Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
655 AM EDT Thu May 31 2018

.SYNOPSIS...
A moist airmass will persist today into Friday, with a couple of
rounds of thunderstorms crossing the region from the west each
afternoon and evening. Slightly drier air will work in from the west
on Saturday, but with a brief return of moisture by late weekend.
Better drying will arrive behind a passing cold front in the early
to middle part of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...

...FLASH FLOOD WATCH FOR THE MOUNTAINS AND NC FOOTHILLS REMAINS
IN EFFECT THROUGH FRIDAY MORNING...

As of 655 AM EDT Thursday: Main update for 12Z TAF issuance
along with minor tweaks to temperatures as the rest of the near
term forecast remains on track. Given excessive rainfall over
the past two weeks, ongoing flooding concerns, and the
persistent unsettled weather pattern with scattered showers and
isolated thunderstorms expected today and tonight, the Flash
Flood Watch has been extended through Friday morning for the
mountains and NC foothills.

Latest radar imagery depicts isolated continuing to move across the
area this morning, though coverage has decreased from just a few
hours ago. Unfortunately, the relief from unsettled weather remains
out of sight through at least the near term forecast period. As an
upper Atlantic ridge remains in place just off the eastern seaboard
(which will slightly weaken today), a series of shortwave troughs,
which includes the remnants of Alberto, are expected to propagate
east-northeastward across the Great Lakes region and northward today
and tonight. One of these waves will stretch southward, bringing
additional lift and the potential for convection to move across the
mountains late afternoon/early evening, waning as it progresses
eastward tonight. Additionally, with high pressure centered over
northern Mexico as well, the infiltration of moisture from the GOM
will continue to stream in, but from more of a westerly fetch as mid-
level flow veers - across the lower MS Valley and into the
Southeast. This will allow for PWATs to drop from the nearly 2
inches we've seen down to 1 to 1.5 inches (at most). Even then,
plenty of available moisture remains in place. Overall, though a
lull in precip will likely occur later this morning and into the
early afternoon hours, typical diurnal convection is expected later
this afternoon, especially across the mountains. In addition, with
the features mentioned above, latest guidance continues to highlight
the potential for a gradually organizing line of showers and
thunderstorms to move in from the west this evening, and waning as
it nears the I-77 corridor tonight. Though most of the enhanced risk
for severe weather will remain west of the area, some storms
could become severe as the NC mountains currently are outlined
in a Marginal Risk for SPCs Day 1 Convective Outlook.

Though the potential for higher rainfall rates from heavier
downpours and/or stronger storms will be less widespread than we saw
the past few days, the potential will still be there today and
tonight with any activity. Looking at areas from the northeast GA
mountains, northeast up through to Avery/Caldwell counties (NC), the
amount of rainfall that has fallen within the past two weeks ranges
anywhere from 6 inches to 18 inches (atleast). As was also mentioned
around the middle of the month, Asheville already broke the record
for the wettest month of May on record (the previous record being in
2009). Needless to say, the grounds are beyond saturated, flooding
is ongoing in some locations, and the addition of rainfall from any
heavy downpours/strong storms today and tonight will only add to the
problem. Thus, the Flash Flood Watch has been extended through
Friday morning.

Temperatures through the near term will remain just above normal.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
As of 335 AM Thursday: The northern tier system over the Great lakes
will deepen early Friday and bring a fairly prominent shortwave
across the southern Appalachians Friday afternoon. Convection
developing southeast of the Ohio River Valley Friday morning should
make a run southeast and likely survive through at least the
southern Appalachians, if not the whole piedmont. Convection could
be rather strong as the cap will likely break by mid-afternoon and
mid-level flow will increase to 30+ kt. In addition, steep mid-level
lapse rates of 7 to 7.5 deg C/km should strengthen storms over the
Appalachians Friday afternoon and permit then to run well east
through evening. The Marginal risk from SPC for day 2 looks well
placed.

