Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
150 PM EDT Mon Jul 26 2021

.SYNOPSIS...
A weak cold front will move south across our area tonight and
Tuesday.  This will result in scattered to numerous showers and
thunderstorms with a few locations getting excessive rainfall in a
short time.  Expect drier and hotter conditions Wednesday through
Friday with high temperatures feeling like 100 degrees in the
piedmont.  A weak cold front will drop south this weekend cooling
temperatures to near normal.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1035 am: The region is already becoming unstable this
morning, with a small amount of vertical shear growing in the
convective layer. Upper heights will fall slightly across the
entire Southeast through the near term, as a series of speed maxima
pass through the Mid-Atlantic and northeast. An associated weak
cold frontal zone will sag into our North Carolina zones by the
end of the day, and this will act upon a moderately unstable air
mass to focus scattered to numerous convective coverage...first
across the mountains and I-40 corridor by the early-afternoon,
progressing to the I-85 corridor during mid- to late-afternoon and
early evening. PoPs are advertised in the 60-70% range in this area
prior to 00Z Tuesday.  With the faster mid-level flow expected to
remain north of the forecast area, wind shear will remain weak,
but the degree of instability (SBCAPE in excess of 2500 J/kg in
many areas) combined with the volume of storms will likely yield a
handful of pulse severe storms. Meanwhile, forecast wind profiles
remain supportive of slow-moving and back-building cells. With
warm cloud depths forecast to be AOA 11 kft through the period,
there is expected to be a bit of an uptick in the potential for
locally excessive rainfall/flash flooding, warranting the upgrade to
a slight risk in WPC's Excessive Rainfall Outlook...mainly across
western NC, with the latest Outlook encompassing the rest of the
CWA in a marginal risk.

Convective coverage is expected to diminish this evening, but with
the weak boundary remaining in the area and conditions remaining
very moist...with moderate instability likely persisting...some
degree of isolated/scattered coverage will likely continue through
the overnight, with a diminishing, albeit non-zero threat for
localized flash flooding continuing. Temps will be a couple of
degrees above normal through the period.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 300 AM EDT Monday: No major changes to the overall synoptic
pattern. The ridge of high pressure will continue to dominate across
the western and central CONUS while a trough digs south across the
New England and the Mid-Atlantic states. The southeastern periphery
of this ridge out west is still expected to gradually nudge eastward
Wednesday into Wednesday night.

At the sfc, the cold front associated with the upper-level trough
should be draped across the southern and eastern tier of the CWA
early Tuesday. This allows moisture to linger across the western
Carolinas and northeast Georgia with PWATs ranging from 1.50 to 1.90
inches across the mountains and 1.90 to 2.50 inches across the North
Carolina Foothills and Piedmont, and the South Carolina Upstate.
These PWAT values combined with efficient warm cloud processes will
lead to the potential for isolated flooding or flash flooding again
on Tuesday. Areas that received heavy rainfall the last few days as
well as locations that repeatedly receive heavy downpours are the
most susceptible. WPC currently has the entire CWA in a marginal
risk on Tuesday for excessive rainfall. PoPs will increase
throughout the day becoming likely by Tuesday afternoon and evening
with widespread showers and thunderstorms tracking across the CWA.
Although the potential for flooding or flash flooding looks to be
the main concern with this frontal boundary, there is some potential
for isolated severe wx as instability will be present. GFS model
soundings show SBCAPE values ranging from 1000 to 1500 J/kg across
the mountains and NC Piedmont and 1500 to 2000 J/kg across the SC
Upstate. The Canadian and ECMWF seem to be in agreement with these
SBCAPE values. However, NAM model soundings are on the higher end
with SBCAPE values ranging from 1500 to 2000 J/kg across the
mountains and NC Piedmont and 2500+ J/kg across the SC Upstate. All
global models are in good agreement that the 0-6 km bulk shear
should range from 15 to 25 kts. Therefore, cannot rule out isolated
strong to severe storms Tuesday with the main potential impact being
isolated damaging wind gusts. SPC keeps the entire area in a general
thunderstorm risk for Tuesday. The cold front should weaken and
eventually dissipate late Tuesday allowing PWATs to gradually
decrease across the CWA late Tuesday night into early Wednesday. As
a result, shower and thunderstorms should gradually taper off from
west to east Tuesday evening into Wednesday morning. Tuesday's highs
should be slightly cooler compared to Monday thanks to northerly
flow behind the FROPA.

