air has been filtering into the region behind the
cold front with winds shifting to the NW. Winds should remain SWLY
to WLY with enough mixing to allow for occasional gusts ahead of the
front, but the fropa should occur around 00Z or a little after at
all terminals. As the cold front moves thru the region this
aftn/evening, guidance continues to generate some scattered showers
and possibly a few weak thunderstorms over the western Piedmont.
This is the case currently with activity picking up along the
boundary just N & E of KCLT. This could slide a -RA or potentially a
-TSRA, but confidence is low for a TEMPO group with a TS mention, so
decided to back off and go for -RA through 00Z for KCLT. Expecting
the rest of the terminals to remain dry, especially at KAVL and KHKY
where the cold front has already passed. Conditions should calm
overnight as sfc high builds in from the west with mostly clear
skies expected tonight. Some potential for fog to develop over the
French Broad Valley, but should stay W of KAVL. Dry tomorrow with
lee troughing expected to shift winds to a SW-ly direction tomorrow
afternoon/evening at all locations except for KAVL. Low-end gusts
will be in store tomorrow as well with good mixing at the low-
levels. The best chance for gusts will likely be at KAVL due to the
gap wind that develops with NW-ly flow at the sfc.

Outlook: Predominately VFR conditions are expected Thursday thru
the weekend. The next system to bring restrictions is looking like
it will arrive on Monday of next week.

Confidence Table...

            22-04Z        04-10Z        10-16Z        16-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  95%     High  87%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     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...AP
NEAR TERM...CAC/JPT
SHORT TERM...AP
LONG TERM...Wimberley
AVIATION...CAC

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
544 AM EDT Wed May 5 2021

GAZ010-017-018-026-028-029-NCZ033-035-048>053-058-059-062>065-
501>510-SCZ001>007-010>013-019-060945-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-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-Spartanburg-Anderson-Abbeville-
Laurens-Union SC-Greenwood-
544 AM EDT Wed May 5 2021

This Hazardous Weather Outlook is for northeast Georgia, the
mountains and foothills of North Carolina, upstate South Carolina.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ036-037-056-057-068>072-082-SCZ008-009-014-060945-
Iredell-Davie-Catawba-Rowan-Cleveland-Lincoln-Gaston-Mecklenburg-
Cabarrus-Union NC-Cherokee-York-Chester-
544 AM EDT Wed May 5 2021

This Hazardous Weather Outlook is for the western Piedmont of North
Carolina and northern upstate of South Carolina, including the
Charlotte metro area.

.DAY ONE...Today and tonight.

A few thunderstorms may develop along a cold front this afternoon,
with gusty winds, small hail, brief heavy downpours, and cloud-to-
ground lightning the main threats. There is a small possibility that
one of the storms, if they develop, could produce brief severe
weather in the form of large hail and damaging winds. The storms
should move off to the southeast by early evening as the front
passes.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

PM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
546 PM EDT Wed May 5 2021

NCZ036-056-057-069>072-052230-
Rowan NC-Gaston NC-Iredell NC-Lincoln NC-Cabarrus NC-Mecklenburg NC-
Catawba NC-
546 PM EDT Wed May 5 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT NORTHERN CABARRUS...
SOUTHEASTERN CATAWBA...LINCOLN...SOUTHEASTERN IREDELL...NORTHWESTERN
MECKLENBURG...SOUTHERN ROWAN AND NORTHERN GASTON COUNTIES UNTIL 630
PM EDT...

At 545 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 12 miles north of
Huntersville to 5 miles west of Lincolnton, and moving east at 25
mph.

Locations to be impacted include...
Huntersville, Kannapolis, Lincolnton, Downtown Concord, Cornelius,
Mooresville, Davidson, Cherryville, China Grove and Maiden.

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...

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.

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.

&&

LAT...LON 3551 8019 3550 8024 3550 8029 3549 8030
      3531 8134 3552 8151 3566 8076
TIME...MOT...LOC 2145Z 286DEG 21KT 3559 8084 3550 8134

JMP

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
632 PM EDT Wed May 5 2021

NCZ036-057-071-072-052300-
Rowan NC-Iredell NC-Cabarrus NC-Mecklenburg NC-
632 PM EDT Wed May 5 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT NORTHERN CABARRUS...
SOUTHEASTERN IREDELL...NORTHWESTERN MECKLENBURG AND ROWAN COUNTIES
UNTIL 700 PM EDT...

At 631 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 7 miles north of
Salisbury to 4 miles north of Huntersville, and moving east at 45
mph.

Locations to be impacted include...
Huntersville, Kannapolis, Downtown Concord, Salisbury, West Concord,
Cornelius, Davidson, China Grove, Spencer and Landis.

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.

LAT...LON 3550 8029 3545 8033 3534 8097 3536 8092
      3537 8095 3555 8082 3578 8052 3578 8048
      3574 8046 3572 8042 3572 8034 3571 8032
      3568 8033 3563 8029 3562 8025 3558 8021
      3555 8021 3551 8018
TIME...MOT...LOC 2231Z 256DEG 41KT 3577 8044 3547 8083

JMP

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
809 PM EDT Wed May 5 2021

NCZ071-072-082-060045-
Union NC-Cabarrus NC-Mecklenburg NC-
809 PM EDT Wed May 5 2021

...AN AREA OF HEAVY RAIN WILL IMPACT SOUTH CENTRAL CABARRUS...
SOUTHEASTERN MECKLENBURG AND NORTHERN UNION COUNTIES UNTIL 845 PM
EDT...

At 807 PM EDT, Doppler radar indicated the leading edge of an area of
heavy rain along a line extending from 9 miles southwest of
Albemarle to 5 miles southeast of Uptown Charlotte, and moving east
at 25 mph.  Some lightning may develop as these showers move
southeast.

Locations to be impacted include...
Monroe, South Charlotte, Matthews, Mint Hill, Indian Trail,
Weddington, Stallings, Unionville, Wesley Chapel and Lake Park.

Very heavy rainfall rates up to 2 inches per hour will be possible in
these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

&&

LAT...LON 3505 8029 3496 8071 3515 8084 3527 8045
      3519 8051 3518 8050 3518 8048 3517 8047
      3516 8044 3517 8042 3516 8041 3518 8037
      3517 8036 3518 8031 3519 8030 3519 8028
TIME...MOT...LOC 0007Z 292DEG 21KT 3526 8031 3517 8077

JMP