Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
240 PM EDT Wed Jul 14 2021

.SYNOPSIS...
The Bermuda high will begin breaking down this weekend with weak
troughing possibly setting up over the region early next week. This
pattern shift will likely support an increase in mainly afternoon to
evening showers and thunderstorms and a gradual cooling trend.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 220 PM: An inland extension of the Bermuda High will be
the dominant feature in our weather pattern through Thursday. A
seasonably moist airmass with elevated PWATs and mediocre lapse
rates will accompany the subtropical airmass. PoPs will remain
diurnally driven and the main impact will be locally heavy rainfall,
with low DCAPE due to all the moisture. A damaging microburst
wouldn't be out of the question given the season, but the rainfall
rates by and large will outweigh the wind risk.

As noted by previous forecaster, a little kink in mid-upper
height contours will linger across the southern Appalachians
this afternoon; this is an extension of the trough crossing
eastern Canada and the NE CONUS. 500mb progs depict some weak
vorticity therein, and some degree of midlevel convergence is also
depicted. Convection that fired near the Blue Ridge Escarpment
appears to have been kicked off with the aid of this feature. It is
progged to shift into the Piedmont as it dampens out this evening,
with the parent trough scooting off toward the Atlantic. NAMNest
currently appears to have had the best handle on convection so
far today; it depicts cells propagating east in response to the
movement of the trough. Slightly above-climo PoPs largely reflect
CAM consensus. By Thursday the kink feature should have been
absorbed into the pattern. We are left with the diurnal instability
as our only forcing mechanism aside from the usual mechanical lift
in weak SW flow. PoPs thus will drop back a bit, more or less in
line with climatology. Temps will be near or slightly above climo.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 100 PM Wednesday: Slight height falls will be in store during
the short term as the overall synoptic pattern begins to change
over portions of the eastern CONUS. The Subtropical High just of
the Southeast coast will become somewhat suppressed in response to
a low-amplitude trough that is expected to dig through the Midwest
and Upper Great Lakes region late Thursday and into the OH Valley
by Friday. Embedded shortwaves with provide upper-level support
for convective development, while the Bermuda High continues to
pump in a moist southwesterly flow through much of the forecast
period. The convective coverage should be a category over scattered
on Friday as steeper mid-level lapse rates and better instability
settle over the CFWA. Strong to severe storms could develop, but
the threat is limited, but any training cells or periods of heavy
rainfall will be conducive to a localized hydro concern. Deep
layer southwesterly flow and persistent embedded shortwaves will
keep shower and thunderstorm chances lingering into Friday night,
especially in the favorable slopes in southwest mountains of NC.

