Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 202245

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
645 PM EDT Sun Jun 20 2021

Tropical Depression Claudette will track east of the area through
the evening and bring periods of heavy rain showers and
thunderstorms. A relative drying period is in store Monday, before a
cold front brings showers and storms back to the region on Tuesday.
Drier and cooler weather is on tap Wednesday through Friday.


As of 630 PM EDT Sunday: Center of TD Claudette is currently over
western South Carolina, just south of the GSP area. East side of
Claudette is continuing to draw moisture northward and support
convection east of the region as the center continues to push
eastward. Scattered showers and thunderstorms will continue through
the evening as a result, primarily in the extreme southeastern tier.
A small chance of a brief tornado will accompany these storms, and
radar will be closely watched for any signs of rotation, but that
threat is quickly diminishing with each radar scan. As Claudette
travels eastward, showers and thunder will travel eastward with it,
with heavy showers ending by 9pm or so this evening, and a few light
and widely scattered showers possible until early Monday morning.
Extensive moisture from the passage of Claudette will leave behind
very moist low-levels, with patchy fog and low clouds likely in most
areas through Monday morning.

Temperatures will remain mild overnight, with lows in the upper 60s
to near 70. Things warming some with clearing behind Claudette, with
values in the 80s and low 90s for highs on Monday. A few showers may
enter the TN border by the very end of the period, ahead of an
incoming cold front, but most locations will be dry for the day
after Fathers Day.


As of 1245 PM Sunday...A fairly sharp and non-seasonal upper level
trof will continue to advance toward the FA early Tue. This trof
will support an active cold front crossing east thru the day and
bring a good chance of convective activity. The latest guidance
continues to show limited sbCAPE, but a decent measure of muCAPE
developing ahead of the llvl convg zone. Meanwhile, while eff-shear
is progged to reach 30 kts per the NAM and arnd 40 kts seen on the
GFS. The op models have come into better agreement with the timing
of the FROPA, which looks to bisect the FA arnd 18z. Upper and
mid-level clouds could hamper strong convec development, but upper
forcing and diff heating may allow upper instability to be realized.
Thus, the area will be under the gun for strong to possibly severe
tstms with some organization possible through the afternoon
period...mainly east of the mtns. The front crosses east Tue night,
while a 1023mb sfc high centers across the OH Valley. This high will
bring in a modest cP airmass mix and keep the atmos mostly dry and
cooler than normal by abt 10 degrees Wed afternoon. Min temps thru
the period will begin a little abv normal Mon night due to
widespread cloudiness, then drop abt 5 degrees below normal Tue
night as the new airmass mixes in from the northeast.


As of 140 PM Sunday...The ext range continues to look unseasonably
cool and mostly dry early on. A modified cP sfc high and a broad ern
CONUS trof will support llvl synoptic winds aligned ne/ly Thu
becoming s/ly by Sat. This will keep a lower theta/e airmass in
place and hold max temps down by a few cats Thu before reaching near
normal levels by Sat. All in a all, a nice period for late June.
Have maintained a low chance of showers and general tstms Fri as a
developing warm front approaches the FA from the southwest. By Sat,
the front will have more llvl moisture to work with and isent lift
increases, so PoPs have been adj up to high chance across the
non/mtns and more numerous activity across the mtns, where the best
lift/moisture interaction looks to occur.


At KCLT and elsewhere: As TD Claudette moves eastward, main area of
thunder has left most locations and for the most part, shouldn`t
affect the terminals, so any TS mention will be taken out in the 00Z
TAF update at all sites. Winds at the surface will vary through the
evening depending on where in relation to the center of Claudette a
location is, with speeds of 5 to 10 kts and gusts to 15. Very moist
tropical airmass is expected to leave behind fog and low ceilings
tonight and tomorrow morning at all TAF sites, with possible IFR
visibility and LIFR ceilings. Clouds should scatter out during the
mid-morning hours Monday, which allows for VFR conditions to prevail
during the back-end of the TAF period.

Outlook: Restrictions associated with Claudette will improve as the
center of the storm moves east on Monday. An additional threat of
restrictions exists Tuesday and Tuesday night with a cold front
entering from the northwest. Drier weather should return to the
region for Wednesday and Thursday.

Confidence Table...

            22-04Z        04-10Z        10-16Z        16-18Z
KCLT       High  82%     Low   57%     Med   62%     High 100%
KGSP       High  80%     Med   65%     Low   47%     High 100%
KAVL       High 100%     Low   52%     Low   57%     High 100%
KHKY       Med   75%     Low   45%     Low   55%     High 100%
KGMU       High  80%     High  80%     Low   42%     High 100%
KAND       Med   77%     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 are available at
the following link:




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