Severe Thunderstorm Warning 16, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1105 AM EDT Sun Apr 14 2019

.SYNOPSIS...
A strong system will bring more widespread storms to the area on
today and tonight, with severe weather possible. Dry weather
conditions will prevail through mid-week, with showers and
thunderstorms returning at the end of the week with an approaching
cold front.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1100 AM EDT Sunday: Watching closely as instability creeps up
across the Piedmont, with SPC Mesoanalysis indicating 500J/kg SBCAPE
lifting into NC from the western Upstate, and stretching farther
into the NC Piedmont east of I-77. 1000J/kg line creeping into the
Upper Savannah Valley. RAP progs bring a sliver of >2000J/kg into
the Upstate and spread east through the afternoon, and 12z NAM
fairly similar. As mentioned below, shear is impressive, and even 0-
1km shear is pretty high, with RAP/NAM soundings showing a beautiful
curve on hodographs. Will have to see, however, if the RAP/NAM are
correct, as there is some concern that showers moving into the area
from TN/GA may work the environment over this morning (let's hope),
though HRRR still insists on cellular convection developing within
the larger area of showers/embedded thunder. And of course, all the
CAMs are now picking up on QLCS with embedded potential discrete
cells moving across with the actual front into this evening, though
it remains to be seen how well that will hold together across the
area.

Otherwise, potent upper low is moving into MO, with triple point low
surface low pressure across the lower OH Valley, and a cold front
trailing down the Miss Valley. A weak warm front extends through TN
into the southern Appalachians through our forecast area. Expansive
frontal band/warm conveyor belt region covers much of the TN Valley
and will continues to move gradually east through the morning. As
the upper low opens up and kicks out over the eastern Conus later
today into tonight, this area of precip will likely accelerate later
this morning, and is expected to reach the NC mtns by late morning.
Meanwhile, insolation combined with mid-level lapse rates of around
6.5 C/km will result in moderate destabilization across the Piedmont
and much of the foothills this afternoon. Meanwhile, shear will be
more than adequate for organized convection, with deep layer shear
improving to 50+ kts by late this morning, and 0-1km shear of 30-40
kts expected for much of the day. Thus, ingredients should be in
place for an organized severe weather threat.

However, evolution of the threat and mode of convection
remains a subject of some controversy. The NAM and some of its high
resolution relatives have displayed considerable run-to-run
consistency in dissipating the current frontal band across the
southern Appalachians later this morning, before blowing up new
convection within the immediate frontal zone later this morning into
the afternoon. This solution would focus an organized severe weather
threat, most likely in the form of a QLCS for our entire forecast
area from late afternoon through the evening. However, other
high-res guidance, including the HRRR maintain the current frontal
band through the forecast area, intensifying it and focusing the
primary severe threat within the moderately unstable air mass across
the Piedmont during mid/late afternoon.  In this scenario more than
ample effective storm relative helicity would suggest an embedded
mini-supercell threat (such as what is occurring across the MS and
TN Valleys attm). In either scenario, all modes of severe weather,
including isolated tornadoes would be in play. For what it's worth,
we are leaning toward the latter scenario, thinking that the
greatest threat will be across the Piedmont this afternoon. (In this
scenario, convection would also develop along the front proper
during the afternoon/evening, but the severe threat may be limited
with this activity due to instability being overturned by the
morning/afternoon convection. The threat for localized flash
flooding will also increase this afternoon, especially across the
mountains, where this morning's upslope showers is sort of "priming
the pump."

Drier and cooler air will quickly sweep through the area in the wake
of the front this evening, bringing an abrupt end to precip chances,
except along the TN border, where mechanical/upslope lift
associated  with a developing stout NW flow should allow at least
scattered showers to persist through much of the night. With
freezing levels expected to drop to near the ridge tops late
tonight, some light snow may be seen across the highest mountains
after midnight. Min temps are expected to end up in the neighborhood
of normal Monday morning.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 200 AM EDT Sunday: After a weekend of showers and
thunderstorms across northeast GA and the western Carolina, a drying
trend is in store for the short term forecast period as sfc high
pressure builds in from the GOM. However, through early Monday
afternoon, lingering precipitation on the backside of the exiting
system is progged to linger along the TN border. With colder
temperatures infiltrating in behind the recently exited cold front,
precipitation falling may transition to a rain/snow mix, with
flurries/light snow showers possible at the higher elevations. Attm,
no snow accumulation is expected. Elsewhere, conditions will be dry.

