Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
237 PM EDT Sun Jul 2 2017

.SYNOPSIS...
High pressure centered over the western Atlantic and a broad upper
level trough will remain over the eastern part of the nation for the
better part of the next week. A weak cold front will linger over the
Carolinas and northern Georgia early this week, helping to generate
showers and storms. Another upper level disturbance will approach
our area toward the end of the week, further enhancing the coverage
of showers and storms at that time.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 2:15pm EDT Sunday: Dewpoints today are several degrees below
yesterday, except in western parts of the CWA where dewpoints still
reach the low 70s.  Weak surface convergence along and east of the
mountains is helping to focus some showers currently developing
along and east of the mountains.  As CAMs have been predicting,
showers are more significant in western areas where moisture is
better.  Somewhat reduced CAPE over yesterday and subdued
max-delta-thetae levels along with continued low wind shear levels
all suggest limited chances for severe this afternoon, though an
isolated strong outflow can not be ruled-out.  Shower activity
should continue through the afternoon spreading southeastward off of
the mountains, before diurnally ending this evening.  A few light
rain showers may continue overnight.  Following a day of warmth and
weak surface flow, surface dewpoints recover a couple degrees on
Monday and afternoon showers and thunderstorms are again forecast.

Synoptically, weather is dominated by a weak mid-level trough over
the southeast CONUS that makes little eastward progress over the
next 24 hours, along with a weak surface trough along the
mountains.  Surface winds will be light and humidity high, with
chances for mainly afternoon thunderstorms.  A couple weak upper
level disturbances will help to support thunderstorms this afternoon
and on Monday.  With high humidity, tonight's lows will be a couple
degrees above normal with highs today and Monday near normal.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM EDT Sunday: The showers and thunderstorms, associated
with an upper level wave, a very moist atmosphere, and subtle
surface convergence, will slowly wane Monday night. However, since
there remains some semblance of forcing throughout the night, we
will not completely drop the POPS as activity lingers.

The models appear to have split into two camps for Tuesday and
Wednesday, with the NAM lifting the central Mississippi Valley upper
level low pressure system to the northeast, similar to the old
European model. Meanwhile, the GFS and Canadian models still string
out pockets of energy riding the southern end of the westerlies.

We will follow with the current trend with ripples of energy passing
through our forecast area (FA) through Wednesday. As a result there
will be periods of enhanced POPS, as overall atmospheric conditions
will not have changed. A note worth mentioning, although our POPS
will remain elevated, we have brought them down just a notch,
providing some weight to the NAM and European models. Once again at
night we will adjust POPS down but not completely cut.

Precipitable water values certainly remain elevated, therefore
locally heavy rain will be possible with any of these storms.

The temperature department seems rather stable from the latest set
of guidance, compared to past performance. Therefore only minor
adjustments were needed.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 100 pm Sunday: A long wave trough will become re-established
across the East early in the period, as a relatively strong short
wave migrates from the Ohio Valley into the upper Mid-Atlantic.
Attendant cold front is expected to bring solid chance to likely
probabilities for convection by Thu afternoon. Deep layer shear may
become adequate by the end of the day to support some degree of an
organized severe weather threat, especially farther north across the
forecast area.

Under the influence of weak continental high pressure, the global
models generally depict drier and more stable air filtering into the
area by Friday, suggesting a lull in diurnal convective activity,
although considering the time of year, we opted to maintain small
(sub-climo) pops for PM showers/storms Fri afternoon. However, a
consensus of global deterministic models guidance and their ensemble
systems suggest another short wave trough will cross the
central/northern Appalachians over the weekend, allowing for another
weak fropa for our area, most likely in the Saturday/Sat night time
frame.  Pops therefore ramp back up to solid chances Saturday. While
the latest GFS is rather aggressive in building another (relatively)
dry air mass into the region by Day 7, the ECMWF is considerably
slower in pushing the boundary to the south and east of the forecast
area, suggesting another active convective day next Sunday. Again,
taking climatology and this inherent uncertainty into consideration,
opted to advertise chance/near climo pops for the new Day 7. Temps
are forecast to remain very close to climo through the period.

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: With weak upper trough west of the area and
still moist dewpoints in place, showers are expected to develop this
afternoon, primarily over the mountains, and move southeast.  Some
thundershowers will be possible this afternoon before things end
with diurnal boundary layer cooling.  Some improvement in moisture
and the approach of an upper impulse late on Monday will cause
another round of showers and thunderstorms Monday afternoon.  High
RH will also result in some morning patchy fog in places that are
typically prone to it.  Winds will be generally light and variable
to northerly.

