Severe Thunderstorm Warning 134, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
649 AM EDT Fri May 29 2020

.SYNOPSIS...
Warm and moist southerly flow will continue across the region today
ahead of a developing cold front. The front will move into the area
Saturday and track southeast through early Sunday. Dry and a little
cooler air will mix in from the northwest Sunday through the early
part of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 645 am Friday: Spotty convection, primarily showers continue
across the area this morning, along with some patchy dense fog. An
SPS was issued earlier to highlight the latter. Otherwise, the
daylight hours offer the potential for multiple rounds of
scattered/perhaps numerous convective coverage, as height falls
impact the area from the west. High res guidance continues to ramp
up activity within unstable/ confluent axis across the Piedmont
later today...although the latest runs of the HRRR are trending
toward delaying this initiation to more of an early afternoon than a
mid/late morning event. Nevertheless, pops will first ramp up in
areas east of I-85 from mid-morning on. Meanwhile, once the morning
valley fog/low status burns off, the high terrain should become
moderately unstable by early afternoon, allowing scattered deep
convection to fire near the Blue Ridge and push steadily east.
Finally, a cold front is forecast to move into the southern
Appalachians by the end of the day, providing yet another focus for
scattered/numerous convection. Improving deep layer shear, to the
tune of 30-35 kts thanks to accelerating mid-level flow will yield
improved chances for organized convection, with a few storms likely
producing isolated large hail and damaging downbursts. Increased
cell motion should preclude a substantial excessive rainfall threat,
although potential cell training will nevertheless result in a
continued non-zero risk for localized flash flooding. Max temps
should be very similar to yesterday's readings, or right around
climo.

The convective potential will persist into the evening hours as
broad frontal zone sags through the area. However, with deeper
moisture expected to be shunted east of the area, and waning
instability, coverage and intensity of convection should steadily
wane into the overnight hours, with only slight chance pops
appearing warranted from around 06Z on. Min temps will remain above
normal.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 210 AM EDT Friday: The upper pattern remains cyclonic over the
short term period, altho the trof axis will shift east by mid-day
Sat and leave the fcst area under general subsidence. Meanwhile, a
cold front will continue to work across the ern half of the FA
during the early afternoon. Model soundings have different ideas
with the amt of destabilization, with the 00z GFS low-end as it has
a much stronger h65 subs inversion. The NAM on the other hand has
abt 1300 J/kg of sbCAPE with the cap broken by the frontal forcing.
Will expect thunder as a FROPA during peak heating this time of year
is generally always stormy. Some of these storms could become stg
and possibly svr, however with the instability uncertainty, the SPC
doesn/t even have general thunder mention for our area. High
rainfall rates are possible too and with elevated antecedent
conds...isol hydro issue could develop. The front pushes off to the
east Sat evening and strong hipres will ridge in from the NW. This
will bring deeply dry air and cooler cP air mixing into the FA thru
the period. So...after high temps right arnd normal Sat, highs will
drop abt 5 degrees F on Sun. The same trend will follow min temps
Sat/Sun nights.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 225 AM EDT Friday: No sigfnt changes were made to the going
fcst. The latest model runs still agree with a broad ulvl trof
encompassing the region Mon as a modest PFJ aligns se/ly across the
Mid-Atl. This config will keep the trof axis offshore and allow
for general subs across the FA thru Tue. A stg 1026 mb sfc high
will track from the Glakes region to off the Carolina coast by
Tue afternoon, which will keep the region dry and temps a little
below normal Mon/Tue. By Tue night...the sfc high center builds
east into the Atl which will allow a good return flow of GOM
moisture to the the wrn zones, mainly the mtns, both Wed and
Thu. Expect diurnally driven isol/sct showers and thunderstorms
over those areas each afternoon as upper forcing and deep
instability remain low-end. Max and min temps will increase a
little each day. Highs on Wed will reach a cat or so abv normal,
while highs Thu will likely push 90 F outside the mtns and m80s
across the mtn valleys.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: The aviation picture is a bit of a mess this
morning, with several sites (KAVL/KGSP/KHKY) seeing at least
periodic LIFR/VLIFR conditions, while the other TAF sites have
generally been VFR all morning. This is expected to change at KCLT,
where IFR cigs appear poised to overspread the terminal for a couple
of hours later this morning. Meanwhile, flt restrictions appear less
likely at KAND/KGMU...and a VFR forecast is carried at those sites.
Most sites should be VFR by late morning or so.

Otherwise, confidence is rather low regarding convective trends
throughout the day, as model guidance does not appear to have the
best handle on the situation. Isolated/widely SCT showers are
already occurring this morning, and VCSH is carried at most sites to
handle that. However, it's not clear to what degree morning showers
and clouds are going to limit afternoon instability, and high
resolution models are kind of all over the place regarding timing
and placement of convection throughout the next 18 or so hours. As
such, did not feel comfortable including a convective tempo at any
site, and instead opted for VCTS (VCSH at KCLT) throughout the
afternoon and evening, with Prob30s for -TSRA from 21-03Z at most
sites.

