Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
504 PM EDT Mon Aug 7 2017

.SYNOPSIS...
A warm front will remain north of the area tonight as low pressure
moves from Tennessee to Virginia. The low pressure will move off
the New England Coast and pull the front back south over the forecast
area as a cold front tomorrow. The front is expected to stall
again across our region and remain through the end of the week,
with deep moisture and periods of heavy rain likely.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 500 PM EDT Monday:  Sct/num showers and thunderstorms
will continue to sweep northward across northeast GA and the
western Carolinas through the evening, with thunder becoming less
likely into/through the overnight hours.  Pop will remain elevated
regionwide as a result, with the highest pops remaining across the
high terrain where likely/cat levels are favored, tapering to high
chance to low likely levels southeastward across the Piedmont.
As for threats, a few of these stronger cells could produce
gusty winds this afternoon, however the primary threat will be
for localized heavy rainfall given training and Pwats in excess
of 2 inches.

As of 230 PM: Muggy, unsettled weather conditions expected thru the
Near Term, as a cold front approaches from the north. A positively
tilted upper trough will dig over the Ohio Valley tonight, while
a sfc low pressure wave tracks across the Central Appalachians.
Forecast soundings show very moist air mass in place, with low LFC
heights and high freezing levels. Bulk shear is weakening and upper
forcing with the upper trough doesn't look strong enough to make for
real robust updrafts, as SBCAPE is only around 1500 J/kg. Where CAPE
is a little higher over the Midlands and Low Country, there are a
few strong storms. So I think severe threat is fairly low. The main
threat tonight into Tuesday will be locally heavy rain. But even
with this, I don't think things should get too out of hand. Will
continue to mention heavy rain in the HWO, given the very moist
air mass, and possibly some training convection. The highest QPF
is expected to be in the western NC mountains, where WSW upslope
flow helps enhance amounts of 1-2". The rest of the area should
see generally 0.5 to 0.75" amounts.

Overnight, convection should generally wane, but guidance does show
additional precip moving into the mountains from the west. This
activity should be fairly light, but embedded heavy downpours will
be possible. Temps will be slightly above normal under plenty of
cloud cover.

Tuesday, the overnight band of precip should continue to weaken as
it enters the piedmont early in the morning. At the surface, the
cold front should push in from the north and is expected to reach
the southern edge of the CWA by late morning. The NC mountains may
clear out enough for showers and storms to develop by early AFTN,
while the piedmont will take longer to see much clear behind the
front. Temps will be well below normal across the area under cloud
cover, closer to normal in the mountains with some clearing. Deep
convection, mainly showers and garden-variety tstms will be mainly
confined to the Blue Ridge. A small heavy rain threat will continue
due to the very moist air mass still in place.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 2:30 PM EDT Monday:  A post frontal trough, or secondary wind
shift line, will ease through our forecast area Tuesday evening. We
will be taking POPS down to slight chance, or lower by morning.

It appears the model suite is allowing a surface high to extend from
Illinois to Pennsylvania, and south into the Carolina's for mid
week. It almost has a mini wedge configuration. Low level moisture
should be abundant nevertheless, and we will start the diurnal
cycle for POPS, perhaps slightly abvoe average.

We start with a minimum in POPS Wednesday evening, but the upper
level flow starts to back and allow a return of moisture. Also a
wave train of vort maxes are embedded in the flow. The POPS for
Wednesday night still remain in the chance category, but edge up.

A bit more sharpening of upper level features Thursday should signal
an uptick in POP configuration, as a result we have brought values
up accordingly.

Overall through this portion of the forecast cycle, it appears to be
a lull in the amount and coverage of precipitation, considering the
constuction of the entire forecast package. However, we still have
to be on guard for heavy rain potential, although at least in this
part of the forecast cycle it appears to have eased somewhat.

As far as any severe potential, pulse type storms certainly look
possible Wednesday. Thursday we will probably begin having the
influence of some larger synoptic forcing.

Temperatures for this part of the forecast should remain be average,
which remains in line with the previous forecast and new data.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 210 PM EDT Monday: the extended fcst picks up at 00z on
Friday with a very broad, low amplitude upper trof centered over
Eastern Canada and upper ridging persisting over the Western CONUS
and well to our east over the sub-tropical Atlantic. As we move
into the weekend, a more amplified upper trof begins to dig down
over the Northern Plains and Western Great Lakes as the upper ridge
persists over the Western CONUS. The upper trof axis is still not
expected to reach our area until the very end of the period, early
next week.