The Subtropical High will try to hold strong going into the weekend,
which sandwiches the CFWA between a typical summertime regime and
added upper level support with the aforementioned trough lingering
to the northwest. The Bermuda High will continue to produce moisture
advection from the southwest as lee troughing sets up shop over
the Carolina piedmont/foothills and thus, an uptick in PoPs and
convective coverage will return to the forecast yet again on
Saturday, especially during the afternoon/evening hours. Hot and
humid conditions are expected to continue as temperatures remain
at or slightly above normal through the short term.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 215 PM Wednesday: Model guidance are slowly coming to a
consensus on the overall pattern going into the weekend and the
early part of next week. Upper troughing will continue to linger
over the eastern CONUS during a portion of the extended as a strong,
broad ridge builds over the Four Corners region and Rockies. An
attendant cold front is shown riding underneath the trough, but
the timing of a potential passage is still uncertain as the global
models push the boundary through the CFWA late Monday into early
Tuesday. This will bring unsettled weather Sunday and Monday with a
defined lifting mechanism and persistent moisture advection from the
Bermuda High. The summertime regime will also be conducive for good
instability, but slightly higher shear parameters and additional
upper-level support from embedded shortwaves will prog a potential
severe and hydro threat Sunday and Monday. With a possible fropa
on Tuesday, drier conditions could prevail through the latter half
of the period. A post frontal regime would prevail if there was a
clean fropa Tuesday, which would allow for very comfortable weather,
especially for mid-July standards. This will all be dependent on
the location of the frontal boundary as model guidance keeps the
front stalled south of the CFWA, but full fropa's are not typical
in July and thus, kept at least diurnal PoPs in the forecast
through Day 7. The hydro threat could become better enforced if
the frontal boundary stalls in or near the CFWA by the first half
of next week. A lot more questions than answers at the moment, but
the one thing that is for certain is that we will be in an unsettled
pattern through at least Monday. Temperatures will be at or slightly
below normal on Sunday, but lower heights, enhanced cloud cover,
and increased rain chances will bring highs to below normal values
during the start of the new work week. Low temperatures will remain
at or slightly above normal through much of the medium range.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
At KCLT and Elsewhere: A generally typical summertime pattern will
persist through Thursday, although convective coverage will be
somewhat enhanced this aftn by a weak trough axis drifting across
the area. Ongoing SHRA/TSRA over the NC mountains will propagate
eastward thru early evening with the aid of the trough. Convection
looks less likely at KGSP/KGMU but still warranted a low-end
TEMPO. KAND is the only site where mention was brought down to
VCSH. Some restrictions may develop near daybreak in areas where
heavy rain falls this aftn from TSRA, but confidence too low to
reflect that. Did include valley fog/stratus mention at KAVL in
the morning. Somewhat lower convective chances Thu aftn following
dissipation of trough; with lower PoP and confidence, no PROB30
yet included for Thu even at KCLT. Winds mainly light SW, except
KAVL where more variation is expected due to valley effects.

Outlook: An unsettled pattern, with afternoon/evening storms and
morning fog/stratus restrictions, will persist for several more
days at least. A front near the region this weekend may enhance
afternoon convective coverage.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     Med   78%
KGSP       High 100%     High 100%     High 100%     Med   78%
KAVL       Med   66%     High  95%     Med   66%     Med   60%
KHKY       High 100%     High 100%     High 100%     Med   78%
KGMU       High 100%     High 100%     High 100%     Med   78%
KAND       High 100%     High 100%     High 100%     Med   78%

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...Munroe
NEAR TERM...Wimberley
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...Wimberley

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
338 PM EDT Wed Jul 14 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-151945-
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-
338 PM EDT Wed Jul 14 2021

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

.DAY ONE...This afternoon and tonight.

Scattered thunderstorms are expected to continue across the forecast
area this afternoon and into the early evening. Coverage and
intensity should remain greatest over the mountains and foothills,
but at least scattered thunder is expected across the western
Piedmont and Upstate as well. Frequent cloud- to- ground lightning
strikes are likely, along with heavy downpours, which could result in
localized flooding in areas with poor drainage or where storms
linger. As usual, cannot rule out a few stray severe storms. In any
case, thunder activity should steadily diminish after sunset.

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

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

MPR

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
412 PM EDT Wed Jul 14 2021

NCZ037-142045-
Davie NC-
412 PM EDT Wed Jul 14 2021

...A STRONG THUNDERSTORM WILL IMPACT DAVIE COUNTY UNTIL 445 PM EDT...

At 412 PM EDT, Doppler radar was tracking a strong thunderstorm near
Mocksville, moving northeast at 30 mph.

Locations to be impacted include...
Mocksville, Bermuda Run, Cooleemee, Fork Church, Advance and
Farmington.

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 3589 8041 3588 8042 3587 8039 3584 8048
      3581 8056 3583 8060 3582 8061 3584 8063
      3594 8067 3605 8051 3604 8049 3606 8046
      3603 8044 3601 8042 3599 8042 3596 8038
      3589 8037
TIME...MOT...LOC 2012Z 237DEG 27KT 3591 8054

KRENTZ