Tornadoes and Damaging Winds in Georgia, April 13, 2020

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
224 AM EDT Mon Apr 13 2020

.SYNOPSIS...
Drier air will make it's way into the region later today in the wake
of a strong cold front.  A wave of low pressure moving along the
stationary front located just south of our region will bring a
chance of precipitation back to the area late Tuesday and early
Wednesday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 145 AM EDT: Main update for the 06Z TAF issuance along
with minor adjustments made to temperatures, PoPs/weather, and
winds to coincide with latest trends, as the rest of the near
term forecast remains on track. The first line of convection
continues to slowly push eastward into the FA attm, with the
secondary line continuing to push across central TN/AL attm. A
Flash Flood Watch, Wind Advisories, and a Tornado Watch remain
in effect for the area. The new Tornado Watch (#116) includes
most of the FA, including the Charlotte-Metro area.

Previous discussion: Strong low level warm advection has squeezed
residual in-situ cold air damming to a small area along the eastern
Blue Ridge escarpment, and even this will likely erode in due time.
Per the latest SPC Mesoanalysis...weak surface-based instability as
developed into the upper Savannah River Valley, while sbCAPE > 1000
J/kg has...alarmingly...developed north of the ATL metro area.
Strong southerly flow and steepening lapse rates responding to
strengthening deep-layer forcing will continue to draw this
instability northeastward into the forecast area over the next 3 to
6 hours...ahead of the QLCS. Shear parameters will be through the
roof during this time as 60-70 kt LLJ translates across the
area...supporting outrageous (> 500) values of 0-1 km SRH.
Considering the expected degree of instability, this is looking more
like a "QLCS with embedded supercell structures" type of event,
rather than the "low-topped QLCS with mesovortex" events that we're
used to. That being the case, the SRH parameters are downright
scary, and portend the potential for a strong/damaging tornado or
two. Swaths of downburst damage also appear likely...if based on
nothing else than good old-fashioned convective mixing.

Speaking of which, gradient winds will also be an issue overnight
and into the daytime period Mon. With the lowering jet core, shallow
mixing will allow stg wind gusts to reach the sfc. With moist soils
these winds could down isol weak or dead trees. A Wind Advisory is
in effect for much of the forecast area.

Rainfall continues to pile up across southwest NC...which has
generally seen totals of 1-2 inches since Sunday morning. Widespread
moderate to heavy rain showers will persist across these areas for
the next couple of hours, followed by likely intense rainfall rates
within the QLCS. Storm totals of 2 to 4 inches, with locally higher
amounts therefore appear to be very doable, and this will likely be
enough to support localized hydro issues in the Little Tennessee
basin and in the upper French Broad River basin.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY NIGHT/...
As of 1215 PM EDT Sunday: A closed 500 mb low pressure center will
be positioned over the Great Lakes Monday night, with an associated
broad trough covering most of the CONUS. As the closed system lifts
over eastern Canada, trailing and reinforcing shortwaves will dive
through the northern Plains to keep a broad trough axis in place
through the day on Tuesday. With low-level flow maintaining a
southerly component, clouds could return in weak moist upglide
through the day. The best upstream vorticity lobe will likely cross
the southern Appalachians Tuesday night into Wednesday. This appears
to be associated with a narrow band of moisture and frontogenetical
forcing which maximizes over the southern Appalachians circa 06Z to
12Z Wednesday. This could overlap just enough with cold air to
support some high elevation snow showers, with rain showers in most
other areas, and possibly isolated thunderstorms on the warm side of
the developing front over the lower Piedmont.

The frontal boundary will then gradually slide southeast through
Wednesday, with drying and cooling developing from the northwest.
Temperatures will dip well below climo, and frost and freeze
concerns will have to be considered for the mountains and the I-40
corridor for Wednesday night.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 1230 PM EDT Sunday: Relatively zonal upper flow will set up
over the southeast on Thursday, with most upstream energy moving
east of the Rockies Thursday night, and across the Midwest on
Friday. Return flow moisture ahead of this system and the associated
cold front will bring cloudiness back on Friday, and possibly low
end PoPs for showers by late day. The passing trough will move off
the East coast early in the weekend. The better support should pass
mainly north of the area, but a brief shot of deeper moisture and
forcing should cross the southern Appalachians and surrounding areas
with a weak cold front mainly Friday night. Otherwise, westerly flow
and drying conditions will return through Saturday. Mid to high
level moisture may sneak back into the picture from the west Sunday,
with a return of late day shower PoPs. Temperatures will see a
gradual warming trend to above climo values by the end of the period.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
At KCLT and Elsewhere: A mixture of MVFR/IFR prevails at all TAF
sites this morning, as showers and thunderstorms continue to push
into the area from the west. Through the morning hours, expect this
activity to bring periods of +RA and strong to severe +TSRA, along
with reduced vsbys and LIFR cigs, ahead of the approaching cold
front. South-southeast winds AOB 20 kts with higher gusts (30 to 35
kts) are expected through this morning ahead of the front. However,
will note periods of westerly winds will be possible with
convection, as noted by TEMPO groups. Behind the front, expect
conditions to improve from west to east, with convection tapering
off and cigs improving as clouds scatter out. With conditions
improving to VFR, expect winds to veer to the SW, with gusts
subsiding this afternoon.