At the sfc, moist SLY return flow will be in place over the region
on Friday as a low slowly moves eastward across the Great Lakes and
brings its associated weak cold front towards the fcst area on Sat.
This scenario is about 24 hours faster than model runs this time
yesterday with the ECMWF being more progressive with the front than
the GFS. Beyond this point, the pattern evolution becomes more ambiguous
with the ECMWF trying to develop a secondary low in the wake of the
fropa late Sunday into early Monday and then quickly move that low
up the New England Coast. The GFS also tries to develop some sort of
weak system during this time frame, but it's not as coherent as the
ECMWF. Regardless, both models keep deeper moisture over the fcst
area thru the end of the period. As for the sensible fcst, precip
chances will remain elevated thru the period with high-end chance
to low-end likely PoPs each day and broken to overcast cloud cover.
The potential for isolated to widespread flooding remains elevated
with precipitable water fcst values 1 to 2 standard deviations above
normal thru most of the period. With the ample cloud cover expected,
high temps should remain a few degrees below normal with low temps
right around normal.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
At KCLT and Elsewhere: a very moist air mass in place will make for
a challenging set of TAFs. Showers are developing quickly, as low
stratus is scattering out across the area. Instability will be great
enough for some of these showers to develop into tstms from mid-aftn
thru the evening. Timing the best coverage is difficult, however, as
better forcing will come from the west, not in line with the best
instability. For KCLT, will time prevailing SHRA from 00-06z. Will
mention TSRA at the other sites, where instability and coverage is
expected to be greater. The overnight, a cold front will push in
from the north by daybreak Tuesday. A wind shift from SW to NE will
probably be in the 12-15z time frame at KCLT and the Upstate TAF
sites. There should be plenty of VFR-level cloud cover to limit fog
and low stratus. However, given the very moist air mass and
weakening winds near the front, there will likely be some
restrictions around. Most of the guidance actually develops more
widespread MVFR to possibly IFR CIGS just behind the front across
the piedmont after 12z (earlier at KAVL and KHKY). Guidance also
depicts another round of showers entering the mountains after about
06z, then entering the piedmont after 12z.

Outlook: Unsettled conditions continue through most of the week
as a frontal boundary remains nearby, moisture pools, and a series
of upper level waves pass overhead. Restrictions will be possible
with any showers and thunderstorms. Fog and low clouds may develop
each morning around daybreak, mainly in the mtn valleys but also
in areas that receive heavy rainfall the day before.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High  85%     Low   56%     Low   56%     Med   68%
KGSP       High 100%     High 100%     Med   71%     Med   68%
KAVL       High  96%     High  92%     Low   48%     Med   76%
KHKY       High 100%     Med   71%     Low   57%     Med   62%
KGMU       High  98%     High 100%     High  95%     Med   70%
KAND       High 100%     High 100%     Low   59%     Med   67%

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...JPT
NEAR TERM...ARK/CDG
SHORT TERM...TS
LONG TERM...JPT
AVIATION...ARK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
458 PM EDT Mon Aug 7 2017

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-081100-
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-
458 PM EDT Mon Aug 7 2017

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

.DAY ONE...Tonight.

Scattered to numerous showers and thunderstorms will periodically
move across the area tonight. The potential exists for these storms
to produce torrential rainfall. Some areas may experience multiple
rounds of such storms, resulting in locally significant accumulation
and possibly flash flooding.

In addition, a few of the storms could become severe with damaging
downburst winds the main threat. Cloud-to-ground lightning will be
noted as well. Move to a place of safety if storms approach.

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

..Tuesday...Heavy rain possible. Numerous showers and thunderstorms
are expected again. This will keep the threat for heavy rainfall in
place across the area.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.
..Friday...No hazardous weather is expected at this time.
..Saturday...No hazardous weather is expected at this time.
..Sunday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

Sturey

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
446 PM EDT MON AUG 7 2017

SCZ002-003-005-006-072115-
Pickens Mountains SC-Greater Pickens SC-Greenville Mountains SC-
Greater Greenville SC-
446 PM EDT MON AUG 7 2017

...A STRONG THUNDERSTORM WILL IMPACT WESTERN GREENVILLE AND CENTRAL
PICKENS COUNTIES UNTIL 515 PM EDT...

At 446 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles west of Pickens, moving east at 40 mph.

Locations to be impacted include...
Greenville Downtown, Easley, Pickens, Greenville Eastside, West
Greenville, Berea, Welcome, Travelers Rest, Liberty and
Slater-Marietta.

Wind gusts up to 40 mph 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.

