Flash Flood in North Carolina, August 15, 2020

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
204 AM EDT Sat Aug 15 2020

.SYNOPSIS...
Numerous to widespread showers and thunderstorms are expected
through Saturday with highs slightly below normal. Thunderstorm
chances diminish Sunday then slowly increase through the week. Highs
will be around normal through the first part of the week then fall
below normal.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1020 pm EDT Friday: With shower coverage remaining robust late
this evening across the NC foothills, and the showers being rather
efficient rain producers with more expected overnight, have opted to
extend the Flash Flood Watch for the same areas as the existing FFA
right through Saturday evening.

Otherwise, water vapor imagery shows the base of a digging trough
steadily advancing eastward into central Tennessee late this
evening. Several spokes of convection ahead of this wave are evident
on regional radars across eastern AL, central GA, and central TN,
however this more robust coverage should encounter weakening
instability as it reaches the southern Appalachians and points east
overnight. Will keep relatively high PoPs going through the
overnight hours, especially west and north, but the diminishing
instability should generally keep the precip rates from getting out
of hand, so no expansion in area of the Watch appears necessary
yet.

PoPs will ramp up a bit sooner than typical diurnal trends indicate
on Saturday, as upper DPVA and jet energy begins to push east into
the area. The best 2+ inch precipitable water values of the event
will occur on Saturday, and the deep forcing, abundant moisture and
slightly improved lapse rates should yield more coverage, stronger
storms, and a slight uptick in the hydro threat with any training
cells. Expansions to the Flash Flood Watch could be needed at some
point Saturday where antecedent rainfall conditions are the wettest,
especially across western NC. Expect mild and muggy conditions
overnight, and then below climo maxes Saturday afternoon given all
the cloud cover.

&&

.SHORT TERM /TONIGHT THROUGH MONDAY/...
As of 200 PM EDT Friday: The mid level trof will be pulling east of
the area by Saturday night. We should have some showers and storms
in the evening, but they will move east of the area leaving a dry
overnight period.  As the trof moves east, a drier air mass will
move into the area for Sunday and Monday as northwest mid level flow
develops. There will be a small chance of a shower or storm each day
but conditions should be quiet overall.

Highs both days will be near climo. Slightly lower dewpoints will
make conditions relatively comfortable for mid August.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 200 PM EDT Friday: Another mid level trof is expected to
develop to our west for the middle to latter part of next week. This
should act to pull deeper moisture back into the area leading to a
more active, mainly diurnal, convective pattern. The increased cloud
cover and rainfall should keep high temperatures in check and a few
degrees below climo through the period.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and Elsewhere: A cluster of tstms continues to impact KHKY
to start the 06z TAF, but should rain out and shift north over the
next couple of hours. However, overall set up is for expanding SHRA
across the area thru the morning hours as an upper disturbance
approaches from the west. A weak wedge-like boundary has set up,
with IFR cigs north of it across the KHKY area. Not confident it
will reach KCLT, but still expect to see some MVFR cigs developing
there and across the Upstate sites thru daybreak. Rain moving into
the French Broad Valley will support MVFR cigs and possibly vsby. A
lull in precip across the Piedmont during the mid-morning thru
midday, but showers continue across the mountains. Then another
round of widespread convection expected late aftn thru the evening.
the aforementioned boundary may set up near KCLT and could result in
a few hours of SHRA/TSRA around. So will go with prevailing TSRA
from 19-02z at KCLT. Expect very slow drying to begin from the west
right around the end of the TAF period, but with low-level moisture
persisting. Light and variable winds will be mainly S to SW with any
mixing tonight through Saturday, except NW at times in the French
Broad Valley tonight. Winds will be briefly gusty near any
thunderstorms.

Outlook: Slightly less thunderstorm coverage is expected Sunday and
Monday compared to recent days, but perhaps still slightly above
normal as low-level moisture continues. An uptick in thunderstorm
coverage is then likely Tuesday through Wednesday. Fog and low
stratus restrictions will be possible each morning, especially over
the usual mountain valleys.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High  83%     Med   75%     High  99%     High  91%
KGSP       High  83%     High  82%     High  97%     High  97%
KAVL       High  81%     High  85%     High  87%     High  86%
KHKY       Med   76%     Med   76%     High  89%     Med   77%
KGMU       High  84%     High  83%     High  96%     High  97%
KAND       High  85%     Med   75%     High  96%     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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Flash Flood Watch through this evening for NCZ033-035>037-056-
     057-501>506.
SC...None.

&&

SYNOPSIS...DEO
NEAR TERM...HG
SHORT TERM...SCW
LONG TERM...SCW
AVIATION...ARK

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1010 PM EDT Fri Aug 14 2020

GAZ010-017-018-026-028-029-NCZ048>053-058-059-062>065-068>072-082-
507>510-SCZ001>014-019-160215-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Madison-Yancey-
Mitchell-Swain-Haywood-Buncombe-Graham-Northern Jackson-Macon-
Southern Jackson-Transylvania-Henderson-Cleveland-Lincoln-Gaston-
Mecklenburg-Cabarrus-Union NC-Rutherford Mountains-
Greater Rutherford-Polk Mountains-Eastern Polk-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Greater Greenville-Spartanburg-Cherokee-York-
Anderson-Abbeville-Laurens-Union SC-Chester-Greenwood-
1010 PM EDT Fri Aug 14 2020

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

.DAY ONE...Tonight.

Numerous showers and thunderstorms will continue to develop across
the region through the overnight hours. The primary threats with
these storms will be cloud-to- ground lightning and locally heavy
rainfall. The storms and heavy rain showers will occasionally become
stationary, posing a threat of excessive rainfall and flash
flooding, especially in locations that have received heavy rainfall
over the past few days.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ033-035>037-056-057-501>506-160215-
Avery-Alexander-Iredell-Davie-Catawba-Rowan-Caldwell Mountains-
Greater Caldwell-Burke Mountains-Greater Burke-McDowell Mountains-
Eastern McDowell-
1010 PM EDT Fri Aug 14 2020

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

This Hazardous Weather Outlook is for the northwest Piedmont,
northern foothills, and Avery county in western North 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...Saturday through Thursday.

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...

Spotter activation may be needed. Please relay any information about
observed severe weather to the NWS while following all local, state,
and CDC guidelines.

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1047 PM EDT Fri Aug 14 2020

NCZ035-036-056-150400-
Iredell NC-Alexander NC-Catawba NC-
1047 PM EDT Fri Aug 14 2020

...A THUNDERSTORM WITH TORRENTIAL RAINFALL WILL IMPACT NORTHEASTERN
CATAWBA...SOUTHERN ALEXANDER AND NORTHWESTERN IREDELL COUNTIES UNTIL
MIDNIGHT EDT...

At 1046 PM EDT, Doppler radar was tracking a thunderstorm with
torrential rainfall 6 miles northeast of Hickory, or near St.
Stephens, moving east at 5 mph.

Locations to be impacted include...
Newton, Hickory, St. Stephens, Conover, Bethlehem, Stony Point,
Claremont, Catawba, Lookout Shoals Lake and Lake Hickory.

Very heavy rainfall rates up to 2 inches per hour will be possible in
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 3568 8130 3585 8130 3594 8100 3570 8099
TIME...MOT...LOC 0246Z 256DEG 6KT 3579 8122

08

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
123 AM EDT SAT AUG 15 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0116 AM     FLASH FLOOD      3 S GLEN ALPINE         35.68N 81.78W
08/15/2020                   BURKE              NC   BROADCAST MEDIA

            FLOODING ON WOOD GLEN DR AT TRESTLEWOOD LN

&&

RWH