Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
436 PM EDT Mon May 29 2017

.SYNOPSIS...
A series of weak cold fronts will cross the area through mid week.
Weak high pressure will make Thursday the drier day of the week.
Expect a stronger cold front to reach our region over the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 430 PM: Surface trough in place across the Piedmont with
approaching shortwave moving out of the Deep South and a bit of
an upper jetlet are the main forcing mechanisms for convection
this afternoon.  Deep upper trough/low over Lake Superior and upper
high just east of the Bahamas has led to strong southwesterly fetch
aloft, helping to draw moisture out of the Gulf. Given the abundant
deep shear invof the jetlet, multicell clusters are expected to
be the main storm mode. Main threat remains gusty/damaging winds,
though some low-end hail cannot be ruled out. Severe Tstm Watch
in effect for most of NE GA, the Upstate, and US 74 corridor
of the NC Piedmont, as well as adjacent portions of central GA
and SC. This watch primarily covers the threats associated with
storms developing within the CWFA. However, there is the additional
threat that clusters will organize over GA and move NE into our
area closer to sunset. While not a significant concern, at least
minor hydro threat cannot be ruled out with any training cells.

Convection should wane overnight and we lose most of our deep-layer
forcing as we push into tomorrow, but surface trough remaining
in place and southwest flow aloft continuing will allow for
diurnal convection, possibly enhanced a tad with the proximity
of the trough aloft. Best chances for Tuesday remain across the
Piedmont (especially SC/GA where the trough will linger) and the
SW mountains. Guidance is trending cooler for tomorrow but we're
warming up more than anticipated today so have erred on the warm
side, but still right at seasonal normals. Lows tonight a handful
or so degrees above.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 200 pm Monday: At long last, the axis of the upper trough,
that has been over the central Conus for what seems like ages, will
finally push to the East Coast by the end of the short term. This
will drag a weak cold front through our area on Wednesday. While
this should provide a focus for deep convection Wed afternoon,
coverage may not meet the expectations of a typical late-spring
fropa. Progged mid-level lapse rates are very poor, while forecast
soundings depict a well-mixed/relatively dry boundary layer. As a
result, no short term guidance source depicts anything more than
modest levels of CAPE Wed afternoon and pops will be advertised only
in the 20-30% range across much of the area (maybe 40% in the high
elevations near the Blue Ridge). Deep layer shear will remain
somewhat respectable, so a severe storm or two cannot be ruled out,
but the threat should be limited by the overall lack of robust
buoyancy.

By Thursday, guidance suggests weak but relatively dry high pressure
should be building into the area, limiting diurnal destabilization.
In fact, most guidance produces little or no qpf response across our
area Thu afternoon. Pops will be limited to a slight chance across
roughly the southern half of the area (closer to the departing
frontal zone). Temps will generally remain close to normal, perhaps
a degree or two above, through the period.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 210 PM Monday: A deep SW flow out of the Gulf will develop
Thursday night and persist into the weekend. The persistent upper
level closed low and trough over eastern Canada will rotate and
surge a bit further south during the weekend with axis roughly along
the East Coast. A surface cold front will be pushed south with
moderately strong high pressure dropping down from the western Great
Lakes. This cold front will be the focus of more widespread
convection as it reaches our region late Saturday night and Sunday
morning. If this scenario occurs with front arriving in the cooler
part of the day, this should prevent stronger convection. Of course,
this is nearly a week away and timing of frontal passage could speed
up or slow down. Some strong convection ahead of the cold front may
reach the NC mountains Saturday evening before weakening Saturday
night. Late Saturday is the best chance of severe with prefrontal
forcing and effects of convective generation from diurnal max
heating. Drier air should filter in from the north by late Sunday
night. The front should stall out over Florida to start the upcoming
week with drier weather for at least a couple of days.

Max temps are forecast to be near normal and Min Temps forecast to
be about 5 degrees above normal due to the cloud cover and higher
moisture level preventing radiational cooling.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Guidance all still has convection blossoming
across the Blue Ridge in the next couple of hours and spreading east
across the area through the afternoon/evening. Have timed TEMPO TSRA
as close as possible, including VRB gusty winds as that is the main
threat in any strong/severe storms. Generally VFR through the
evening except in any TSRA, but with cigs becoming BKN-OVC 5-7kft.
could see some MVFR cigs/vsby in the predawn hours on Tuesday.
Introduced another PROB30 at most sites starting 15z Tuesday with
more typical diurnal convection expected.

Outlook: Primarily afternoon and evening TSRA are possible each day,
bringing periodic restrictions. Areas of morning fog and/or low
stratus may potentially develop especially where RA fell the
previous evening. This pattern will continue through at least the
end of the work week.

Confidence Table...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       High 100%     High  96%     High  83%     High  88%
KGSP       High 100%     High 100%     Med   78%     High  83%
KAVL       High  98%     High  89%     High  86%     High  91%
KHKY       High 100%     High 100%     High  80%     High  98%
KGMU       High 100%     High  96%     Med   76%     High  84%
KAND       High 100%     High  97%     High  94%     High  88%

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...DEO
NEAR TERM...TDP/Wimberley
SHORT TERM...JDL
LONG TERM...DEO
AVIATION...TDP

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
319 PM EDT Mon May 29 2017

GAZ017-018-026-028-029-NCZ068>072-082-SCZ001>014-019-301930-
Habersham-Stephens-Franklin-Hart-Elbert-Cleveland-Lincoln-Gaston-
Mecklenburg-Cabarrus-Union-Oconee Mountains-Pickens Mountains-
Greenville Mountains-Greater Oconee-Greater Pickens-
Greater Greenville-Spartanburg-Cherokee-York-Anderson-Abbeville-
Laurens-Chester-Greenwood-
319 PM EDT Mon May 29 2017

...SEVERE THUNDERSTORM WATCH 298 IN EFFECT UNTIL 9 PM EDT THIS
EVENING...

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

.DAY ONE...This Afternoon and Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Severe Thunderstorm Watch.

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

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

.SPOTTER INFORMATION STATEMENT...

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

GAZ010-NCZ033-035>037-048>053-056>059-062>065-501>510-301930-
Rabun-Avery-Alexander-Iredell-Davie-Madison-Yancey-Mitchell-Swain-
Haywood-Buncombe-Catawba-Rowan-Graham-Northern Jackson-Macon-
Southern Jackson-Transylvania-Henderson-Caldwell Mountains-
Greater Caldwell-Burke Mountains-Greater Burke-McDowell Mountains-
Eastern McDowell-Rutherford Mountains-Greater Rutherford-
Polk Mountains-Eastern Polk-
319 PM EDT Mon May 29 2017

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

.DAY ONE...This Afternoon and Tonight.

Coverage of showers and thunderstorms will continue to increase
across the area into the evening hours. A few of the storms may
become severe with damaging winds and large hail. A severe storm
could develop over any location, but the greatest threat will be
across the Piedmont.

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

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

.SPOTTER INFORMATION STATEMENT...

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

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