The primary vorticity lobe will move east of the piedmont by
Saturday, but a weak surface boundary will settle southward through
the region. A slight lull in the shower coverage is possible, but
still anticipate scattered shower and thunderstorm coverage Saturday
afternoon given the lingering moist boundary layer. Northern tier
temperatures may cool a category over Friday given the passing front.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 340 AM Thursday: A few weak embedded waves in the developing
northwest flow will follow through the late weekend and these could
drive a low pressure system from the mid MS valley toward the
southern Appalachians. In addition, warm sector instability will
bubble back up and likely be rather robust by Sunday afternoon.
Expect an associated uptick in PoPs through Sunday.

Deep layer northwesterly will get reestablished on Monday and
persist through mid-week. There is some potential for shortwave
energy to pivot around the New England low pressure system and reach
the southern Appalachians on Tuesday. However, any shortwaves moving
through the region aloft will be limited in both forcing and
moisture. A backdoor front will likely arrive sometime midweek.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: A mixture of MVFR/IFR prevails across the
area this morning, though a few breaks in the clouds are allowing
for intermittent periods of improvement to VFR at times. With patchy
areas of fog, low cigs, and isolated showers, expect overall
MVFR/IFR to continue over the next few hours. Later this morning,
anticipate a gradual improvement to a mixture of VFR/MVFR, with
passing clouds still SCT/BKN in nature. Anticipate diurnal scattered
showers and thunderstorms this afternoon, with scattered storms
expect to push eastward across the mountains this evening, waning as
they near KCLT tonight. Given the unsettled weather pattern,
VCSH/VCTS/-SHRA/-TSRA activity has been noted by TEMPO/PROB30
groups. A mixture of IFR will be possible with any passing low cigs
and/or heavy downpours. Southwest winds 5 to 10 kts will prevail
through the valid TAF period, with occasional gusts possible in any
stronger storms. Lingering light showers are possible overnight, but
overall expect VFR to prevail, though patchy areas of fog will be
possible towards the end of the valid TAf period.

Outlook: Slightly drier air will filter into the area for the end of
the work week. However, scattered afternoon/evening showers and
thunderstorms, along with possible morning fog and/or low cigs are
expected each day through early next week.

Confidence Table...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High  93%     High 100%     High 100%     High 100%
KAVL       Med   78%     High 100%     High 100%     High 100%
KHKY       High  85%     High 100%     High 100%     High 100%
KGMU       High  93%     High 100%     High 100%     High 100%
KAND       High  93%     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...Flash Flood Watch through Friday morning for GAZ010-017.
NC...Flash Flood Watch through Friday morning for NCZ033-048>053-
     058-059-062>065-501>510.
SC...Flash Flood Watch through Friday morning for SCZ001>003.

&&

SYNOPSIS...HG
NEAR TERM...SGL
SHORT TERM...HG
LONG TERM...HG
AVIATION...SGL

Hazardous Weather Outlook...CORRECTED
National Weather Service Greenville-Spartanburg SC
522 AM EDT Thu May 31 2018

GAZ018-026-028-029-NCZ035>037-056-057-068>072-082-SCZ004>014-019-
010930-
Stephens-Franklin-Hart-Elbert-Alexander-Iredell-Davie-Catawba-Rowan-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union-Greater Oconee-
Greater Pickens-Greater Greenville-Spartanburg-Cherokee-York-
Anderson-Abbeville-Laurens-Chester-Greenwood-
522 AM EDT Thu May 31 2018

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

.DAY ONE...Today and Tonight.

Isolated heavy rain showers will be possible this morning in a few
locations. Scattered showers and thunderstorms will redevelop from
the west this afternoon and evening. Any of these heavy downpours
will have the potential to produce isolated flooding, especially if
several showers affect the same location. Any afternoon and evening
thunderstorms may produce cloud-to-ground lighting, briefly gusty
winds, pea-size hail, and very heavy rainfall. Saturated soil
conditions could lead to a few trees getting knocked down by the
gusty winds.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

..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.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

GAZ010-017-NCZ033-048>053-058-059-062>065-501>510-SCZ001>003-010930-
Rabun-Habersham-Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-
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-
Oconee Mountains-Pickens Mountains-Greenville Mountains-
522 AM EDT Thu May 31 2018

...FLASH FLOOD WATCH IN EFFECT THROUGH FRIDAY MORNING...

This Hazardous Weather Outlook is for the mountains of northeast
Georgia, western North Carolina, and Upstate South Carolina, as well
as the North Carolina foothills.

