Tornadoes and Flash Flooding in North Carolina, August 17 to 18, 2021

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1011 AM EDT Tue Aug 17 2021

.SYNOPSIS...
The remnants of tropical cyclone Fred will generate heavy rainfall
across the forecast area today and into tonight. Expect cooler than
normal temperatures today with a warming trend through the end of
the week. Abundant moisture will continue across the region through
much of the week leading to periods of heavy rainfall and isolated
strong thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 10am EDT Tuesday: Forecast continues on track with widespread
rain and some thunder.  Main area of precipitation associated with
passage of T.D./remnants of Fred now coming into the western half of
the CWA.  This rain will spread eastward over time as Fred passes
through today and tonight.  Main risk is flooding, per the Flash
Flood watch, with some chance for a brief tornado in stronger cells.

There remains some annoying spread in the QPF from the model
guidance, with the GFS still sticking to its low amounts, so we
continue to discount that solution. The QPF guidance from HPC was
generally accepted, which concentrates the highest amounts in the
S/SE upslope areas of southern NC and near the Escarpment. Without
any sort of sfc boundary around, the main focus will be closer to
the Escarpment, and thus our QPF has gone up a bit in the upslope
areas, but down across the wrn Piedmont. Of note is the somewhat
rare High Risk in the Excessive Rain Outlook in the headwaters of
the French Broad River. This makes sense because of the very high
rainfall in that location early Monday. Based on the new QPF, we are
comfortable with keeping the extent of the Flash Flood Watch right
where it is, with no expansion eastward at this time. That doesn't
mean that areas to the east are completely out of the woods on this
one. There remains a small possibility of a band training over the
Charlotte metro area, for example, so we should not let our guard
down. The general 4-6" of rainfall in the next 24 hours along/near
the Blue Ridge Escarpment raises the threat of landslides and slope
failures, so we will continue to highlight that in our Flash Flood
Watch. The end time of the Watch still looks good as model guidance
has sped up the transit and departure of the system.

The other main threat will be for tornadoes this afternoon and
evening along and east of the Escarpment. The new Day 1 Slight Risk
looks good. Timing looks favorable/ideal across a large part of the
fcst area with the main system lifting northward late in the day. A
favorable overlap of low level shear of 35-50kt in the right half
of the system with a tongue of 1500-2000 J/kg of sfc-based CAPE
lifting into northeast GA and the Upstate from 18Z onward suggest
a good potential for rotating updrafts. The 00Z HREF shows that to
such an extent that a Tornado Watch is anticipated at some point
later today for a large chunk of the area, so be on the lookout
for that. The threat should diminish by mid-evening as the shear
lifts northward and we lose the buoyancy in the environment.

We will monitor the development of sfc winds later today, and
could issue a Wind Advisory for parts of the area based on the
idea that trees would be blown down from 30-35 mph gusts because
of saturated soils.

