Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
437 PM EDT Sun Aug 5 2018

.SYNOPSIS...
A Bermuda high pattern should linger across the region through the
early part of the week, allowing for seasonally warm temperatures
and afternoon showers and thunderstorms. A cold front will
eventually drop down across the region during the middle part of
the week, and is expected to stall just to our south for the late
part of the week.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 435 PM EDT Sunday: Moderate instability has developed over
much of the CWFA this afternoon. However, convective initiation has
been better across the mountains where differential heating is
better. Not much in the way of DCAPE where better storm coverage is
occurring. That said, can't rule out a few strong storms or isolated
damaging downburst. The storms are showing good movement, so even
though isolated heavy rain is likely, the flood threat is low unless
storms can train over the same area. CAMs and the destruction of
SBCAPE around nightfall, argue for a rapid descent of storm
intensity and coverage after dark.

Synoptic conditions remain mild through Monday afternoon, albeit
with enough diurnal instability to support a few afternoon
thunderstorms today and tomorrow.  Surface high axis lies just east
of the area giving light southwesterly to variable winds, which
become more westerly by Monday afternoon as high center edges
eastward and upstream trough forms from the Great Lakes Region to
the Southern Plains.  Weak upper ridge over the East also edges
eastward, being replaced by an upper trough over the Great Lakes.
Through the near term, there will be little change in airmass,
though light westerly surface flow from Tennessee may begin some
drying in the mountains late on Monday.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 2:30 PM Sunday: A segment of the western Atlantic high
pressure system (in our vicinity) will break down during this part
of the forecast cycle. The reorientation of the aforementioned
feature, to the south, will open up the door for a wave of energy to
rotate around the northern periphery of the high, and into our area
Monday night. We probably will have some unused instability in
place, as a result we will keep POPS going overnight, albeit on the
chance side. It appears our mountains and eastern forecast areas
(FA) stand the better chances of showers and thunderstorms then.

The thermal pattern will be on the increase Tuesday, dewpoints will
be climbing, while SBCapes reach the 1500-2500 J/kg range. We should
ignite thunderstorms in the mountains, and also in proximity of an
area of surface convergence, Tuesday afternoon and evening, in parts
of the piedmont. Precipitable water values will again be flirting in
the 1.75 to +2.00 inches, therefore efficient rain producers will be
possible. QPF response from the models has not been terribly
impressive, but it something to monitor.

We let the precipitation in the forecast drop off to minimal values
Tuesday night, but kept higher chance values in the mountains where
response continues.

Meanwhile, the upper level trough of low pressure will be shifting
from Minnesota to Oklahoma on Tuesday, reaching the western Great
Lakes to the Tennessee Valley Wednesday. This is one of the messy
parts of the forecast, as this positive tilted upper level feature
approaches. We will once again have a prefrontal surface trough in
place Wednesday, heights falling, and the primary cold front out to
the west. Considering we will be hot and unstable we start ramping
up POPS, reaching likely in the mountains during Wednesday afternoon.

Temperatures are tricky Tuesday and Wednesday. We were tempted to go
above guide on both days, but were held back because of the idea of
clouds and convection, or leftovers. If precipitation holds off, or
delayed starting, I could see mid 90s outside the mountains of NE
Georgia, and across the piedmont of SC and NC. Currently our heat
indices are running in the mid and upper 90s Tuesday, with a few
heat indices reaching around 100 degrees Wednesday, primarily in the
piedmont. Warm and muggy at night.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 200 PM EDT Sunday: The latter half of the week looks active as
upper troffing re-asserts itself over the east starting Wednesday
night with the passage of a short wave. This is expected to bring
a sfc boundary down across the region from the NW overnight, which
should help prolong the shower and thunderstorm activity until the
early morning hours on Thursday. The front should stall to our south
on Thursday where it will linger into the weekend, reinforced by
the passage of several weak waves through the relatively shallow
upper trof. This boundary will provide a focus for diurnally
enhanced convection through the rest of the period. Fortunately,
lingering weak ridging at 850mb along the Gulf Coast will tend
to keep us cut off from the deeper gulf moisture, and none of the
upper waves are particularly dynamic. The main concern will be the
possibility of heavy rain closer to the boundary where moisture
would tend to pool, particularly in light of our recent wet period.
As it stands right now, it looks like the boundary would affect
mainly the southernmost zones with drier air managing to spread
across the NC part of the fcst area, but the proximity is close
enough to keep some concern in mind, being that we are talking about
day 4 and beyond. The fcst will keep good chance to likely precip
probability each period. Temps will drop back to something at or
slightly below normal, assuming the boundary ends up to our south.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere:  High pressure center is just east of the area
giving light and somewhat variable winds.  General anticyclonic flow
over the area will, at times, give a southwesterly wind direction
when things are not variable.  Modest instability and little forcing
today and tomorrow, but diurnal factors will give some chance for
showers and thunderstorms this afternoon and Monday afternoon.
Current radar and high-res model trends have widely scattered
coverage, rapidly declining after 00Z.  Models also have a fair
amount of reduced visibility and lowered CIGs in the early morning
hours in mountain valleys and to some extent in the piedmont, which
will dissipate by 15Z.

Outlook: Diurnal, scattered afternoon thunderstorms will continue
through much of the week. Associated morning restrictions will be
possible each day, especially across the mountains.

