Severe Thunderstorm Warning 230, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
451 PM EDT Fri Jul 6 2018

.SYNOPSIS...
A cold front will cross the region this afternoon and evening
bringing widespread showers and thunderstorms with it. In its
wake, cooler and drier air will move over the area through the
weekend. Mostly dry conditions will persist into next week with
a warming trend expected.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 445 pm...having to make a bunch of adjustments to precip
prob...mainly to raise into the Likely range over metro CLT and
much of Upstate SC...as storms continue to develop and propagate
along outflow boundaries into that part of the fcst area. Lots of
leftover stratiform precip and embedded deeper convection across
NC...so will not lower any precip chances just yet. The convection
was wreaking havoc on the temp trends, with lots of places cooled
off significantly by the precip. Think there is time for some
rebound, though, so there will be several updates to temp/dewpt as
we work into the evening. Still cannot rule out a few more severe
multicells on better-developed cold pools, in spite of an air mass
with relatively poor dCAPE values, probably because of some high
sfc delta Theta-e values. Also, shear over cold pool-depth should
be just enough to support continued cell clustering, enhancing
the downburst threat. In addition to the severe potential, PWATs
that are in the 90th percentile of climatology (around 1.75" at
KFFC at 12Z) along with deliberate cell movement and some training
potential will yield a locally excessive rainfall threat.

A moist easterly flow developing north of the boundary tonight
will support continued chances for showers through much of the 1st
period, especially along the eastern escarpment of the Blue Ridge.
Min temps will settle close to climatology.

As expansive/anomalously high pressure expands from the Great Lakes
into the Northeast and northern Mid-Atlantic late tonight through
tomorrow, resultant ageostrophic adjustment/cold air damming will
become established east of the Appalachians, with a combination
of CAD and persistent low cloud cover expected to result in max
temps about 10 degrees below climo, which would be out coolest day
around here in about 4 weeks. The air mass will therefore be much
more stable on Saturday, except perhaps around the southern and
western periphery of the forecast area, where the highest pops will
exist during the afternoon. Otherwise, pops will gradually increase
through the day, as drier air gradually filters in from the NE.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 230 PM EDT Friday: The ridging aloft which earlier retrograded
back to the western half of the CONUS, gradually will be shifting to
the east once again. Meanwhile surface high pressure from the New
England state wedges down into part of our forecast area (FA).

As drier air seeps into the region Saturday night and Sunday, we
should see a reduction of shower and thunderstorm activity (from
north to south) as high pressure at the surface and aloft become
dominant. It may be a bit of a slower process since moisture and
some instability are maintained. Overall however the trend should be
for less coverage or ending.

The two areas by later Sunday which we will still be carrying some
low end POPS is in our southern lakelands area and and parts of our
southwest NC mountains. At these locations the full wedge type
configuration does not become established, and therefore those
places remain rather moist and unstable, even though they will be
north of the surface front.

We dialed up similar POPS on Monday in the NC mountains, otherwise
we have kept it dry for the remainder of the FA. Otherwise, we will
be watching the tropics closely the next few days for situational
awareness.

In the temperature department, as ridging aloft builds back into the
region we will note temperatures creeping upward each day. Once
again the model signals are nearly the same and we plan to follow.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 210 PM EDT Friday: The extended fcst picks up at 00z on Tues
with steep upper ridging in place over the Western CONUS and broad
upper trofing over Eastern Canada. As we move into Wed, the upper
trof amplifies over New England and pushes the upper ridge farther
to the west. By Thurs, the trof axis begins to move off the Atlantic
Coast as the ridge tries to spread eastward. At the sfc, broad and
weakening high pressure will be lingering over the region to start
the period. In addition, a sub-tropical coastal low is expected to
be just off the Southeast Coast and nearly stationary. The larger
scale synoptic pattern is not expected to change significantly thru
the period, with broad and fairly weak high pressure persisting
over the region. The latest guidance has the above mentioned sfc
low gradually lifting NE and farther offshore as the period wears
on. Thus, it should not have a substantial impact on our sensible
weather. As for the sensible fcst, I kept a mostly diurnal PoP trend
for showers and thunderstorms each afternoon/evening. Temperatures
are expected to remain above normal and warm thru the period. They
should level off by Day 7 on Friday.

&&

.AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: convection is becoming fairly widespread
across the mtns and NC foothills this afternoon, and activity will
continue to roll S and SE into the the Piedmont/Upstate SC
throughout the afternoon and into the evening. Tempos for TSRA are
warranted at all terminals during this time. VCTS/VCSH linger
through about mid-evening, but chances for showers/possible TSRA
will linger well into the overnight, as a cold front sags south
across the area. Winds will become light N/NW by evening in the wake
of this front, then gradually turning toward the NE overnight into
Sat morning and increasing to 10-15 kts at most locales by
mid-morning. Moist E/NE flow north of the front will likely result
in development and expansion of low clouds around sunrise, with
IFR/low MVFR cigs advertised at most terminals.