Outlook: Potential for rain and flight restrictions Tuesday night
into Wednesday. Otherwise expect VFR.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High  80%     High  88%     High 100%     High 100%
KGSP       High  85%     High  94%     High 100%     High 100%
KAVL       High  80%     High  95%     High  96%     High  94%
KHKY       High  89%     High  82%     High 100%     High 100%
KGMU       High  81%     High  92%     High  99%     High 100%
KAND       High  87%     High  97%     High 100%     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...Flash Flood Watch until 8 AM EDT this morning for GAZ010-017.
     Wind Advisory until 4 PM EDT this afternoon for GAZ018-026-028-
     029.
NC...Flash Flood Watch until 8 AM EDT this morning for NCZ033-
     048>053-058-059-062>065-501-503-505-507-509.
     Wind Advisory until 4 PM EDT this afternoon for NCZ033-035>037-
     048>053-056>059-062>065-068>072-082-501>510.
SC...Flash Flood Watch until 8 AM EDT this morning for SCZ001>003.
     Wind Advisory until 4 PM EDT this afternoon for SCZ003>014-019.

&&

SYNOPSIS...DEO
NEAR TERM...SBK/12
SHORT TERM...HG
LONG TERM...HG
AVIATION...12

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
157 AM EDT Mon Apr 13 2020

GAZ018-026-028-029-NCZ035>037-056-057-068>072-082-502-504-506-508-
510-SCZ004>014-019-140600-
Stephens-Franklin-Hart-Elbert-Alexander-Iredell-Davie-Catawba-Rowan-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
Greater Caldwell-Greater Burke-Eastern McDowell-Greater Rutherford-
Eastern Polk-Greater Oconee-Greater Pickens-Greater Greenville-
Spartanburg-Cherokee-York-Anderson-Abbeville-Laurens-Union SC-
Chester-Greenwood-
157 AM EDT Mon Apr 13 2020

...WIND ADVISORY IN EFFECT UNTIL 4 PM EDT THIS AFTERNOON...
...TORNADO WATCH 116 IN EFFECT UNTIL 8 AM EDT THIS MORNING...

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

   Tornado Watch.
   Wind Advisory.

Flash flooding may also develop in areas that see multiple rounds of
heavy rainfall.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

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

   Tornado Watch.
   Wind Advisory.

.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.

GAZ010-017-SCZ001-002-140600-
Rabun-Habersham-Oconee Mountains-Pickens Mountains-
157 AM EDT Mon Apr 13 2020

...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT THIS MORNING...
...TORNADO WATCH 116 IN EFFECT UNTIL 8 AM EDT THIS MORNING...

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.

   Tornado Watch.
   Flash Flood Watch.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

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.

.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.

NCZ051-052-058-140600-
Swain-Haywood-Graham-
157 AM EDT Mon Apr 13 2020

...WIND ADVISORY IN EFFECT UNTIL 4 PM EDT THIS AFTERNOON...
...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT THIS MORNING...
...TORNADO WATCH 113 IN EFFECT UNTIL 2 AM EDT EARLY THIS MORNING...

This Hazardous Weather Outlook is for 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.

   Tornado Watch.
   Flash Flood Watch.
   Wind Advisory.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

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

   Flash Flood Watch.
   Wind Advisory.

.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.

NCZ033-048>050-053-140600-
Avery-Madison-Yancey-Mitchell-Buncombe-
157 AM EDT Mon Apr 13 2020

...WIND ADVISORY IN EFFECT UNTIL 4 PM EDT THIS AFTERNOON...
...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT THIS MORNING...

This Hazardous Weather Outlook is for 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.
   Wind Advisory.

A line of showers and embedded strong to severe thunderstorms will
move into the area from the west. This activity will pose a threat of
damaging winds and perhaps an isolated tornado as it moves across
the area through daybreak.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

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

   Flash Flood Watch.
   Wind Advisory.

.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.

NCZ059-062>065-501-503-505-507-509-SCZ003-140600-
Northern Jackson-Macon-Southern Jackson-Transylvania-Henderson-
Caldwell Mountains-Burke Mountains-McDowell Mountains-
Rutherford Mountains-Polk Mountains-Greenville Mountains-
157 AM EDT Mon Apr 13 2020

...WIND ADVISORY IN EFFECT UNTIL 4 PM EDT THIS AFTERNOON...
...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT THIS MORNING...
...TORNADO WATCH 116 IN EFFECT UNTIL 8 AM EDT THIS MORNING...

This Hazardous Weather Outlook is for western North Carolina 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.

   Tornado Watch.
   Flash Flood Watch.
   Wind Advisory.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

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.
   Wind Advisory.

.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.

12

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
959 PM EDT Sun Apr 12 2020

NCZ051-058-130245-
Graham NC-Swain NC-
959 PM EDT Sun Apr 12 2020

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL SWAIN AND GRAHAM
COUNTIES UNTIL 1045 PM EDT...

At 958 PM EDT, Doppler radar was tracking a strong thunderstorm 11
miles northwest of Murphy, moving northeast at 60 mph.

Locations to be impacted include...
Bryson City, Robbinsville, Cherokee, Town Of Santeetlah, Smoky
Mountains-Deep Creek, Smoky Mountains-Fontana Area, Lake Santeetlah,
Fontana Lake, Fontana Village and Smoky Mountains-Twentymile Creek.

Wind gusts up to 50 mph and pea size hail 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.

&&

A Tornado Watch remains in effect until 200 AM EDT for western North
Carolina.

LAT...LON 3537 8401 3541 8402 3547 8392 3552 8388
      3553 8382 3556 8377 3558 8360 3556 8358
      3556 8350 3560 8345 3549 8329 3547 8332
      3547 8334 3543 8336 3525 8381 3525 8385
      3522 8396 3524 8401 3531 8404 3535 8404
TIME...MOT...LOC 0158Z 241DEG 55KT 3522 8415

RM