Flash Flood Warning 12, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
622 AM EDT Tue Aug 5 2025

.SYNOPSIS...
A wedge of cool and moist air lingers through much of the
week before a potential coastal low erodes the wedge this
weekend. Although a warming trend is expected to begin Wednesday,
below normal high temperatures are expected to continue through
at least Saturday. Rain chances remain, with the potential for
locally heavy rainfall each day.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 620 AM EDT Tuesday...

Key Messages:

1) Well Below Normal High Temps Expected Again Today Thanks to Cold
Air Damming

2) Widespread Rain Expected through at Least this Afternoon

3) Locally Heavy Rainfall May Lead to Isolated Areas of Flash
Flooding

Light to moderate rain continues lifting northeast across the
forecast areas this morning, mainly along and south of I-85.
Coverage will continue to blossom throughout the morning hours. Have
already seen some 1 inch per hour rain rates at times this morning
so additional Flood Advisories and/or Flash Flood Warnings are
possible throughout the morning or early afternoon hours.

Otherwise, the southwestern periphery of a sfc high will continue to
nose down into the southern Appalachians throughout the near term
keeping cold air damming around. With multiple shortwaves expected
to lift northeast across the western Carolinas and northeast Georgia
through tonight, rain will stick around through at least this
afternoon. A brief lull should develop this evening before another
round of rain develops tonight into early Wednesday morning. With
CAD expected to limit instability again today, embedded thunder
should be hard to come by. However, a few of the CAMs depict some
MUCAPE developing across the SW NC mountains and the far SE fringe
of the forecast area during peak heating this afternoon so
maintained chance thunder across these areas. Otherwise, thunder is
not expected for the remainder of the forecast area. The main
concern during the near term will be the potential for excessive
rainfall. With wet antecedent conditions in place and with rainfall
totals expected to slowly pile up, locally heavy rainfall may lead
to isolated areas of flash flooding. Opted not to issue a Flood
Watch due to the fact that any flash flooding concerns will remain
isolated and as the lack of instability will help keep extreme rain
rates at bay. Rainfall amounts from 1-2.5 inches can be expected
across much of the forecast area through the near term, with lower
amounts expected across the NC mountains (outside of the favored
E/SE upslope areas). Thus, the day 1 WPC Excessive Rainfall Outlook
that depicts a slight risk for most locations along the escarpment
and east appears well placed. Per usual, locally higher rainfall
totals are possible and will be highly dependent on where the
heaviest downpours develop.

CAD will once again allow for well below normal temps this
afternoon. Highs will struggle to reach into the low to mid 70s east
of the mountains and the lower 60s to mid 70s across the mountains.
These forecast temp values will lead to high around 13-18 degrees
below normal for most locations. Mostly cloudy skies as well as
persistent rain may further limit how warm we get today so highs
could end up a few degrees cooler than forecast. Lows tonight will
fall into the mid 50s to mid 60s, ending up a few degrees below
normal for most locations east of the mountains.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Key Messages:

1) Cold air damming remains and keeps high temperatures below
normal.

2) Rain chances continue through the period, although the potential
for organized areas of precip...with a transition to more of a
diurnally-driven convective regime is expected.

As of 110 am EDT Tuesday: The upper trough across the Deep South
and Tenn Valley will continue to drift east and weaken through
the short term, with a resultant weakening of wind fields/upslope
& isentropic flow. Overall support for organized areas of precip
impacting the forecast area will therefore steadily decrease during
the mid-week period, with a diminishing PoP trend. Meanwhile,
the upper flow over the northeast Conus and southeast Canada
will remain broadly confluent through the period, with surface
high pressure expected to move only slowly across New England and
southern Quebec, supporting inverted ridging and continued...albeit
weakening cold air damming on the east side of the Appalachians
through the period. This will limit diurnal destabilization across
the heart of our CWA through the period, although some degree of
instability is expected along the southern and western periphery of
the area each afternoon. Therefore, the highest chances for showers,
along with increasing chances for thunderstorms (PoPs of 50-60% Wed
and Thu afternoon) will be in these areas...although moisture will
be sufficient to advertise chance PoPs across the interior of the
CWA as well. Temperatures will steadily moderate due to weakening
CAD as well as a lack of widespread/persistent precipitation to
reinforce the cold pool. Nevertheless, cloud cover and E/NE low
level flow will result in high temperatures remaining a solid 10+
degrees below climo in most areas.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Key Messages

1) Weakening cold air damming lingers through at least Saturday.