.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.

Numerous showers and thunderstorms will redevelop from the west this
afternoon and evening. Any of these thunderstorms may produce cloud-
to-ground lighting, briefly gusty winds, pea-size hail, and very
heavy rainfall. Saturated soil conditions could lead to a several
trees getting knocked down by the gusty winds.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

..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.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1243 PM EDT THU MAY 31 2018

NCZ065-509-510-SCZ003-007-311715-
Henderson NC-Polk Mountains NC-Eastern Polk NC-
Greenville Mountains SC-Spartanburg SC-
1243 PM EDT THU MAY 31 2018

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
SOUTHEASTERN HENDERSON...SOUTHWESTERN POLK...NORTHEASTERN GREENVILLE
AND NORTHWESTERN SPARTANBURG COUNTIES UNTIL 115 PM EDT...

At 1243 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 7 miles south of Hendersonville, or near Flat Rock,
moving southeast at 15 mph.

Locations to be impacted include...
Columbus, Hendersonville, Flat Rock, Landrum, Tryon, Saluda,
Tigerville, Gowensville, North Saluda Reservoir and Tuxedo.

In addition to intense lightning, wind gusts up to 40 mph and very
heavy rainfall rates up to 2 inches per hour will be possible in
these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3521 8211 3506 8224 3502 8236 3518 8256
      3533 8244
TIME...MOT...LOC 1643Z 303DEG 14KT 3522 8243

TDP

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
106 PM EDT THU MAY 31 2018

NCZ051-058-311730-
Graham NC-Swain NC-
106 PM EDT THU MAY 31 2018

...A CLUSTER OF THUNDERSTORMS WITH INTENSE LIGHTNING WILL IMPACT
SOUTHWESTERN SWAIN AND GRAHAM COUNTIES UNTIL 130 PM EDT...

At 106 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms with intense lightning along a line extending from
14 miles southeast of Maryville to 12 miles northwest of
Robbinsville, and moving southeast at 20 mph.

Locations to be impacted include...
Robbinsville, Town Of Santeetlah, Smoky Mountains-Fontana Area, Lake
Santeetlah, Fontana Lake, Fontana Village, Smoky Mountains-Twentymile
Creek, Smoky Mountains-Clingmans Dome, Smoky Mountains-Deep Creek and
Stecoah.

In addition to intense lightning, wind gusts up to 40 mph, pea size
hail and very heavy rainfall rates up to 2 inches per hour will be
possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with these storms. If outdoors, try
to get indoors or into a hard topped vehicle. Otherwise, stay away
from open areas and isolated high objects such as trees. When
indoors, stay away from windows and doors and avoid using wired
electronic devices. Do not take a shower or bath. Try to unplug
unnecessary appliances before the storms approach.

&&

LAT...LON 3537 8401 3541 8402 3546 8396 3547 8392
      3552 8388 3553 8382 3556 8377 3557 8363
      3558 8360 3556 8358 3556 8350 3552 8341
      3524 8375 3526 8379 3525 8385 3522 8396
      3531 8404 3535 8404
TIME...MOT...LOC 1706Z 313DEG 16KT 3561 8377 3542 8400

TDP

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
108 PM EDT THU MAY 31 2018

NCZ033-501-502-311745-
Caldwell Mountains NC-Greater Caldwell NC-Avery NC-
108 PM EDT THU MAY 31 2018

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT CALDWELL
AND SOUTHEASTERN AVERY COUNTIES UNTIL 145 PM EDT...

At 107 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 8 miles southwest of Blowing Rock, or 7 miles east
of B.R. Parkway-Linville Falls To Grandfather, moving southeast at 15
mph.

Locations to be impacted include...
Lenoir, Gamewell, Edgemont, Globe, Collettsville, Patterson and
Upton.

In addition to intense lightning, wind gusts up to 40 mph, pea size
hail and very heavy rainfall rates up to 2 inches per hour will be
possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3601 8143 3581 8159 3582 8160 3582 8162
      3585 8164 3588 8171 3592 8175 3593 8178
      3595 8178 3595 8180 3597 8182 3598 8186
      3612 8176 3612 8172
TIME...MOT...LOC 1707Z 303DEG 13KT 3602 8174

TDP