Severe Thunderstorm Warning 44, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1049 PM EDT Sun Apr 12 2020

.SYNOPSIS...
A strong storm system with abundant moisture will cross the
Southeast, bringing a threat of severe weather and flooding to our
area lasting into Monday morning. Dry and cooler weather will return
Monday night following a 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 MONDAY MORNING/...
s of 1030 pm...QLCS is organizing from AL into far southern
middle TN at this time, and this will be the main "show' in terms of
the severe weather potential over our area as it moves quickly
E/NE...likely pushing into far western portions of the CWA by around
06Z. 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 MONDAY 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 /03Z MONDAY THROUGH FRIDAY/...
At KCLT and Elsewhere: Much of the terminal forecast area is
experiencing a bit of a lull in SHRA at this time. However, this
will not last, as additional shower activity will impact much of the
area in the 1-3 hour time frame. LIFR cigs will persist at most
terminals through at least the evening, while reduced visby will
occur, mainly in association with showers. However, areas of fog may
reduce visby to less than 2SM, esp at the Upstate SC terminals this
evening as warmer/very moist air continues to displace residual cool
air wedge tucked up next to the high terrain. S/SE winds will
continue to increase through the evening and early morning hours
ahead of a cold front, becoming strong and very gusty, with gusts of
25 to 35 kts expected at most terminals.

A line of strong to severe thunderstorms is expected to move quickly
across the forecast area in the 05-10Z time frame. This will likely
bring about a shift to westerly winds, which could gust to more than
35 kts. Upstream convective trends will continue to be monitored to
assess the need to add a tempo for strong westerly gusts to coincide
with categorical TSRA. Cigs and visby will improve quickly behind
the squall line Monday morning, but winds are expected to remain
quite gusty behind the front as they shift to the SW.

Outlook: VFR conditions expected to continue thru Tuesday. The next
chance for rain and possible restrictions will be Tue night thru
Wednesday.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High  89%     High  93%     High 100%     High 100%
KGSP       High  88%     High  84%     High 100%     High 100%
KAVL       High  86%     Med   76%     High 100%     High 100%
KHKY       High  85%     Med   70%     High 100%     High 100%
KGMU       High  84%     Med   72%     High 100%     High 100%
KAND       Med   71%     Med   70%     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 Monday for GAZ010-017.
     Wind Advisory until 4 PM EDT Monday for GAZ018-026-028-029.
NC...Flash Flood Watch until 8 AM EDT Monday for NCZ033-048>053-058-
     059-062>065-501-503-505-507-509.
     Wind Advisory until 4 PM EDT Monday for NCZ033-035>037-048>053-
     056>059-062>065-068>072-082-501>510.
SC...Flash Flood Watch until 8 AM EDT Monday for SCZ001>003.
     Wind Advisory until 4 PM EDT Monday for SCZ003>014-019.

&&

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

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
908 PM EDT Sun Apr 12 2020

GAZ018-026-028-029-NCZ035>037-056-057-068>072-082-502-504-506-508-
510-SCZ004>014-019-140115-
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-
908 PM EDT Sun Apr 12 2020

...WIND ADVISORY IN EFFECT UNTIL 4 PM EDT MONDAY...

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.

   Wind Advisory.

Periods of moderate to heavy rain will continue into the evening
hours as a warm front moves over the region ahead of a strong low
pressure system. Isolated to widely scattered thunderstorms will
also bring a threat of cloud to ground lightning.

As the warm front shifts north of the region tonight, a line of
showers and embedded strong to severe thunderstorms is expected to
move into the area from north Georgia and east Tennessee. This
activity will pose a threat of damaging winds as well as isolated
tornadoes as it moves across the area between midnight and daybreak.
One or two strong tornadoes cannot be ruled out. 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.

   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.

GAZ017-SCZ001-002-140115-
Habersham-Oconee Mountains-Pickens Mountains-
908 PM EDT Sun Apr 12 2020

...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT MONDAY...

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.

   Flash Flood Watch.

In addition to the threat of heavy rainfall and localized flooding,
isolated to widely scattered thunderstorms will bring a threat of
cloud to ground lightning this evening.

As a warm front shifts north of the region tonight, a line of
showers and embedded strong to severe thunderstorms is expected to
move into the area from the west. This activity will pose a threat
of damaging winds as well as isolated tornadoes as it moves across
the area between midnight and 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.

.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.

NCZ051-052-058-059-062>064-140115-
Swain-Haywood-Graham-Northern Jackson-Macon-Southern Jackson-
Transylvania-
908 PM EDT Sun Apr 12 2020

...WIND ADVISORY IN EFFECT UNTIL 4 PM EDT MONDAY...
...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT MONDAY...
...TORNADO WATCH 113 IN EFFECT UNTIL 2 AM EDT MONDAY...

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>050-053-065-501-503-505-507-509-SCZ003-140115-
Avery-Madison-Yancey-Mitchell-Buncombe-Henderson-Caldwell Mountains-
Burke Mountains-McDowell Mountains-Rutherford Mountains-
Polk Mountains-Greenville Mountains-
908 PM EDT Sun Apr 12 2020

...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT MONDAY...
...WIND ADVISORY IN EFFECT UNTIL 4 PM EDT MONDAY...

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.

   Flash Flood Watch.
   Wind Advisory.

In addition to the threat of heavy rainfall and localized flooding,
isolated to widely scattered thunderstorms will bring a threat of
cloud to ground lightning this evening.

As a warm front shifts north of the region tonight, a line of
showers and embedded strong to severe thunderstorms is expected to
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 between midnight and 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.

GAZ010-140115-
Rabun-
908 PM EDT Sun Apr 12 2020

...FLASH FLOOD WATCH IN EFFECT UNTIL 8 AM EDT MONDAY...
...TORNADO WATCH 113 IN EFFECT UNTIL 2 AM EDT MONDAY...

This Hazardous Weather Outlook is for northeast Georgia.

.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.

   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.

Lane

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