Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
304 PM EDT Mon Aug 19 2019

.SYNOPSIS...
An area of low pressure and elevated moisture will persist across
the western Carolinas and northeast Georgia through Wednesday. A
moist cold front will approach the region Thursday and become
stationary on Friday. The front will gradually settle south of the
area through the weekend as high pressure builds in from the north
and maintains cooler than normal temperatures.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 255 PM EDT Monday: Situated in between a ridge of
high pressure both to the west and east, as a few upper shortwaves
swing through overhead, an unsettled weather pattern has already
blossomed across the western Carolinas and northeast Georgia this
afternoon. With temperatures currently in the upper 80s/lower 90s
and dewpoints in the lower 70s, latest mesoanalysis depicts sbCAPE
values of 2000-3500 J/kg across the area, with plenty of dry air in
place at the mid levels. Thus, would not entirely rule out a few of
these storms becoming strong to severe before the end of the day,
with microbursts, as noted in previous discussions, as a
possibility. In addition, with the aforementioned temperatures and
dewpoints, though below heat advisory criteria, heat indices in the
mid to upper 90s outside the mountains will continue through this
evening.

Expect convection to linger into the evening hours, gradually waning
into tonight, though a few light showers overnight could not be
entirely ruled out. With the expectation of mid to high level clouds
overhead through the overnight hours as weak sfc low meanders north
into the area, expect min temperatures to remain above normal. Some
of the guidance/fcst soundings continued to suggest fog development
towards daybreak on Tuesday, but confidence is fairly low attm given
anticipated cloud cover.

A similar pattern is expected on Tuesday, though the potential for
strong to severe storms will be slightly less. Temperatures will
remain just above normal, with heat indices in the low to mid 90s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 1:35 PM EDT Monday: the short-term forecast picks up at 00z on
Wednesday with our region stuck between upper ridging to the west and
weaker upper ridging over the Western Atlantic. On Wed, broad upper
trofing begins to dig down across the Great Lakes as the ridges amplify
on either side of us. On Thurs, the upper trof persists over the Great
Lakes as heights fall over our area and upper-lvl flow strengthens
from the west. At the sfc, the Bermuda High will continue to be the
main driver of our synoptic pattern thru most of the period, keeping
a moist, tropical airmass over the CWFA. On Thurs, a moist cold front
will make its way southeastward from the Ohio River Valley and approach
the fcst area early Thurs. The front is expected to move through the
CWFA late Thurs and into early Fri. No major changes were needed for
the sensible fcst with above climatology PoPs each day, with Thurs
carrying likely PoPs across roughly the northern half of the CWFA.
Instability will be decent each day/evening, with little in the way
of shear on Wed and a bit more on Thursday as the front approaches.
Instability will probably be limited to some extent on Thursday as
cloud cover is expected to increase thru the day. Temperatures will
remain just above normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 115 PM EDT Monday: An slow moving cold front will continue
pushing over the FA to begin the ext range. With the upper flow
becoming more diffuse the front will become broad and stall while
slowly drifting south thru Fri. Good agreement is seen in the latest
guidance in developing a 1024 mb Canadian high over the Midwest
early Fri and traversing it east thru the period and this shud setup
a wedge scenario across the FA thru the weekend.

In the meantime...good instability will be had along and ahead of
the sfc bndry which will instigate deep tstms. Deep layered
shear remains quite low however...so the mode will likely remain
pulsey with multicellular lines probable into the evening. The
latest GFS is the quickest with bringing in ne/ly flow within
the sfc-h8 layer Fri afternoon at KHKY and then arnd 00z at
KGSP. The other op models are much slower with the wedge idea
development arnd 12z Sat. So...some uncertainty is had with the
onset time of more stable air and a general decrease in thunder
activity Fri evening.

The wedge does look to become mature by Sat afternoon tho and expect
Atl and GOM moisture adv to reinforce the pattern...which could
linger into Mon per the GFS. Max temps on Fri will be right arnd
normal...then below normal temps by a couple cats or so over the
weekend. PoPs will remain abv normal outside the mtns in isentropic
lift...with the wedge bndry likely become convectively active across
the extreme ern to sw/rn zones each afternoon Sat and Sun.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: VFR prevails at all TAF sites this afternoon,
with convection already blossoming across the entire forecast area.
Thus, all TAF sites have prevailing VCSH/VCTS for the afternoon
hours, with TEMPO groups to account for possible short-lived flight
restrictions due to any SHRA/TSRA that moves over a TAF site. Expect
convection to wane into tonight, with lingering mid to high level
clouds and light winds. Latest fcst soundings continue to suggest
the potential for stratus, while some are hinting at fog
development. Confidence is low in regards to fog given the
anticipated cloud cover, but attm, could not entirely rule it out
towards daybreak.

Outlook: The potential for afternoon/evening showers and
thunderstorms is expected to increase throughout the week, as a cold
front approaches from the NW into Thursday. Morning fog and low
stratus will be possible each day across the mountain valleys.
Otherwise, expect VFR.

Confidence Table...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High  94%
KAVL       High 100%     High 100%     Med   68%     High  96%
KHKY       High 100%     High 100%     High  93%     High 100%
KGMU       High 100%     High 100%     High 100%     High  90%
KAND       High 100%     High 100%     High  92%     High  90%

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...SBK
NEAR TERM...SGL
SHORT TERM...JPT
LONG TERM...SBK
AVIATION...SGL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
432 AM EDT Mon Aug 19 2019

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-200845-
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-
432 AM EDT Mon Aug 19 2019

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 are expected to develop across the area this
afternoon, especially near the eastern escarpment of the Blue Ridge
Mountains. Cloud-to-ground lightning, brief heavy downpours, and
locally gusty winds will be the primary threats with these
thunderstorms. A few of the storms may be strong enough to produce
damaging wind gusts.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

HG

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