The trend toward a faster system has resulted in a quicker lowering
of precip probs late tonight and early Wednesday.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 210 AM EDT Tuesday...The remnants of TC Fred continue to push
up the spine of the Apps Wed. A trailing wake trof will persist
however, and provide a focusing zone for afternoon precip. Deep
convec chances look low as soundings show dense drying air aloft and
warming temps arnd h7. Have capped general thunder chances at 30-35%
for the afternoon with the best chances occurring across the nrn
zones. Winds will begin to weaken across the the mtn tops with only
low-end gusts likely by the end of the day. The atmos moistens up a
little Thu as a cold front and energized upper trof approach the
mtns. With lowering h5 heights, mlvl LRs will increase leading to a
better chance of afternoon thunder. Expect general thunder across
the non/mtns, but a few stronger or loosely organized cells are
possible across the higher terrain as bulk shear increases to arnd
30 kts. Max temps will return to normal levels in persistent sw/ly
to w/ly aided by llvl downslope flow. Mins will remain elevated a
couple degrees abv normal thru the period.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 250 AM EDT Tuesday...A broad ulvl trof will persist across the
region thru Sat as a reinforcing shot of vort energy traverse a wrn
ridge and crosses the area by Sat night. The surface pattern will
feature hipres to the south and llvl winds will align w/ly Fri,
which will inhibit the convec potential somewhat, but overall weak
forcing and destabilization will likely overcome the sbCIN and allow
for sct pulse-type tstms Fri afternoon. On Sat, the upper energy and
good moisture transport from the wrn GOM will combine and increase
PWATS back to near 2.0 inches. With the upper trof hanging out and
nw/ly mech lift, there could be a few deep cells producing high
precip rates and possible flooding issues across the higher terrain.
A strong ulvl high develops across the Southern Plains Sun and the
FA will come under the influence of increased subs and weak shear.
Still, anticipate climo PoPs and afternoon tstms to develop typical
of late Aug both Sun and Mon afternoons. Max and temps will remain
right around normal levels thru the period.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Aviation weather looks grim over the next
18 hours or so as Fred or its remnants approach this morning and
track over the srn Appalachians later today. We are locked in to a
S/SE upslope flow of deep tropical moisture, which will keep the
ceiling down in the IFR/LIFR categories at all sites through the
morning hours, while more intermittent shower activity spreads up
from the south/southeast ahead of the storm. A shower or storm could
develop at any time at any location in this regime. That makes TAFs
necessarily pessimistic, with prevailing MVFR vis and IFR ceiling
for most of the day, except at KCLT where coverage might be a bit
less allowing some improvement to MVFR with a few holes from time
to time. As the main system moves past late in the day, wind should
become gusty from the SE. This will probably lead to a low level
wind shear at least at KAVL. Once the center passes this evening,
very slow improvement should begin with drier air wrapping in from
the SW. Guidance keeps prevailing IFR restrictions at this time,
and this was generally accepted. It might take until sunrise
and the development of some downslope flow behind the remnant
circulation to scour out the IFR. Either way, quick improvement
will take place after sunrise Wednesday.

Outlook: A gradual downward trend in diurnal convection is expected
Wednesday in the wake of Fred's remnants, then continuing during
the latter half of the week. Widespread low stratus and areas of
fog are expected each morning through at least late-week.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       Med   77%     High  84%     Low   58%     High  81%
KGSP       Med   75%     Med   72%     Med   78%     Med   75%
KAVL       High  86%     High  90%     High  87%     High 100%
KHKY       Med   64%     Low   56%     High  81%     High  96%
KGMU       High  86%     Med   63%     Med   71%     High  86%
KAND       High  83%     Med   76%     Med   64%     Med   79%

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 Wednesday morning for GAZ010-017-018-
     026-028-029.
NC...Flash Flood Watch through Wednesday morning for NCZ033-048>053-
     058-059-062>065-501>510.
SC...Flash Flood Watch through Wednesday morning for SCZ001>007-
     010>012-019.

&&

SYNOPSIS...SBK
NEAR TERM...PM/WJM
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1055 AM EDT Tue Aug 17 2021

GAZ010-NCZ048>050-052-053-059-062>065-503>510-SCZ001>007-010>012-019-
181500-
Rabun-Madison-Yancey-Mitchell-Haywood-Buncombe-Northern Jackson-
Macon-Southern Jackson-Transylvania-Henderson-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-
Anderson-Abbeville-Laurens-Greenwood-
1055 AM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH WEDNESDAY MORNING...
...TORNADO WATCH 444 IN EFFECT UNTIL 7 PM EDT THIS EVENING...

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

   Tornado Watch.
   Flash Flood Watch.

Widespread showers with embedded thunderstorms are likely today into
tonight as the remnants of Fred track across the southern
Appalachians. Cloud-to-ground lightning strikes, heavy rainfall, and
isolated tornadoes are the main impacts. Heavy rainfall will likely
lead to flash flooding, especially along the Blue Ridge Escarpment
and areas that receive multiple rounds of heavy rainfall. Isolated
tornadoes are possible this afternoon and evening across the North
Carolina Piedmont, South Carolina Upstate, and Northeast Georgia.

