Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1140 AM EDT Sun Aug 12 2018

.SYNOPSIS...
A low level boundary will remain stalled across the Piedmont and aide
in developing afternoon showers and thunderstorms which will
linger into the evening. An upper-level disturbance will track
northeast the region late Monday leading to drier weather Tuesday
and Wednesday. Moisture levels increase Thursday through the end of
the week ahead of an approaching cold front.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1130 AM...The forecast looks on track per latest trends. The
13z Day 1 Convective Outlook from SPC has expanded the marginal risk
for severe wx a bit west into our NW Piedmont and the Charlotte
area. This makes sense given good agreement among the CAMs on
convection firing across the Blue Ridge escarpment then drifting
east across the NC Piedmont this aftn. Freezing levels have dropped
1000 ft from yesterday on the GSO sounding. Effective shear is
forecast to be around 25-30 kts with MUCAPE arond 3000 J/kg in the
risk area. So a few strong to severe storms will be possible.
Further west, the threat looks lower, but scattered storms still
expected. Temps will top out around normal with humid conditions.

Previous Discussion... A strong ulvl low will pivot over the area
and pockets of h5 vort energy along with broad lift will increase
thru the afternoon and linger into the evening hrs. Soundings show
muCAPE values reaching moderate levels while a relative uptick in
bulk shear commences. Overall shear will remain fairly low...yet
enuf will be present to allow for multi-cell tstms capable of
producing organized cold pools. Thus...will anticipate tstms
developing across the higher terrain by mid afternoon and
propagating line progressing east across the fthills/piedmont
regions late afternoon into the evening. Freezing levels will remain
quite high...but a rather dry sub/cloud layer with weak flow will
allow for efficient evap cooling and moderate dCAPE leading to
strong/severe downdrafts and outflows with any of these storms.
Large hail will also be a possibility with modest accelerations thru
the HGZ and a deeply destabilized atmos thru 200 mb (EL). Max temps
will range from the L80s across the mtn valleys to U80s non/mtns.
Lows will hover right arnd normal levels.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 215 AM EDT Sunday: The trough axis associated with the upper
low over the Upper OH Valley will cross the area Monday. At the
surface, the weak boundary in the lee trough position moves east as
well. However, there will be some lingering moisture, instability,
and forcing especially across the I-77 corridor. Therefore, will
keep chance PoP limited to that area with slight chance PoP
elsewhere. Diurnal timing continues to be favored.

Short wave ridging and a much drier air mass build in on Tuesday
behind the departing upper low and surface boundary. This finally
brings an end to the instability and active convection that have
been a daily occurrence.

Temps will be near normal Monday and slightly above normal for
Tuesday.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 325 AM EDT Sunday: Short wave ridging over the area Wednesday
moves east on Thursday as a series of short waves move into the
Midwest. These short waves rotate toward the area Friday and
Saturday. The Thursday short wave is dampened by South Atlantic
upper ridging building west into the SE CONUS. The ridge weakens
Friday allowing the next short waves to dig toward the area. The
guidance then disagrees on the timing of the next short wave for
Saturday with the GFS slower than the ECMWF.

At the surface, dry high pressure over the area moves begins to move
east on Wednesday. There may be enough moisture return across the
mountains for instability and diurnal convection. Moisture return
then strengthens Thursday and Friday for a resultant increase in
instability and diurnal convection coverage. With the slower
movement on the GFS, it has lower diurnal convective coverage than
the faster ECMWF. Have gone with a model blend for PoP given the
differences. All this means PoP trends favor the mountains each day.
Chance PoP over the mountains and slight chance elsewhere Thursday
with chance PoP all areas Friday and Saturday.

Temps increase to above normal Wednesday and Thursday then drop to
near or just below normal for Friday and Saturday.

&&

.AVIATION /16Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Continued low VSBY and CIGs this morning into
the MVFR/IFR range mainly across locales which received rainfall
during the previous 24 hrs. Expect flight restrictions to return to
VFR aft 13z/14z all terminals with SCT Cu developing by midday. The
afternoon convection still looks possible late across most sites as
large-scale ulvl forcing combines with a destabilizing atmos and a
line of multicell storms is possible. There will be low-end shear to
aide in some organization...so tstms may continue later into the TAF
period across the non/mtn sites.

Outlook: Expect aftn/evening isolated to scattered showers and
thunderstorms Monday mainly across the higher terrain with periods
of MVFR/IFR possible due to low cigs and heavy downpours. Morning
restrictions due to areas of fog/low cigs will also be possible each
day, especially in mountain valleys. Drier weather is expected for
Tuesday and Wednesday, but will be followed by a return of diurnal
convection on Thursday.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High  94%
KAVL       High 100%     High 100%     High  86%     Med   78%
KHKY       High 100%     High 100%     High 100%     Med   77%
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 and ensemble forecasts
are available at the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

SYNOPSIS...SBK
NEAR TERM...ARK/SBK
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...SBK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
430 AM EDT Sun Aug 12 2018

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-130830-
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-
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-Chester-Greenwood-
430 AM EDT Sun Aug 12 2018

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

.DAY ONE...Today and tonight.

Scattered to numerous thunderstorms are expected to develop this
afternoon and evening. A few of these storms could become severe with
damaging wind gusts. Isolated flooding will also be possible. Any
storm will be capable of producing strong wind gusts, heavy rainfall,
and cloud to ground lightning.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to forward any reports of large hail,
damaging winds, tornadoes, or flash flooding to our office.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1250 PM EDT SUN AUG 12 2018

NCZ501-502-121730-
Caldwell Mountains NC-Greater Caldwell NC-
1250 PM EDT SUN AUG 12 2018

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN CALDWELL COUNTY
UNTIL 130 PM EDT...

At 1250 PM EDT, Doppler radar was tracking a strong thunderstorm near
Blowing Rock, or near Blowing Rock In Caldwell County, moving east at
10 mph.

Locations to be impacted include...
Blowing Rock In Caldwell County, Patterson and Upton.

Nickel size hail will be possible in these areas.

LAT...LON 3612 8155 3610 8152 3610 8150 3609 8147
      3609 8145 3607 8144 3608 8142 3607 8142
      3592 8148 3608 8174 3612 8173
TIME...MOT...LOC 1650Z 287DEG 8KT 3610 8166

WJM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
221 PM EDT SUN AUG 12 2018

GAZ017-121845-
Habersham GA-
221 PM EDT SUN AUG 12 2018

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN HABERSHAM COUNTY
UNTIL 245 PM EDT...

At 220 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles south of Clarkesville, or near Cornelia, moving east at 20 mph.

Locations to be impacted include...
Clarkesville, Cornelia, Baldwin, Demorest, Mount Airy, Alto and
Raoul.

Pea size hail will be possible in these areas.

LAT...LON 3454 8362 3457 8363 3463 8346 3449 8346
      3448 8348 3449 8354 3446 8358 3445 8359
      3445 8360 3443 8362 3451 8367
TIME...MOT...LOC 1820Z 258DEG 26KT 3453 8354

WJM