Confidence regarding cig/visby trends tonight/early Saturday is also
low, but generally lowering cigs and somewhat deteriorating visby
appear likely, and this is reflected in the TAFs. Otherwise,
generally light/vrbl winds will become SW and increase to 5-10 kts
during the afternoon.

Outlook: One more day of active weather is expected Saturday before
dry high pressure builds into the area on Sunday and continues
through at least early next week.

Confidence Table...

            10-16Z        16-22Z        22-04Z        04-06Z
KCLT       Med   72%     High  95%     High 100%     High  91%
KGSP       Med   73%     High 100%     High 100%     High  97%
KAVL       Low   49%     High 100%     High 100%     High  84%
KHKY       Low   29%     High  95%     High 100%     High  94%
KGMU       Med   75%     High 100%     High 100%     High  97%
KAND       Med   69%     High 100%     High 100%     High  97%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables 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...JDL
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
425 AM EDT Fri May 29 2020

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-300830-
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 NC-
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-Union SC-Chester-Greenwood-
425 AM EDT Fri May 29 2020

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

.DAY ONE...Today and tonight.

Scattered to numerous thunderstorms will develop this afternoon and
linger into the evening hours. A few of these storms could become
quite strong to severe with the main threats being damaging winds and
large hail. Cloud to ground lightning will also be probable.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information about
observed severe weather to the NWS while following all local, state,
and CDC guidelines.

Krentz

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1141 AM EDT Fri May 29 2020

NCZ070-071-082-SCZ009-291615-
Gaston NC-Union NC-Mecklenburg NC-York SC-
1141 AM EDT Fri May 29 2020

...A STRONG THUNDERSTORM WILL IMPACT MECKLENBURG...SOUTHEASTERN
GASTON...NORTHWESTERN UNION AND NORTHEASTERN YORK COUNTIES UNTIL 1215
PM EDT...

At 1141 AM EDT, Doppler radar was tracking a strong thunderstorm 7
miles southwest of Uptown Charlotte, or near Southwest Charlotte,
moving east at 25 mph.

Locations to be impacted include...
Uptown Charlotte, Rock Hill, Gastonia, Central Charlotte, South
Charlotte, Northeast Charlotte, Southwest Charlotte, East Charlotte,
Northwest Charlotte and Matthews.

Wind gusts up to 55 mph and dime size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

Doppler radar indicates weak rotation with this storm. Spin-up of a
very brief, weak tornado cannot be ruled out. Be prepared to take
immediate action if a tornado is sighted or a Tornado Warning is
issued.

&&

LAT...LON 3506 8053 3500 8084 3508 8091 3503 8090
      3501 8091 3500 8090 3496 8109 3520 8119
      3538 8074
TIME...MOT...LOC 1541Z 253DEG 23KT 3514 8093

12

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1207 PM EDT Fri May 29 2020

SCZ009-014-291630-
York SC-Chester SC-
1207 PM EDT Fri May 29 2020

...A CLUSTER OF THUNDERSTORMS WILL IMPACT EASTERN CHESTER AND
SOUTHEASTERN YORK COUNTIES UNTIL 1230 PM EDT...

At 1207 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 7 miles southeast of
Rock Hill to 8 miles southeast of Chester, and moving northeast at 50
mph.

Locations to be impacted include...
Great Falls, Fort Lawn, Richburg, Catawba, Blackstock, Fishing Creek
Reservoir, Cornwell and Edgemoor.

Wind gusts up to 45 mph and pea size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

Torrential rainfall may flood areas with poor drainage, such as
ditches and underpasses. Avoid these areas and do not cross flooded
roads. Water levels of small streams may also rise rapidly. Seek
higher ground if threatened by flood waters.

These storms may intensify, so be certain to monitor local radio and
tv stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3467 8089 3464 8090 3460 8089 3456 8087
      3455 8088 3454 8093 3457 8130 3482 8108
      3486 8088 3486 8087 3484 8087 3483 8090
      3479 8088 3475 8088 3470 8086
TIME...MOT...LOC 1607Z 229DEG 42KT 3487 8092 3461 8112

12

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1213 PM EDT Fri May 29 2020

NCZ071-082-291645-
Union NC-Mecklenburg NC-
1213 PM EDT Fri May 29 2020

...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN MECKLENBURG AND
NORTHWESTERN UNION COUNTIES UNTIL 1245 PM EDT...

At 1213 PM EDT, Doppler radar was tracking a strong thunderstorm near
Indian Land, or near Marvin, moving northeast at 30 mph.

Locations to be impacted include...
South Charlotte, Matthews, Indian Trail, Weddington, Stallings,
Wesley Chapel, Waxhaw, Lake Park, Mineral Springs and Marvin.

Wind gusts up to 55 mph and dime size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

The combination of gusty winds and saturated soil conditions will
cause scattered trees and power lines to fall. Seek shelter inside an
interior room.

Torrential rainfall may flood areas with poor drainage, such as
ditches and underpasses. Avoid these areas and do not cross flooded
roads. Water levels of small streams may also rise rapidly. Seek
higher ground if threatened by flood waters.

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3494 8060 3490 8079 3494 8078 3506 8089
      3516 8065
TIME...MOT...LOC 1613Z 245DEG 26KT 3498 8080

12

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