Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1003 PM EDT Mon Jul 19 2021

.SYNOPSIS...
An upper-level trough of low pressure will remain just west of the
southern Appalachians through Tuesday, while a weak stationary front
remains stalled over the region. The trough will finally move
southeast of the area on Wednesday. Until then, increased clouds and
precipitation chances will keep high temperatures below normal.
Somewhat drier air arrives from the north on Thursday and
temperatures rebound to near-normal or slightly above through late
week.

&&

.NEAR TERM /THROUGH TUESDAY/...
Evening Update...Pockets of moderate to heavy rain showers continue
this evening, mainly across the srn Upstate and NE GA. Expect
an upper trof to tighten overnight and align s/w energy across
the wrn upslope regions, while a modest llvl h92-h85 jet
develops. This will set the stage for deep convective showers
with some thunder potential capable of producing high rainfall
rates beginning generally after 06z and continuing thru
daybreak. Some training and anchoring of cells is likely and
flooding conds shud develop across localized streams as well as
poor drainage areas. The Flash Flood Watch still looks good into
the afternoon period.

As of 205 pm: The latest surface analysis indicates the leading edge
of the weak frontal zone has pushed into the northern tier of SC
counties. The boundary will continue to ooze slowly south across the
area through the period, and continue to be the primary focus of
convective development...although terrain effects will work their
usual magic, while PWATs above 1.75" and a weakly forced environment
acting on modest instability will allow showers to develop just
about anywhere. PoPs therefore ramp up to likely-to-categorical this
afternoon across all areas excepting locations north of the front
(i.e., the northwest NC Piedmont), where chance PoPs should suffice.
As was the deal yesterday afternoon/evening, the potential will
exist for cell training, esp in the vicinity of the frontal zone,
resulting in a continued threat of localized flash flooding.
Meanwhile, thunderstorms will be difficult to come by in the weakly
forced warm/moist environment, and the severe storm threat is
therefore virtually non-existent.

Overnight, an upper low is forecast to take shape across the TN
Valley by daybreak Tue. Most short term guidance sources are
developing a weak surface reflection along the boundary to our
west...most likely in the vicinity of the AL/TN/GA border. This
would act to focus low level convergence across far western portions
of our forecast area, with the addition of a respectably strong (for
the time of year) E/SE upslope flow. Therefore, if any part of the
forecast area stands to see more of an organized heavy rainfall
and/or flash flood threat, it would be our northeast GA and
northwest SC zones. We are currently forecasting around 2 inches in
this area through the period, but locally higher amounts are
likely...possibly much higher amount depending upon terrain
exposure. This area is too small and confidence still too low to
consider a Flash Flood Watch, but this area will need closer
scrutiny as time goes forward. Otherwise, PoPs ramp up to
categorical across the southwest quarter or so of the area between 6
and 12Z...tapering to low chance at best across the northwest NC
Piedmont.

Leading edge of the frontal zone is expected to sag south of the
area by the end of Tuesday, taking what little instability there is
along with it. Nevertheless, moisture will remain abundant over the
forecast area, and numerous to widespread showers ongoing at the
start of the day should persist through at least the morning hours,
with a continued potential for locally heavy/excessive rainfall. Max
temps will again be below normal, perhaps well-below normal where
dense low clouds are more persistent (i.e., the Blue Ridge and SC
foothills.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 230 PM EDT Monday: Tuesday night into Wednesday the trough
axis will remain in place across the CWA, however, PoPs will
gradually decline during this time frame. Models continue showing a
low pressure center breaking off from the trough Tuesday night into
Wednesday and tracking southwest into Texas. The upper-level trough
will track out of the region Wednesday night. The low remains in
Texas as high pressure builds across the Desert Southwest Thursday.
Meanwhile broad troughing remains across the East Coast Thursday
thanks to a large low pressure system in eastern Canada. Moisture
sticks around Tuesday night into Wednesday as the stationary front
remains draped across southern NC and northern SC. PWATs will
continue to hover around 1.5 inches for the mtns and 1.5 to 2.0
inches outside the mtns. The stalled front will lead to southerly
and westerly flow ahead of the frontal boundary with northerly flow
behind it. As a result, diurnal shower and thunderstorm chances
should decrease for the far northeastern zones due to drier air
while scattered diurnal activity looks best across the SC Upstate
and southwest NC mtns on Wednesday. Moisture will gradually decrease
from north to south Wednesday afternoon into Thursday as the
stationary front dissipates. This will allow flow on Thursday to
become mostly westerly and northerly across the CWA leading to
further drying of the lower and mid-levels. In response, PWAT values
should decrease across the northern tier of the forecast area
Thursday. Diurnal shower and thunderstorm chances return Thursday
with the far SW NC mtns and NE GA mtns having the best chance for
PoPs. Highs will gradually increase throughout the short term
period. However, high temps Wednesday will remain a few degrees
below climo, climbing to near or just above climo Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 230 PM EDT Monday: The high pressure system persists out
across the Desert Southwest while low pressure lingers across Texas
for much of the extended forecast period. Broad troughing hangs
around the East Coast Friday into the weekend as a result of large
low pressure systems tracking east across Canada. Lower moisture
content can be expected due to northerly and westerly flow across
the forecast area Friday allowing PWAT values to decrease across the
southern tier. Diurnal shower and thunderstorm chances continue on
Friday with the best chances for PoPs across the mtns. PWATs are
expected to climb back up this weekend into early next week as a
long wave trough digs across the eastern CONUS. A cold front
associated with this trough could track out of the Ohio Valley early
next week approaching the forecast area. This will lead to an uptick
in moisture and PoPs this weekend into early next week. High temps
throughout the extended will be a few degrees above climo.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
At KCLT and Elsewhere: A stationary front will slowly shift south
through the TAF period. Mainly MVFR restrictions at KCLT overnight
and into tomorrow morning as scattered showers and thunderstorms
spread through the area.  With heavier rain showers expected
elsewhere, CIGS may lower to IFR in the hours before daybreak,
lingering through midmorning. VSBYS will also decrease to MVFR or
possibly IFR overnight as well. Expect improvement to MVFR/VFR CIGs
in the afternoon, accompanied by scattered thunderstorms developing
across the Upstate terminals and at KCLT. Winds outside the
mountains will remain weak and northeasterly overnight. At KCLT
winds will shift more northwesterly after 19Z.  Across the
mountains, winds will shift northwesterly by 14Z.