Wednesday should be dry as the ridge of  high pressure nudges
westward into the Southeastern CONUS. Kept a slight chance for
isolated showers and thunderstorms for the extreme southeastern
zones as the GFS and ECMWF were hinting at activity in that
vicinity. Confidence on this occurring is very low as the extension
of the ridge of high pressure should lead to subsidence across the
region. Otherwise, Wednesday will be noticeably hotter compared to
Tuesday thanks to the SW periphery of the ridge over the area. Heat
indices could reach the triple digits across the extreme southern
tier of the SC Upstate and NE GA.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 AM EDT Monday: The overall synoptic pattern remains the
same into late this week with troughing across the Northeastern
United States and a ridge across the central and western US. Late
this weekend into early next week this high pressure ridge should
gradually breakdown across the western US, building across the
southern US while troughing remains over much of the Northeast.

The ridge of high pressure across much of the CONUS will continue to
extend across the CWA Thursday before retreating west Friday. This
will lead to continued dry and hot conditions Thursday. Heat indices
could reach the triple digits again on Thursday and Friday. This
looks most likely across the far southern and southeastern zones.

A cold front drops out of the OH Valley Thursday tracking into the
CWA Friday into Saturday leading to increased shower and
thunderstorm chances. This front has the potential to stall across
the area Sunday. Forecast confidence remains low at this time due to
model disagreement on the timing and placement of the QPF.
Therefore, have kept only a slight chance to chance for PoPs this
weekend. Early next week another cold front looks to drop out of the
OH valley tracking into NE GA and the western Carolinas brining yet
another chance for showers and thunderstorm. Capped PoPs at chance
for now due to model disagreement as well as this FROPA occurring
towards the end of the extended forecast period. High temps should
be noticeably cooler this weekend into early next week compared to
Thursday and Friday.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: All TAF sites are VFR at this time.
Scattered clouds are increasing in coverage across the region
as a cold front approaches from the northwest.  This front has
already begun to spin up a line of showers and thunderstorms
over the northern foothills, and should continue to produce such
activity throughout the afternoon and evening.  All TAF sites
carry at least chance TSRA and vicinity thunder from 19Z until 00Z.
The most intense convection should diminish past this point in time,
though scattered showers should persist for several more hours into
the night.  There is increased confidence in the development of
IFR restrictions at KHKY, and LIFR restrictions at KAVL owing to
the development of fog/low stratus in the hours before sunrise.
All other sites remain VFR/MVFR into the morning.  We should
see scattered showers and storms tomorrow afternoon again, but
confidence is low enough on the timing and coverage to simply
carry VCSH and a few PROB30s.

Outlook: With the frontal boundary gradually becoming more diffuse
past Tuesday evening, drier air filters into the area and results in
a lull in activity Wednesday and Thursday.  Diurnally-drive pulse
thunderstorms should pick up again on Friday, along with a chance
for fog and low stratus Friday and Saturday morning.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High 100%     High  83%
KGSP       High 100%     High 100%     High  83%     Low   56%
KAVL       High 100%     High 100%     High  83%     High  90%
KHKY       High 100%     High 100%     Med   66%     High  90%
KGMU       High 100%     High 100%     High  83%     Med   66%
KAND       High 100%     High 100%     High 100%     Med   66%

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

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
405 AM EDT Mon Jul 26 2021

NCZ036-037-057-270815-
Iredell-Davie-Rowan-
405 AM EDT Mon Jul 26 2021

This Hazardous Weather Outlook is for piedmont North Carolina.

.DAY ONE...Today and tonight.

A backdoor cold front will allow for shower and thunderstorm
development this afternoon into this evening. The main hazards are
cloud- to-ground lighting, isolated strong to severe storms bringing
the potential for damaging wind gusts, and heavy downpours. Any
areas that repeatedly see heavy downpours could experience excessive
rainfall leading to the potential for isolated flooding or flash
flooding.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-028-029-NCZ033-035-048>053-056-058-059-062>065-
068>072-082-501>510-SCZ001>014-019-270815-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-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-
405 AM EDT Mon Jul 26 2021

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

.DAY ONE...Today and tonight.

