Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
646 AM EDT Tue Jul 20 2021

.SYNOPSIS...
An upper-level trough of low pressure will remain just west of the
southern Appalachians today, 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 rain 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 by late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 630 am EDT: The update this morning sharpens up the PoP
gradient between very wet southern sections and a considerably drier
northern tier along and near I-40. Incoming RAP model runs are now
suggesting much heavier QPF in the southern portion of the Watch
area, and some rainfall/runoff issues could be posed southward into
Elbert and Abbeville Counties into the afternoon hours. For now,
these issues appear highly localized and no changes will be made to
the Watch, with the more persistent bands and training still
expected to be mainly from Hart County to Anderson County and points
north.

Otherwise, an upstream 500 mb trough extends from the central
Appalachians to the mid-Mississippi River valley this morning, with
water vapor satellite imagery showing a plume of deep moisture from
the Deep South to the southern Appalachians in advance of the trough
axis. A series of mid-level vorticity lobes will continue to cross
the region from the west today, interacting with the very deep
moisture south of a stationary front parked over the region to
produce moderate to heavy rain showers at times. PoPs and rainfall
rates will remain highest across the Upper Savannah River region and
the extreme southern Appalachians, where southeasterly upslope flow
will enhance the persistent coverage and precipitable water values
remain close to two inches. In addition, the convection-allowing
models have the best rates in this same area going forward, although
the latest RAP runs focus the bulleye nearer Hart/Anderson Counties,
with some runoff issues possible to the south. As mentioned above,
no changes will be made to the FFA at this point. Any diurnal
instability will be confined to the far southern Piedmont, where
sbCAPE values could rise to 1000+ J/kg and generate a few
thunderstorms. The clouds and rainfall will likely cap maximum
temperatures today some 10 to 15 degrees below climo, especially in
the western Upstate and NE GA.

The 500 mb low center west of the Appalachians will gradually fill
or get slowly absorbed tonight, however, upper-level divergence
south of a jet streak axis bisecting the area will continue atop the
region well into the nighttime hours. Modest mid-level drying will
continue along and north of I-40 tonight. The low-level upslope flow
in the southern tier should diminish late this evening as winds in
the 950 to 850 mb layer start to turn more westerly or northerly
with time. PoPs will slowly diminish from north to south as the weak
boundary may also be on the move southward.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 325 AM EDT Tuesday: The short-term fcst picks up at 12z on
Wednesday with a positively tilted upper trof amplifying over New
England while broad upper ridging persists over the rest of the
CONUS. On Wednesday, the deep-lyr moisture will gradually decrease
as winds turn more NWLY and WLY. This will lead to some decrease
in cloud cover and more insolation with high temps on Wednesday
rebounding back into the mid to upper 80s outside of the mtns and
70s to low 80s across the mtns. Lingering moisture will remain
in place as the stationary front remains stalled over the SC
Upstate and central NC. This will allow the diurnal trend of
showers and thunderstorms to return. I kept PoPs capped at chance
for the aftn/evening hours with slightly lower values over our
northern zones. The trof axis is expected to clear the area by
early Thurs with PWATs gradually declining from north to south.
With regards to severe wx potential, conditions are still not
looking very favorable for Wed or Thurs, and we remain under a
general thunderstorm risk per SPC. By Thurs, temps will climb
back to near-normal, if not slightly above.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 305 AM EDT Tuesday: The extended forecast picks up at 12z
on Friday with broad upper trofing still centered over the far NE
CONUS while very broad upper ridging remains in place over the
western 2/3 of the CONUS. Over the next few days, the upper trof
will deamplify, yet some degree of an upper trof will remain over
the Northeast while broad ridging persists over the rest of the
CONUS. Some degree of drying is expected due to NWLY flow across
the fcst area on Friday allowing PWAT values to decrease across
the region. PWATs are expected to gradually increase again over
the weekend and into early next week as a long wave trof digs
across the eastern CONUS. A cold front associated with this trof
may track out of the Ohio Valley early next week and approach
the forecast area. This will lead to an uptick in moisture and
increasing PoPs this weekend and early next week. Temps will be
near-normal for Fri and Sat, and remain at or just above normal
for the rest of the period.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
At KCLT and KHKY: The deeper moisture and forcing will remain
shunted south of a KHKY to KCLT line, but persistent low-level
moisture may lead to TEMPO IFR to MVFR cigs at time at KCLT for a
couple of hour. Shower chances will be fairly spotty given weak
drying behind a departing mid-level wave, and clouds will limit
instability through the day. Anticipate light winds turning around
the dial, but with more of an ENE flow early and WSW flow late.

Elsewhere: Deeper moisture and better forcing south of a stationary
front will keep the potential for showers and low restrictions in
place through the day at the Upstate sites and at KAVL. Anticipate
heavy rainfall rates at times at KAND where better banding of the
precipitation is evident. Expect IFR cigs at times through the
morning, with MVFR bases holding on through the afternoon hours.
Winds will be light but mostly out of the east to northeast, except
becoming light NW at KAVL at times. Lower cigs may return overnight
given the abundant moisture in place.

Outlook: Gradual drying will occur from the north mid to late week,
but with early morning fog or low stratus possible each day. Diurnal
thunderstorm chances will steadily return late week into the weekend.

