Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1049 AM EDT Tue May 23 2017

.SYNOPSIS...
A train of Gulf low pressure systems will track through our
area along a stalled front through tonight. As the front moves
southeast, a broad area of showers and storms crosses our area
Wednesday ahead of a closed upper low pressure. Expect temperatures
to be below normal until the deep upper trough moves out before the
start of the weekend. A drying trend will begin by the end of the
work week and continue until the end of the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1030 AM EDT: KGSP base reflectivity shows a boundary drifting
southeast across the foothills of the western Carolinas this morning
but with widespread moderate precipitation continuing to the
southeast. Meanwhile, weak surface waves continue to slide northeast
along the boundary to aid shower coverage while a more potent
wave was moving northeast into southwest GA late this morning.
Very high coverage of at least light rainfall should continue
for most of the area, but the focus of the heavy rainfall, and
the better thunderstorm threat, will be over the piedmont as
the wave approaches through the afternoon hours. No changes are
planned to the Flash Flood Watch area at present.

The guidance remains in fairly good agreement that the main wave
will mostly move out tonight (generally after 00z), with a bit of a
lull in the activity for the end of the near-term period. Precip
associated with the approaching upper trough will move in as we
begin the short term. As for continued convective potential, the
widespread rain/clouds will keep temperatures down (highs today
should be about 10 degrees below seasonal norms) and limit
instability, but some areas across southern zones could see up to
between 500-1000J/kg during peak heating. The current Marginal Risk
in extreme southern zones seems reasonable, especially with some
deep-layer shear coming across with the upper jet. Profiles remain
too tropical for much in the way of a hail threat, so if anything it
would most likely be some gusty winds.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 300 AM Tue: A mature low pressure system will remain
generally over the middle Mississippi and lower Ohio valleys Wed
and early Thu. Its warm conveyor belt will bring abundant moisture
flux and isentropic upglide atop our area Wed, reactivating the
stalled boundary as a warm front once again, which continues
to push north Wed night. A portion of the area thus will see
warm-sector conditions, featuring subtropical moisture and an
uptick in instability. Strong upper level winds will generate
appreciable deep-layer shear, and t-storms may organize into linear
segments. The cold front will approach the area through the morning,
pushing in by late afternoon. With a shortwave moving northward as
it rounds the upper low, both NAM and GFS generate a mesoscale sfc
wave along the front. This could significantly increase the severe
wind threat by strengthening or backing the low level winds. Note
SPC has now expanded the marginal risk to most of the CWFA for
Day 2, and the slight risk to a portion of the Upstate southeast
of I-85.

Furthermore, both NAM/GFS develop an area of heavy rain in response
to the enhanced convergence with their frontal waves. Unfortunately
they do not agree on when this occurs, though they both suggest the
mountain/foothill zones are the most likely locations to experience
the enhanced precip. Confidence is high on a wave developing,
but confidence is low on the placement. We have opted to give the
next shift a chance to evaluate the need for a flash flood watch
for Wednesday, as well as being able to better judge the areal
extent thereof.

The thunderstorm threat will diminish Wed night following the
front, but moisture remains plentiful in its wake. The upper
low itself will drift overhead at that time, which warrants
a continuation of PoP overnight; westerly upslope flow makes
this particularly necessary near the Tenn border. Excellent
lapse rates and diurnal warming on Thursday bring back enough
instability to expect increasing shower coverage. With over 500
J/kg of CAPE progged over portions of WNC and the eastern Upstate,
thunderstorms producing small or perhaps even marginally severe
hail will be possible. Deep mixing and cold advective flow will
produce somewhat gusty winds. Precip chances finally taper off
Thu night, though continued upsloping may allow some lingering
showers in the mountains.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 150 AM Tuesday:  Starting at 12Z Friday weak high pressure
will be in control of our weather to start the weekend as the upper
low crosses New England and the next systems gather over the Rockies
and Plains States. The next closed upper low affecting our weather
will rotate over the North Dakota and Canadian border Saturday and
drop down to Wisconsin Sunday night. This feature will be the
driving force for shortwaves moving from the Plains States to the
Appalachians to start next week. The intensity of the convection
affecting our weather will have much to do with the timing of the
associated cold front. The GFS has the front crossing our region
late Monday which may be near peak daily heating for much of the
area. Therefore, instability would be greater with this model
solution. However, the ECMWF currently has the front crossing Sunday
night which would result in lower chances of storms due to less
instability. There would be less cooling with this upper system
since models are consistent in taking the upper system NE to eastern
Canada once it reaches the Great Lakes. At this point, Day 7 of the
current forecast has much uncertainty due to lack of model agreement
on how quickly the cold front crosses our region. There is some
agreement that by 12Z Tuesday of next week that drying will take
place as high pressure moves in behind the front.

Temperatures will be near or just below normal Friday as the upper
low moves away then temperatures a little above normal through the
rest of the medium range.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: TAFs remain complicated late this morning
with abundant moisture and rain supporting widespread IFR, but
lingering pockets of VFR slipping into obs at times. As additional
SHRA overspreads the region, IFR cigs should prevail, with some
improvement to lower-end MVFR possible this afternoon. Could also
see some isolated TSRA for Upstate TAFs and KCLT, but will only
include afternoon TEMPOs for KAND and KCLT at this time. Timing
difficult to narrow down as embedded TS within the larger precip
shield could continue off and on through the day. SHRA moves out
late this afternoon/early evening, but restrictions remain and with
plentiful low-level moisture ahead of the next system, should see
widespread IFR to LIFR again Wednesday morning. Winds still forecast
to be all over the place and truly VRB as this will depend on track
of surface low across the area. For KCLT, will generally keep
conditions ENE before turning more NW later this afternoon, and then
back to NE by 00z.