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

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

   Flash Flood Watch.

Flash Flood Watch through early Wednesday morning.

.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.

NCZ068-SCZ008-013-181500-
Cleveland-Cherokee-Union SC-
1055 AM EDT Tue Aug 17 2021

...TORNADO WATCH 444 IN EFFECT UNTIL 7 PM EDT THIS EVENING...

This Hazardous Weather Outlook is for piedmont North Carolina and
upstate 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.

   Tornado Watch.

Deep tropical moisture from the remnants of Tropical Depression Fred
will produce periodic heavy rainfall with embedded thunderstorms
today into tonight. The main impacts are cloud-to-ground lightning,
isolated tornadoes, and heavy rainfall leading to the potential for
isolated flash flooding.

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

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.

NCZ035>037-056-057-069>072-082-SCZ009-014-181500-
Alexander-Iredell-Davie-Catawba-Rowan-Lincoln-Gaston-Mecklenburg-
Cabarrus-Union NC-York-Chester-
1055 AM EDT Tue Aug 17 2021

This Hazardous Weather Outlook is for piedmont North Carolina and
upstate South Carolina.

.DAY ONE...Today and tonight.

Deep tropical moisture from the remnants of Tropical Depression Fred
will produce periodic heavy rainfall with embedded thunderstorms
today into tonight. The main impacts are cloud-to-ground lightning,
isolated tornadoes, and heavy rainfall leading to the potential for
isolated flash flooding.

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

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.

NCZ033-051-058-501-502-181500-
Avery-Swain-Graham-Caldwell Mountains-Greater Caldwell-
1055 AM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH WEDNESDAY MORNING...

This Hazardous Weather Outlook is for western North 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.

Widespread showers with embedded thunderstorms are likely today into
tonight as the remnants of Fred track across the southern
Appalachians. Cloud-to-ground lightning strikes, heavy rainfall, and
isolated tornadoes are the main impacts. Heavy rainfall will likely
lead to flash flooding, especially along the Blue Ridge Escarpment
and areas that receive multiple rounds of heavy rainfall. Isolated
tornadoes are possible this afternoon and evening across the North
Carolina Piedmont, South Carolina Upstate, and Northeast Georgia.

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

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

   Flash Flood Watch.

Flash Flood Watch through early Wednesday morning.

.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.

GAZ017-018-026-028-029-181500-
Habersham-Stephens-Franklin-Hart-Elbert-
1055 AM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT THROUGH WEDNESDAY MORNING...
...TORNADO WATCH 443 IN EFFECT UNTIL 1 PM EDT THIS AFTERNOON...

This Hazardous Weather Outlook is for northeast Georgia.

.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.

   Tornado Watch.
   Flash Flood Watch.

Isolated tornadoes are possible this afternoon into this evening.
Excessive rainfall from Fred's remnants could lead to flash flooding
today into tonight.

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

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

   Flash Flood Watch.

Flash Flood Watch in effect until early Wednesday morning.

.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.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1023 AM EDT Tue Aug 17 2021

GAZ029-171500-
Elbert GA-
1023 AM EDT Tue Aug 17 2021

...A strong thunderstorm will impact portions of Elbert County
through 1100 AM EDT...

At 1022 AM EDT, Doppler radar was tracking a strong thunderstorm 11
miles south of Elberton, or 5 miles southwest of Nancy Hart State
Park, moving north at 30 mph.

HAZARD...Winds in excess of 40 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Elberton, Bowman, Nancy Hart State Park, Middleton, Russell State
Park, Lake Russell, Dewy Rose, Rock Branch, Fortsonia and Sweet City.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

A Tornado Watch remains in effect until 100 PM EDT for northeastern
Georgia.

&&

LAT...LON 3399 8283 3398 8286 3400 8288 3401 8294
      3403 8294 3404 8298 3408 8301 3423 8306
      3423 8300 3421 8298 3425 8291 3429 8278
      3427 8275 3398 8272 3397 8278
TIME...MOT...LOC 1422Z 170DEG 24KT 3394 8284

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

CSH