Severe Thunderstorm Warning 170, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
250 PM EDT Sat Jul 8 2017

.SYNOPSIS...
Seasonably warm temperatures and afternoon showers and thunderstorms
will continue as a front pushes through the area late tonight. Drier
air will build in Sunday and Monday with more humid and unsettled
weather expected through the second half of next week as the frontal
boundary creeps back into the area from the south. A more
substantial system will move through the area near the end of next
week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 245 PM EDT Saturday:  Convection firing mainly over the
higher terrain as of 18Z, but suspect storms will only get stronger
and more numerous from there as a short wave comes into play
as it crosses the region through early evening. Downslope flow
immediately to the lee of the Blue Ridge might put a damper on
some development, but cu field continues to blossom in the I-85
corridor and east, so we should not have any problems with the
storm environment there. Speaking of which, latest mesoanalysis
shows sbCAPE in the 1500-3000 J/kg range, thus we are well on our
way to having moderate instability for the afternoon ahead of a
boundary dropping down from the N. Meanwhile, dCAPE greater than
800 J/kg has developed across the entire fcst area. Think we have
just about all the ingredients we need for scattered to numerous
thunderstorms this afternoon with a good chance that several
of them will go severe with wind damage the main threat. Better
shear means a better chance for organization as cold pools merge
and expand east of the mtns. Agree with SPC Day 1 Slight Risk over
the wrn Piedmont of NC as that area stands a good chance of seeing
severe wind producing multicells this afternoon.

The passage of the short wave this evening should carry the
bulk of the convection to the s/e of the fcst area by around
sunset, followed by the passage of the surface boundary. Some
activity could linger on the SE fringe into the late evening,
but otherwise, drier air will spill in across the region behind
the boundary. Some mtn valley fog is expected around daybreak
Sunday, but otherwise it should be a cooler day, maybe a few deg
on the cool side of normal. However, the air mass should be drier,
which hopefully will make it not as uncomfortable as the past few
days. An isolated shower or storm could develop near the fall line,
so a slight chance was retained on the southeast fringe.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 130 PM Saturday: The upper trough over the eastern CONUS will
deamplify Monday thru Tuesday, as a subtropical ridge reassert
itself into the Southeast. At the surface, a Bermuda high pattern
will gradually set back up across the region. It will take a couple
days for moisture and instability to return to typical mid-July
levels. So PoPs will remain below climatological coverage for mainly
diurnal convection. Temps will be near or slightly above normal.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 100 PM EDT Saturday: The medium range remains in a pretty
typical July holding pattern with chances of scattered convection
each afternoon. Upper heights will rise briefly on Wednesday, though
continued moist southerly flow courtesy of an elongated Bermuda high
and some slight upper forcing accompanying a weak upper shortwave
will likely still lead to scattered diurnal convection. Upper
troughing begins to take shape again for the eastern CONUS on
Thursday, and a stalled remnant frontal boundary will provide a
focus for diurnal convection. The upper trough deepens with a
shortwave approaching our CWA by Friday, likely leading to sustained
showers and thunderstorms overnight in a more non-diurnal pattern.
Decent instability should develop each day, so a few pulse-type
severe storms are possible. Temperatures will begin the period just
above average, and will fall to near average as heights fall aloft.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and Elsewhere:  VFR through the period at all sites with
the possible exception of afternoon MVFR convection, as well as
early morning MVFR fog restrictions at KAVL Sunday morning. The
convection-allowing model guidance suggests a good chance of
semi-organized storms developing over the mtns and then moving
east across the region through 00Z...thus all sites but KHKY get
a four-hour TEMPO to account for this. A Well mixed boundary layer
will keep wind SW through the afternoon with some gusts possible,
until sfc boundary moves through in the early evening to bring
direction around to NW for the rest of the evening, then light N
overnight. On Sunday, expect only high level clouds with a light
NE wind.

Outlook: Quiet conditions will prevail on Sunday afternoon with a
stable air mass behind the cold front.  Chances for restrictions
will gradually increase into next week thanks to diurnal showers
and thunderstorms, as well as overnight/morning fog.

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  91%     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 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...Carroll
NEAR TERM...PM
SHORT TERM...ARK
LONG TERM...Carroll
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
353 PM EDT Sat Jul 8 2017

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-092000-
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-
353 PM EDT Sat Jul 8 2017

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

.DAY ONE...This Afternoon and Tonight.

A cold front will continue to push across the western Carolinas and
Northeast Georgia through this evening. Scattered to numerous
thunderstorms will continue to develop along and ahead of this
front. With the added lift...some of these storms will become quite
strong or severe. The main threats will be damaging winds and large
hail...along with cloud to ground lightning.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

..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.
..Friday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Skywarn spotters are requested to forward any reports of large hail
and damaging winds to our office.

ARK

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