Outlook: Moist and unsettled weather will continue through the
first half of the week as a weak frontal zone lingers across the
Carolinas. Expect more rounds of mainly afternoon/evening SHRA/TSRA
and some nocturnal restrictions.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High  86%     High  94%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High  97%     High  94%

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...JDL
NEAR TERM...WJM
SHORT TERM...TS
LONG TERM...JDL
AVIATION...WJM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
519 AM EDT Sun Jul 2 2017

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-030930-
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-
519 AM EDT Sun Jul 2 2017

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

.DAY ONE...Today and Tonight.

Isolated to scattered thunderstorms will develop this afternoon.
These storms will produce gusty winds and cloud to ground lightning.

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

..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..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.

.SPOTTER INFORMATION STATEMENT...

None.

Krentz

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
215 PM EDT SUN JUL 2 2017

SCZ001-021845-
Oconee Mountains SC-
215 PM EDT SUN JUL 2 2017

...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL OCONEE COUNTY UNTIL
245 PM EDT...

At 214 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles northeast of Walhalla, or 4 miles south of Salem. This storm
was nearly stationary.

Locations to be impacted include...
Lake Keowee and Salem.

Wind gusts up to 50 mph and half inch hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

Lake Keowee is in the path of this storm. Cloud to ground lightning
and gusty winds will create dangerous boating conditions.
Move to shore immediately.

&&

LAT...LON 3493 8291 3490 8290 3488 8291 3484 8290
      3481 8290 3479 8301 3484 8303
TIME...MOT...LOC 1814Z 246DEG 4KT 3483 8298

LANE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
241 PM EDT SUN JUL 2 2017

SCZ003-021930-
Greenville Mountains SC-
241 PM EDT SUN JUL 2 2017

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN GREENVILLE COUNTY
UNTIL 330 PM EDT...

At 241 PM EDT, Doppler radar was tracking a strong thunderstorm 11
miles south of Hendersonville, or 4 miles northeast of Pleasant Ridge
State Park, moving east at 10 mph.

Locations to be impacted include...
Glassy Mountain, Gowensville and North Saluda Reservoir.

Wind gusts up to 40 mph and pea size hail will be possible in these
areas.

LAT...LON 3518 8237 3519 8235 3519 8232 3520 8229
      3519 8222 3507 8222 3506 8223 3512 8250
      3516 8250 3518 8247 3518 8246 3516 8246
      3517 8244 3519 8242 3521 8239
TIME...MOT...LOC 1841Z 269DEG 4KT 3515 8243

CDG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
341 PM EDT SUN JUL 2 2017

GAZ026-022015-
Franklin GA-
341 PM EDT SUN JUL 2 2017

...A STRONG THUNDERSTORM WILL IMPACT FRANKLIN COUNTY UNTIL 415 PM
EDT...

At 341 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles west of Carnesville, moving east at 15 mph.

Locations to be impacted include...
Carnesville, Victoria Bryant State Park and Martin.

Wind gusts up to 40 mph and pea size hail will be possible in these
areas.

LAT...LON 3433 8339 3438 8339 3439 8338 3443 8338
      3446 8340 3447 8338 3448 8318 3451 8313
      3428 8317
TIME...MOT...LOC 1941Z 271DEG 11KT 3440 8337

CDG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
415 PM EDT SUN JUL 2 2017

GAZ028-SCZ010-022100-
Hart GA-Anderson SC-
415 PM EDT SUN JUL 2 2017

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN HART AND WEST
CENTRAL ANDERSON COUNTIES UNTIL 500 PM EDT...

At 415 PM EDT, Doppler radar was tracking a strong thunderstorm 6
miles north of Hartwell, or near Reed Creek, moving east at 10 mph.

Locations to be impacted include...
Reed Creek, Lake Hartwell and Sadlers Creek State Park.

Wind gusts up to 40 mph and pea size hail 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. Do not drive across
flooded roads.

Lake Hartwell is in the path of this storm. Cloud to ground
lightning and gusty winds will create dangerous boating conditions.
Move to shore immediately.

&&

LAT...LON 3441 8300 3448 8299 3449 8298 3452 8279
      3436 8281
TIME...MOT...LOC 2015Z 271DEG 10KT 3445 8295

CDG