2) Confidence is low regarding potential coastal low impacts
this weekend.

3) Forecast temperatures slowly increase but remain below normal
until at least Monday.

As of 130 am EDT Tuesday: The upper trough just west of the forecast
area will continue to weaken during the early part of the extended,
evolving into more of a weakness in a re-ascendant subtropical
ridge over the weekend. Inverted surface ridging will remain in
place on the east side of the Appalachians through the weekend,
albeit in a weakening state as parent surface high pressure
drifts southeast off the New England coast. Global model guidance
remains in generally good agreement in spinning up a weak tropical
disturbance somewhere near the Carolina coast during the weekend,
although they differ greatly in terms of position and eventual
track. Low level flow responding to this feature will likely be
the final death knell for cold air damming across our area, and
depending upon the track of the low, could result in deepening
NE flow that dries out the forecast area during the latter half
of the period. OR...the low could move inland (as depicted by
the 12Z ECMWF) and bring about the potential return of widespread
precip to at least a portion of the CWA. In light of the inherent
uncertainty, PoPs and temps are allowed to trend toward climatology
during the latter half of the extended, with generally scattered,
mostly diurnal convection advertised each day, and a steady warming
trend culminating in forecast max temps falling only a degree or
so of climo by Day 7/Monday.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Cold air damming remains in place through
the 12Z TAF period keeping rain and restrictions around with very
little improvement expected. This will also allow winds to remain NE
east of the mountains and E/SE winds across the mountains. Seeing
mostly MVFR to IFR restrictions across the terminals as of 12Z and
should these restrictions continue through the TAF period. Periods
of RA or +RA could lead to slight or brief improvement of cigs and
lower vsbys at times this morning/early afternoon. +RA could cause
cigs to lift to MVFR or VFR levels at times. 06Z CAMs are in better
agreement regarding a brief window of drier conditions develop this
evening so went with PROB30s instead of prevailing RA from ~00Z-06Z
(22Z-04Z at KAVL) Wednesday. CAMs generally agree that rain chances
will increase again overnight into Wednesday morning so went with
prevailing RA for now.

With the KGMU ASOS offline, will not amend the TAF until OBS start
flowing again.

Outlook: Drier conditions return Wednesday evening but rain chances
look to return Wednesday night. Cold air damming sticks around
through the workweek keeping rain chances as well as periodic
restrictions around. Embedded thunderstorms will be possible each
afternoon and evening but confidence is low.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

SYNOPSIS...JDL
NEAR TERM...AR
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...AR

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
310 AM EDT Tue Aug 5 2025

NCZ033-035>037-048>052-057>059-070>072-082-501-502-SCZ009-014-060715-
Avery-Alexander-Iredell-Davie-Madison-Yancey-Mitchell-Swain-Haywood-
Rowan-Graham-Northern Jackson-Gaston-Mecklenburg-Cabarrus-Union-
Caldwell Mountains-Greater Caldwell-York-Chester-
310 AM EDT Tue Aug 5 2025

This Hazardous Weather Outlook is for Piedmont North Carolina,
western North Carolina and Upstate 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.

GAZ010-017-018-026-028-029-NCZ053-056-062>065-068-069-503>510-SCZ008-
010>013-019-101>109-060715-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Buncombe-Catawba-Macon-
Southern Jackson-Transylvania-Henderson-Cleveland-Lincoln-
Burke Mountains-Greater Burke-McDowell Mountains-Eastern McDowell-
Rutherford Mountains-Greater Rutherford-Polk Mountains-Eastern Polk-
Cherokee-Anderson-Abbeville-Laurens-Union-Greenwood-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Central Greenville-Southern Greenville-
Northern Spartanburg-Southern Spartanburg-
310 AM EDT Tue Aug 5 2025

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

.DAY ONE...Today and tonight.

Widespread moderate to occasionally heavy rain will continue across
the western Carolinas and northeast Georgia before tapering off to
scattered showers late this morning into the afternoon. Locally
excessive rainfall and isolated flash flooding are possible along
smaller streams and in urban areas, especially across upstate South
Carolina, northeast Georgia, and the foothills and southern mountains
of North Carolina.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

Lane