&&

LAT...LON 3476 8284 3493 8289 3509 8237 3483 8229
      3481 8248 3482 8248 3482 8249 3480 8252
TIME...MOT...LOC 2046Z 255DEG 34KT 3487 8278

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
502 PM EDT MON AUG 7 2017

SCZ006-010-072130-
Anderson SC-Greater Greenville SC-
502 PM EDT MON AUG 7 2017

...STRONG THUNDERSTORMS WILL IMPACT SOUTHEASTERN GREENVILLE AND
NORTHEASTERN ANDERSON COUNTIES UNTIL 530 PM EDT...

At 502 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 5 miles southwest of Easley to 5 miles southeast
of Anderson, and moving northeast at 35 mph.

Locations to be impacted include...
Greenville Downtown, Anderson, Greenville Eastside, West Greenville,
Mauldin, Simpsonville, Welcome, Powdersville, Piedmont and Belton.

Wind gusts up to 40 mph 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.

&&

LAT...LON 3458 8269 3469 8274 3489 8235 3480 8222
      3464 8221 3459 8224 3454 8224 3450 8229
      3436 8265
TIME...MOT...LOC 2102Z 237DEG 30KT 3476 8265 3463 8252 3447 8256

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
515 PM EDT MON AUG 7 2017

SCZ003-006-007-072145-
Greenville Mountains SC-Spartanburg SC-Greater Greenville SC-
515 PM EDT MON AUG 7 2017

...STRONG THUNDERSTORMS WILL IMPACT NORTHERN GREENVILLE AND
NORTHWESTERN SPARTANBURG COUNTIES UNTIL 545 PM EDT...

At 514 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 11 miles northeast of Pickens to 9 miles
northwest of Greenville Downtown to near Easley, and moving northeast
at 40 mph.

Locations to be impacted include...
Greenville Downtown, Greenville Eastside, West Greenville, Greer,
Taylors, Berea, Welcome, Travelers Rest, Duncan and Lyman.

Wind gusts up to 40 mph 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.

&&

LAT...LON 3480 8247 3482 8249 3491 8250 3498 8255
      3498 8253 3501 8254 3501 8260 3506 8260
      3507 8257 3507 8266 3518 8247 3518 8246
      3516 8246 3517 8244 3521 8239 3518 8237
      3520 8229 3519 8212 3511 8206 3486 8210
TIME...MOT...LOC 2114Z 244DEG 34KT 3501 8259 3494 8252 3484 8259

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
521 PM EDT MON AUG 7 2017

SCZ006-007-010-012-072200-
Laurens SC-Anderson SC-Spartanburg SC-Greater Greenville SC-
521 PM EDT MON AUG 7 2017

...STRONG THUNDERSTORMS WILL IMPACT NORTHWESTERN LAURENS...
SOUTHEASTERN GREENVILLE...SOUTHWESTERN SPARTANBURG AND NORTHEASTERN
ANDERSON COUNTIES UNTIL 600 PM EDT...

At 521 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 4 miles southwest of Greenville Downtown to 17
miles southeast of Easley to 15 miles east of Anderson, and moving
northeast at 35 mph.

Locations to be impacted include...
Laurens, Greenville Downtown, Spartanburg, Greenville Eastside,
Mauldin, Simpsonville, Five Forks, Fountain Inn, Powdersville and
Piedmont.

Wind gusts up to 40 mph 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.

&&

LAT...LON 3442 8245 3464 8242 3479 8253 3500 8197
      3482 8191 3452 8195 3445 8229 3447 8231
      3448 8231 3448 8232 3443 8240
TIME...MOT...LOC 2121Z 246DEG 31KT 3483 8247 3467 8235 3452 8237

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
551 PM EDT MON AUG 7 2017

SCZ007-012-072215-
Laurens SC-Spartanburg SC-
551 PM EDT MON AUG 7 2017

...STRONG THUNDERSTORMS WILL IMPACT NORTHERN LAURENS AND SPARTANBURG
COUNTIES UNTIL 615 PM EDT...

At 551 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from 11 miles east of Greenville Downtown to 17 miles
southwest of Spartanburg to 9 miles west of Laurens, and moving
northeast at 40 mph.

Locations to be impacted include...
Spartanburg, Woodruff, Duncan, Lyman, Pacolet, Cowpens, Wellford,
Roebuck, Gray Court and Pacolet Mills.

Wind gusts up to 40 mph 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 3471 8218 3478 8215 3480 8217 3480 8216
      3485 8222 3492 8222 3509 8182 3504 8181
      3503 8179 3493 8176 3493 8174 3491 8171
      3483 8179 3461 8185 3460 8184 3454 8219
TIME...MOT...LOC 2151Z 241DEG 33KT 3489 8220 3475 8212 3455 8218

HG