Outlook: The moist, unsettled pattern will continue, with a steady
decrease in shower and thunderstorm activity then expected during
the middle to later part of the week. Overnight/early morning
fog/low stratus will be possible each day.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High  93%     Low   50%     Low   58%     Med   62%
KGSP       High 100%     Low   55%     Med   72%     Med   77%
KAVL       High  84%     High  90%     Low   49%     Low   44%
KHKY       High  93%     Med   66%     High  88%     High  89%
KGMU       High  92%     Med   64%     Med   70%     Med   74%
KAND       High  86%     Med   64%     High  83%     Med   75%

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...Flash Flood Watch through Tuesday afternoon for GAZ010-017-018-
     026.
NC...None.
SC...Flash Flood Watch through Tuesday afternoon for SCZ001-002-004-
     005.

&&

SYNOPSIS...DEO
NEAR TERM...JDL/MPR/SBK
SHORT TERM...AP
LONG TERM...AP
AVIATION...MPR/SBK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1007 PM EDT Mon Jul 19 2021

GAZ028-029-NCZ033-035>037-048>053-056>059-062>065-068>072-082-
501>510-SCZ003-006>014-019-210215-
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-
Greenville Mountains-Greater Greenville-Spartanburg-Cherokee-York-
Anderson-Abbeville-Laurens-Union SC-Chester-Greenwood-
1007 PM EDT Mon Jul 19 2021

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

.DAY ONE...Tonight.

Showers with embedded thunderstorms will continue to across the area
into the overnight. Most of the activity will occur across the
Upstate and northeast Georgia. The main threats, will be cloud to
ground lightning along with heavy downpours possibly leading to
localized minor flooding. Heavier rainfall is expected to develop
across the western Upstate and northeast Georgia overnight.

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

Numerous showers will persist through Tuesday, producing heavy
rainfall throughout the day. A flash flooding threat will remain
throughout the day as rain falls on saturated soils and raised stream
levels already primed by tonight's precipitation.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-SCZ001-002-004-005-210215-
Rabun-Habersham-Stephens-Franklin-Oconee Mountains-Pickens Mountains-
Greater Oconee-Greater Pickens-
1007 PM EDT Mon Jul 19 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH TUESDAY AFTERNOON...

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

.DAY ONE...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.

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

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

 Flash Flood Watch.

.SPOTTER INFORMATION STATEMENT...

None.

Krentz

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
156 AM EDT Tue Jul 20 2021

GAZ010-017-018-026-028-029-NCZ062-SCZ001-002-004-005-010-200800-
Elbert GA-Hart GA-Franklin GA-Rabun GA-Stephens GA-Habersham GA-
Macon NC-Pickens Mountains SC-Greater Pickens SC-Greater Oconee SC-
Anderson SC-Oconee Mountains SC-
156 AM EDT Tue Jul 20 2021

...AN AREA OF HEAVY RAINFALL WILL IMPACT FRANKLIN...STEPHENS...
NORTHWESTERN ELBERT...HABERSHAM...RABUN...HART...ANDERSON...WESTERN
PICKENS AND OCONEE COUNTIES UNTIL 400 AM EDT...

At 154 AM EDT, Doppler radar indicated the leading edge of an area of
heavy rain along a line extending from 7 miles east of Hiawassee to 3
miles southwest of Homer, and moving east at 15 mph.

Locations to be impacted include...
Anderson, Clemson, Toccoa, Seneca, Hartwell, Walhalla, Clayton,
Clarkesville, Carnesville and Pickens.

Heavy rainfall rates up to 2 inches per hour will be possible in
these areas over the next few hours.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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.

&&

LAT...LON 3420 8309 3427 8312 3423 8335 3446 8340
      3449 8354 3443 8362 3450 8367 3454 8362
      3465 8366 3473 8362 3480 8368 3488 8366
      3499 8353 3500 8352 3499 8352 3500 8311
      3508 8279 3436 8252 3423 8272 3427 8278
TIME...MOT...LOC 0554Z 264DEG 48KT 3496 8362 3431 8354

JPT