Outlook: Periods of showers and thunderstorms with associated
restrictions will continue off and on through Thursday. Drying is
expected to finally occur through the end of the week.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       Med   73%     High  90%     Med   74%     Med   69%
KGSP       Med   78%     Med   69%     Med   72%     Low   55%
KAVL       High  83%     Med   64%     Med   65%     High  85%
KHKY       High  80%     High  82%     Med   76%     Med   76%
KGMU       Med   78%     Med   69%     Med   75%     Med   79%
KAND       High  91%     Med   75%     High  82%     Med   79%

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...Flash Flood Watch through late tonight for GAZ018-026-028-029.
NC...Flash Flood Watch through late tonight for NCZ035>037-056-057-
     064-065-068>072-082-501>510.
SC...Flash Flood Watch through late tonight for SCZ001>014-019.

&&

SYNOPSIS...DEO
NEAR TERM...HG/TDP
SHORT TERM...Wimberley
LONG TERM...DEO
AVIATION...HG/TDP

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
357 AM EDT Tue May 23 2017

GAZ026-028-029-SCZ010>012-019-240800-
Franklin-Hart-Elbert-Anderson-Abbeville-Laurens-Greenwood-
357 AM EDT Tue May 23 2017

...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...

This Hazardous Weather Outlook is for the Lakelands of northeast
Georgia and southern upstate South Carolina.

.DAY ONE...Today and Tonight.

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

   Flash Flood Watch.

Also, thunderstorms are in the forecast today. In addition to the
usual threat of cloud-to-ground lightning, one or two of the
stronger storms will be capable of damaging wind gusts.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

..Wednesday...Severe weather with flash flooding possible. As a warm
front lifts northward, unstable subtropical air will push into the
area, leading to another round of thunderstorms. Strong winds in the
upper atmosphere may allow these storms to organize and produce
severe weather, in the form of damaging winds and quarter-size hail.
Intense rainfall may cause localized flash flooding, where soils
remain saturated from rainfall earlier in the week.
..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.
..Monday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ018-NCZ035>037-056-057-064-065-068>072-082-501>510-SCZ001>009-013-
014-240800-
Stephens-Alexander-Iredell-Davie-Catawba-Rowan-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-Chester-
357 AM EDT Tue May 23 2017

...FLASH FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...

This Hazardous Weather Outlook is for the foothills and Piedmont
areas of North and South Carolina, plus northeast Georgia.

.DAY ONE...Today and Tonight.

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

   Flash Flood Watch.

Also, thunderstorms are in the forecast today. Cloud-to-ground
lightning will be a threat with these storms, in addition to the
flash flooding potential.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

..Wednesday...Severe weather with flash flooding possible. As a warm
front lifts northward, unstable subtropical air will push into the
area, leading to another round of thunderstorms. Strong winds in the
upper atmosphere may allow a few of these storms to become severe,
producing damaging winds and quarter-size hail. Intense rainfall may
cause localized flash flooding, where soils remain saturated from
rainfall earlier in the week.
..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.
..Monday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-NCZ033-048>053-058-059-062-063-240800-
Rabun-Habersham-Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-
Graham-Northern Jackson-Macon-Southern Jackson-
357 AM EDT Tue May 23 2017

This Hazardous Weather Outlook is for the mountains of northeast
Georgia and western North Carolina.

.DAY ONE...Today and Tonight.

Thunderstorms are in the forecast today. Cloud-to-ground lightning
and heavy rain will be the primary threats with these storms. Flooding
could develop on small creeks and streams, in poorly drained areas,
or in areas that see multiple rounds of heavy rainfall.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

..Wednesday...Severe weather with flash flooding possible. As a warm
front lifts northward, unstable subtropical air will push into the
area, leading to another round of thunderstorms. Strong winds in the
upper atmosphere may allow a few of these storms to become severe,
producing damaging winds and quarter-size hail. Intense rainfall may
cause localized flash flooding, where soils remain saturated from
rainfall earlier in the week.
..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.
..Monday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Wimberley

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
753 AM EDT TUE MAY 23 2017

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0700 AM     NON-TSTM WND DMG 3 SSE CHARLOTTE         35.16N 80.81W
05/23/2017                   MECKLENBURG        NC   BROADCAST MEDIA

            TREE DOWN ON ARBOR WAY.

&&

LVISIN

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
121 PM EDT TUE MAY 23 2017

NCZ082-231745-
Union NC-
121 PM EDT TUE MAY 23 2017

...GUSTY AND HEAVY SHOWERS WILL IMPACT SOUTHEASTERN UNION COUNTY
UNTIL 145 PM EDT...

At 119 PM EDT, Doppler radar was tracking robust showers 7 miles
southwest of Monroe, or 4 miles southeast of Mineral Springs, moving
northeast at 20 mph.

Locations to be impacted include...
Monroe, Wingate, Marshville, Sturdivants, Mineral Springs and
Trinity.

Wind gusts up to 40 mph along with a period of heavy rain will be
possible in these areas.

LAT...LON 3482 8032 3481 8049 3482 8050 3482 8062
      3497 8067 3509 8031
TIME...MOT...LOC 1719Z 240DEG 19KT 3490 8062