Confidence Table...

            10-16Z        16-22Z        22-04Z        04-06Z
KCLT       High  92%     High 100%     High 100%     High 100%
KGSP       Low   57%     Low   50%     Med   77%     High 100%
KAVL       Med   60%     High  80%     High  80%     High  87%
KHKY       High  87%     High 100%     High 100%     High 100%
KGMU       Low   55%     Med   65%     Med   67%     High  87%
KAND       High  82%     Med   60%     High  80%     Med   73%

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 this evening for GAZ010-017-018-026-
     028.
NC...None.
SC...Flash Flood Watch through this evening for SCZ001-002-004-005-
     010.

&&

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

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
408 AM EDT Tue Jul 20 2021

NCZ033-035>037-048>053-056>059-065-068>072-082-501>510-SCZ008-009-
014-210815-
Avery-Alexander-Iredell-Davie-Madison-Yancey-Mitchell-Swain-Haywood-
Buncombe-Catawba-Rowan-Graham-Northern Jackson-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-Cherokee-York-Chester-
408 AM EDT Tue Jul 20 2021

This Hazardous Weather Outlook is for Piedmont North Carolina,
western North Carolina, and the eastern Upstate of South Carolina.

.DAY ONE...Today and tonight.

No hazardous weather is expected at this time.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ029-NCZ062>064-SCZ003-006-007-011>013-019-210815-
Elbert-Macon-Southern Jackson-Transylvania-Greenville Mountains-
Greater Greenville-Spartanburg-Abbeville-Laurens-Union SC-Greenwood-
408 AM EDT Tue Jul 20 2021

This Hazardous Weather Outlook is for Elbert County in northeast
Georgia, the extreme southern mountains of western North Carolina,
and parts of Upstate South Carolina.

.DAY ONE...Today and tonight.

Occasionally heavy rain showers, with a few embedded thunderstorms,
will continue across the region today. The main threat will be heavy
rainfall, possibly leading to localized minor flooding. A few cloud-
to-ground lightning strikes will be possible as well.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ010-017-018-026-028-SCZ001-002-004-005-010-210815-
Rabun-Habersham-Stephens-Franklin-Hart-Oconee Mountains-
Pickens Mountains-Greater Oconee-Greater Pickens-Anderson-
408 AM EDT Tue Jul 20 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING...

This Hazardous Weather Outlook is for northeast Georgia and the
western Upstate of 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.

A few thunderstorms today may produce cloud-to-ground lightning
strikes.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to relay any reports of flooding to the
National Weather Service.

HG

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

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

GAZ010-017-018-026-028-029-NCZ062>064-SCZ001>006-010-011-201000-
Elbert GA-Hart GA-Franklin GA-Stephens GA-Rabun GA-Habersham GA-
Transylvania NC-Southern Jackson NC-Macon NC-Greater Pickens SC-
Greater Oconee SC-Abbeville SC-Pickens Mountains SC-Anderson SC-
Oconee Mountains SC-Greenville Mountains SC-Greater Greenville SC-
403 AM EDT Tue Jul 20 2021

...AN AREA OF HEAVY RAIN WILL IMPACT FRANKLIN...STEPHENS...
NORTHWESTERN ELBERT...HABERSHAM...RABUN...HART...SOUTHEASTERN
MACON...CENTRAL GREENVILLE...ANDERSON...NORTHWESTERN ABBEVILLE...
PICKENS AND OCONEE COUNTIES UNTIL 600 AM EDT...

At 402 AM EDT, Doppler radar indicated the leading edge of an area of
heavy rain along a line extending from 11 miles southwest of Franklin
to 4 miles southwest of Commerce, and moving northeast at 15 mph.

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

Heavy rainfall rates up to 2 inches per hour will be possible over
these areas.

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 3427 8312 3423 8335 3446 8340 3449 8354
      3444 8363 3450 8367 3454 8362 3465 8366
      3473 8362 3488 8366 3499 8355 3500 8348
      3501 8351 3501 8352 3507 8259 3446 8232
      3422 8272 3426 8279 3420 8309
TIME...MOT...LOC 0802Z 043DEG 5KT 3507 8353 3417 8352

JPT

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

GAZ029-201245-
Elbert GA-
753 AM EDT Tue Jul 20 2021

...ADDITIONAL HEAVY SHOWERS WILL IMPACT ELBERT COUNTY THIS MORNING...

At 748 AM EDT, Doppler radar was tracking an area of very heavy
precipitation encroaching from the west.  On top of storm total
rainfall amounts of 2 to 3 inches, additional heavy rain this
morning will aggrevate areas of standing water and possibly result
in small streams coming out of their banks.

Please remain wary of high water conditions and rising stream levels
this morning.

LAT...LON 3398 8261 3397 8264 3399 8265 3397 8278
      3399 8283 3398 8286 3401 8291 3401 8294
      3403 8294 3405 8299 3415 8307 3422 8295
      3429 8277 3427 8274 3415 8272 3413 8268
      3409 8264 3407 8265 3403 8260 3396 8257
TIME...MOT...LOC 1148Z 269DEG 17KT 3396 8294

CSH