Outlook: Cigs restrictions and showers may persist into Saturday
afternoon as the frontal boundary settles south of the region.
Unsettled conditions could linger through early next week in the
vicinity of the stalled or dissipating front.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High 100%     High 100%     High  81%     High  87%
KGSP       High 100%     High 100%     High  83%     High  93%
KAVL       High 100%     High 100%     High  89%     High  84%
KHKY       High 100%     High 100%     High  81%     High  87%
KGMU       High 100%     High 100%     High  85%     High  97%
KAND       High 100%     High 100%     High  98%     High  98%

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...JDL/PM
SHORT TERM...TS
LONG TERM...JPT
AVIATION...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
540 AM EDT Fri Jul 6 2018

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-070945-
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-
540 AM EDT Fri Jul 6 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 thunderstorms today and tonight will produce cloud-to-
ground lightning and locally heavy rainfall. Stronger storms could
produce localized flooding and gusty winds.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

..Saturday...No hazardous weather is expected at this time.
..Sunday...No hazardous weather is expected at this time.
..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.

.SPOTTER INFORMATION STATEMENT...

None.

SGL

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
421 PM EDT FRI JUL 6 2018

NCZ070-071-082-SCZ009-062100-
Gaston NC-Union NC-Mecklenburg NC-York SC-
421 PM EDT FRI JUL 6 2018

...STRONG THUNDERSTORMS WILL IMPACT MECKLENBURG...EASTERN GASTON...
SOUTHWESTERN UNION AND NORTHEASTERN YORK COUNTIES UNTIL 500 PM EDT...

At 420 PM EDT, Doppler radar indicated a cluster of strong
thunderstorms along a line extending from 10 miles southwest of
Huntersville to 6 miles north of Uptown Charlotte to 11 miles
northwest of Monroe, and moving south at 15 mph.

Locations to be impacted include... Charlotte, Huntersville,
Gastonia, and Rock Hill.

Wind gusts up to 45 mph, pea size hail and torrential rainfall rates
up to 3 inches per hour 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. Power outages may
result.

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.

These storms 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.

&&

LAT...LON 3482 8074 3482 8080 3494 8078 3508 8091
      3503 8090 3501 8091 3499 8089 3492 8086
      3488 8088 3494 8096 3510 8126 3541 8108
      3540 8096 3541 8096 3539 8081 3507 8066
TIME...MOT...LOC 2020Z 020DEG 14KT 3533 8100 3531 8083 3508 8072

08

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
427 PM EDT FRI JUL 6 2018

NCZ048-052-053-062100-
Buncombe NC-Haywood NC-Madison NC-
427 PM EDT FRI JUL 6 2018

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN MADISON...EAST
CENTRAL HAYWOOD AND NORTHWESTERN BUNCOMBE COUNTIES UNTIL 500 PM
EDT...

At 426 PM EDT, Doppler radar was tracking a strong thunderstorm near
Marshall, moving south at 20 mph.

Locations to be impacted include...
Marshall, Leicester, Canto, Luck, Spring Creek and Walnut.

Wind gusts up to 55 mph and dime size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Dime to nickel size hail can cause considerable damage to vehicles.
Consider moving vehicles to a covered storage area before the storm
arrives.

Please report damaging winds, hail, or flooding to the National
Weather Service Greenville-Spartanburg by calling toll free, 1, 800,
2 6 7, 8 1 0 1, or by posting on our Facebook page, or Tweet it using
hashtag nwsgsp. Your message should describe the event and the
specific location where it occurred.

&&

LAT...LON 3584 8284 3584 8266 3560 8261 3560 8290
TIME...MOT...LOC 2026Z 358DEG 16KT 3577 8274

08

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
454 PM EDT FRI JUL 6 2018

GAZ026-028-029-SCZ007-010>014-019-062215-
Elbert GA-Hart GA-Franklin GA-Laurens SC-Anderson SC-Abbeville SC-
Union SC-Greenwood SC-Chester SC-Spartanburg SC-
454 PM EDT FRI JUL 6 2018

...A CLUSTER OF THUNDERSTORMS WILL IMPACT CENTRAL FRANKLIN...
ELBERT...HART...LAURENS...SOUTHWESTERN CHESTER...SOUTHEASTERN
SPARTANBURG...SOUTHERN ANDERSON...ABBEVILLE...UNION AND GREENWOOD
COUNTIES UNTIL 615 PM EDT...

At 452 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from near Carnesville
Georgia, through Anderson County, to Laurens, to Union, and moving
southeast at 20 mph.

Locations to be impacted include...
Greenwood, Laurens, Union, Abbeville, Elberton, Hartwell,
Carnesville, Clinton, Homeland Park and Honea Path.

Wind gusts up to 50 mph, half inch hail and torrential rainfall
rates up to 3 inches per hour will be possible with the strongest
storms 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.

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.

Please report damaging winds, hail, or flooding to the National
Weather Service Greenville-Spartanburg by calling toll free, 1, 800,
2 6 7, 8 1 0 1, or by posting on our Facebook page, or Tweet it using
hashtag nwsgsp. Your message should describe the event and the
specific location where it occurred.

&&

LAT...LON 3402 8224 3397 8231 3406 8233 3408 8248
      3401 8260 3396 8257 3401 8293 3424 8318
      3447 8331 3450 8215 3490 8165 3456 8117
      3457 8142 3450 8142 3445 8154 3453 8164
      3430 8190 3420 8194 3413 8187 3395 8204
TIME...MOT...LOC 2052Z 317DEG 19KT 3439 8320 3443 8251 3446 8213 3477
8169

08

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