Confidence Table...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       High 100%     High 100%     Med   75%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High  81%     High 100%
KHKY       High 100%     High  93%     Med   75%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High  93%     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...PM
NEAR TERM...RWH/WJM
SHORT TERM...TS
LONG TERM...PM
AVIATION...WJM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
405 PM EDT Sun Aug 5 2018

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-061200-
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-
405 PM EDT Sun Aug 5 2018

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

.DAY ONE...Scattered thunderstorms will continue to roam across the
countryside through the evening. The primary threats will be cloud-
to-ground lightning, heavy rain and gusty winds. Thunderstorms will
then wane during the overnight hours.

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

Periodic thunderstorm episodes will continue during the upcoming
workweek. Impacts would include cloud-to-ground lightning, heavy
rainfall and gusty winds.

Additionally, heat indices outside the mountains will range from 95
to 100 degrees Tuesday and Wednesday.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
111 PM EDT SUN AUG 5 2018

NCZ082-051815-
Union NC-
111 PM EDT SUN AUG 5 2018

...A CLUSTER OF THUNDERSTORMS WILL IMPACT UNION COUNTY UNTIL 215 PM
EDT...

At 109 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 12 miles west of
Wadesboro to 10 miles southwest of Monroe, and moving southeast at 35
mph.

Locations to be impacted include...
Monroe, Wingate, Waxhaw, Marshville, Mineral Springs, Sturdivants,
Wesley Chapel, Marvin, Unionville and Jaars.

Very heavy rainfall rates of 1 to 2 inches per hour will be possible
in these areas. Cloud to ground lighning and gusty winds will also
be noted.

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 3481 8032 3482 8075 3486 8079 3494 8078
      3497 8081 3511 8029
TIME...MOT...LOC 1709Z 313DEG 30KT 3502 8029 3491 8071

STUREY

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
219 PM EDT SUN AUG 5 2018

SCZ001-004-005-051845-
Greater Pickens SC-Greater Oconee SC-Oconee Mountains SC-
219 PM EDT SUN AUG 5 2018

...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL PICKENS AND CENTRAL
OCONEE COUNTIES UNTIL 245 PM EDT...

At 218 PM EDT, Doppler radar was tracking a strong thunderstorm near
Walhalla, moving southeast at 15 mph.

Locations to be impacted include...
Seneca, Walhalla, Westminster, Oconee State Park, Lake Keowee and
Oakway.

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.

&&

LAT...LON 3479 8322 3492 8307 3483 8290 3481 8290
      3482 8287 3477 8278 3457 8301
TIME...MOT...LOC 1818Z 312DEG 13KT 3481 8308

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
245 PM EDT SUN AUG 5 2018

SCZ001-004-005-051915-
Greater Pickens SC-Greater Oconee SC-Oconee Mountains SC-
245 PM EDT SUN AUG 5 2018

...A COUPLE STRONG THUNDERSTORMS WILL IMPACT SOUTHWESTERN PICKENS
AND SOUTHEASTERN OCONEE COUNTIES UNTIL 315 PM EDT...

At 244 PM EDT, Doppler radar was tracking a couple thunderstorm near
Walhalla, moving southeast at 15 mph.

Locations to be impacted include...
Clemson, Seneca, Walhalla, Central, Westminster, Lake Keowee,
Townville, Oakway and Fair Play.

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...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

&&

LAT...LON 3451 8297 3474 8323 3488 8301 3470 8273
      3467 8279 3456 8290
TIME...MOT...LOC 1844Z 316DEG 14KT 3477 8303

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
306 PM EDT SUN AUG 5 2018

GAZ017-018-051930-
Stephens GA-Habersham GA-
306 PM EDT SUN AUG 5 2018

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN STEPHENS AND
CENTRAL HABERSHAM COUNTIES UNTIL 330 PM EDT...

At 306 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles northeast of Clarkesville, moving southeast at 20 mph.

Locations to be impacted include...
Toccoa, Clarkesville, Tallulah Falls, Hollywood, Turnerville and
Boydville.

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.

&&

LAT...LON 3468 8357 3472 8349 3473 8348 3473 8346
      3474 8344 3475 8343 3458 8324 3448 8346
TIME...MOT...LOC 1906Z 316DEG 24KT 3464 8346

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
346 PM EDT SUN AUG 5 2018

GAZ018-026-SCZ001-004-052015-
Franklin GA-Stephens GA-Greater Oconee SC-Oconee Mountains SC-
346 PM EDT SUN AUG 5 2018

...A STRONG THUNDERSTORM WILL IMPACT NORTH CENTRAL FRANKLIN...
STEPHENS AND SOUTHWESTERN OCONEE COUNTIES UNTIL 415 PM EDT...

At 346 PM EDT, Doppler radar was tracking a strong thunderstorm near
Toccoa, moving southeast at 15 mph.

Locations to be impacted include...
Toccoa, Martin, Avalon, Eastanolee and Boydville.

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.

&&

LAT...LON 3441 8326 3458 8341 3460 8340 3468 8326
      3458 8307
TIME...MOT...LOC 1946Z 313DEG 15KT 3458 8326

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
513 PM EDT SUN AUG 5 2018

NCZ065-509-510-SCZ003-052145-
Henderson NC-Polk Mountains NC-Eastern Polk NC-
Greenville Mountains SC-
513 PM EDT SUN AUG 5 2018

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN HENDERSON...
SOUTHWESTERN POLK AND NORTHEASTERN GREENVILLE COUNTIES UNTIL 545 PM
EDT...

At 513 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles west of Columbus, or near Saluda, moving southeast at 20 mph.

Locations to be impacted include...
Columbus, Tryon, Saluda, East Flat Rock and Mill Spring.

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.

&&

LAT...LON 3525 8210 3519 8216 3519 8222 3514 8222
      3510 8226 3528 8241 3536 8230
TIME...MOT...LOC 2113Z 309DEG 19KT 3527 8229

KRENTZ