A backdoor cold front will allow for shower and thunderstorm
development this afternoon into this evening. The main hazards are
cloud- to-ground lighting and heavy downpours. Any areas that
repeatedly see heavy downpours could experience excessive rainfall
leading to the potential for isolated flooding or flash flooding.
Isolated strong to severe thunderstorms cannot be ruled out. The main
potential impact from any strong to severe storm would be isolated
damaging wind gusts.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
939 AM EDT MON JUL 26 2021

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

0830 PM     FLASH FLOOD      1 SSE CULLOWHEE         35.29N 83.17W
07/25/2021                   JACKSON            NC   911 CALL CENTER

            WEST ROGERS ROAD WAS WASHED OUT AND COMTINUES TO BE
            CLOSED TODAY AS REPAIR WORK IS BEING DONE WITH EXPECTED
            REOPENING LATE TODAY. NEARBY LEDBETTER ROAD WAS CLOSED
            TEMPORARILY SUNDAY EVENING DUE TO A TREE THAT FELL ACROSS
            THE ROADWAY WHERE THE ROOTS MAY HAVE BEEN WASHED OUT
            CAUSING THE TREE TO FALL.

&&

OUTLAW

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
122 PM EDT Mon Jul 26 2021

NCZ033-050-501>507-261745-
McDowell Mountains NC-Caldwell Mountains NC-Burke Mountains NC-
Greater Burke NC-Greater Caldwell NC-Eastern McDowell NC-
Rutherford Mountains NC-Avery NC-Mitchell NC-
122 PM EDT Mon Jul 26 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT MCDOWELL...SOUTHEASTERN
MITCHELL...CALDWELL...SOUTHEASTERN AVERY AND WESTERN BURKE COUNTIES
UNTIL 145 PM EDT...

At 121 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 10 miles south of Deep
Gap to 16 miles southwest of Marion, and moving southeast at 15 mph.

Locations to be impacted include...
Lenoir, Marion, Morganton, Gamewell, Glen Alpine, Old Fort, Cedar
Rock, Linville Falls, B.R. Parkway-Craggy To Little Switzerland and
Lake James State Park.

Wind gusts up to 35 mph 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 3612 8155 3607 8141 3604 8139 3602 8134
      3600 8133 3555 8200 3554 8208 3547 8213
      3553 8218 3553 8217 3560 8228 3562 8227
      3568 8229 3574 8219 3579 8216 3611 8179
TIME...MOT...LOC 1721Z 325DEG 12KT 3608 8147 3555 8225

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
145 PM EDT Mon Jul 26 2021

NCZ035-501>506-261830-
McDowell Mountains NC-Caldwell Mountains NC-Burke Mountains NC-
Greater Burke NC-Greater Caldwell NC-Alexander NC-
Eastern McDowell NC-
145 PM EDT Mon Jul 26 2021

...STRONG THUNDERSTORMS WILL IMPACT NORTHEASTERN MCDOWELL...NORTHERN
ALEXANDER...CALDWELL AND BURKE COUNTIES UNTIL 230 PM EDT...

At 145 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 9 miles northeast of Lenoir to 8 miles west of
Morganton, and moving southeast at 15 mph.

Locations to be impacted include...
Lenoir, Morganton, Marion, Sawmills, Granite Falls, Valdese,
Gamewell, Hudson, Cajah's Mountain and Drexel.

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.

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 3607 8141 3604 8140 3602 8135 3600 8133
      3603 8127 3604 8120 3603 8117 3604 8113
      3603 8107 3605 8103 3602 8102 3558 8181
      3558 8182 3556 8184 3579 8211 3610 8152
TIME...MOT...LOC 1745Z 303DEG 11KT 3598 8139 3574 8185

ARK

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
222 PM EDT Mon Jul 26 2021

NCZ035-036-056-502-261845-
Iredell NC-Greater Caldwell NC-Alexander NC-Catawba NC-
222 PM EDT Mon Jul 26 2021

...STRONG THUNDERSTORMS WILL IMPACT NORTH CENTRAL CATAWBA...
ALEXANDER...NORTHERN IREDELL AND SOUTHEASTERN CALDWELL COUNTIES UNTIL
245 PM EDT...

At 221 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 9 miles south of Jonesville to 11 miles east of
Taylorsville to 6 miles north of Hickory, and moving southeast at 10
mph.

Locations to be impacted include...
Taylorsville, Hickory, Sawmills, Granite Falls, Bethlehem, Hudson,
Stony Point, Harmony, Love Valley and Lake Hickory.

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.

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 8069 3598 8070 3590 8079 3575 8137
      3577 8137 3576 8140 3585 8153 3605 8101
TIME...MOT...LOC 1821Z 295DEG 9KT 3610 8083 3597 8098 3584 8133

ARK