A rain-free forecast is on tap for the entire FA on Tuesday with
plenty of sunshine. As sfc high pressure shifts off the Carolina
coast late Tuesday and into the overnight hours, weak upper ridging
across much of the CONUS will eastward and become amplified ahead of
the next approaching system coming out of the Rockies. With
temperatures below normal on Monday behind the recently passed cold
front, a warming trend is expected to begin on Tuesday with
temperatures around normal.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 255 AM EDT Sunday: The dry weather pattern to kick off the
extended forecast period on Wednesday will be short-lived, as latest
guidance continues to come into better agreement on the timing of
another approaching cold front towards end of the work week. Per
latest guidance, with sfc high pressure offshore, sfc low over the
central Plains will continue to strengthen as it very slowly
propagates northeastward towards the Upper Midwest through into
Friday. Aloft, southern stream trough will strengthen and deepen as
it shifts eastward, joining the northern wave energy and becoming an
upper closed low. Nearly expanding across most of the CONUS, the
center of this feature will eject into the upper Midwest into Friday
night, while at the sfc, the parent low's cold front will already be
in the process of pushing eastward through the FA in the morning
hours. Given how far out this feature is, there's still plenty of
time for temporal and spatial changes, but overall anticipate shower
and thunderstorm chances to return as early as Thursday. Ahead of
the front where the Southeast will once again be well in the warm
sector, it'' be another Spring-like system on tap for the last
weekend in April, with dewpoints nearing 60 degrees and high
temperatures on Thursday ranging from the mid 70s to near 80 degrees
south of the I-85 corridor and in and around the Charlotte Metro
area. Behind the exiting system, upper troughing will linger and
swing overhead Saturday and Saturday night, with lingering precip
along the TN border possible, where elsewhere, a drying trend will
be already occurring. Though temperatures will drop to below normal
behind the exiting front, do anticipate temperatures attm to remain
above freezing in the mountains, thus do not anticipate any mention
of snow attm.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: KAVL will continue to be the most showers
likely terminal to see showers this morning, although coverage of
showers should continue to expand to the Piedmont throughout the
morning. Otherwise, IFR/low MVFR cigs will continue through the
morning, with perhaps improvement to higher MVFR or low VFR by
mid/late afternoon.

An area of widespread showers and embedded thunderstorms is forecast
to sweep across the terminal forecast area from late morning through
mid/late afternoon, with categorical -SHRA VCTS and tempos for TSRA
warranted as early as 17Z at KAVL, and as late as 19/20Z at KCLT.
This area of showers and storms will be well ahead of the actual
cold front, and it's looking increasingly likely that a second round
of convection will follow along the front from late afternoon into
the evening. Since the intensity of this activity will depend upon
the intensity of the earlier activity (i.e., how much will the
atmosphere stabilize prior to the second round?), we have generally
handled this with categorical SHRA w/ VCTS and/or Prob30s. Variable
and very gusty winds will be possible with thunderstorms this
afternoon.

Gusty south winds (gusts as high as 30 kts) will develop in advance
of the band of showers later this morning, and continue through much
of the day. Variable and very gusty winds will be possible with
thunderstorms this afternoon. Winds will gradually veer and diminish
in the wake of the cold front, likely becoming W/NW by mid-morning
Monday.

Outlook: Drier westerly winds should help improve flight conditions
behind the front thru Monday morning. VFR conditions should return
early next week behind the cold front, and likely continue through
mid-week.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       High  96%     High  85%     High  95%     High 100%
KGSP       High  98%     Med   77%     High 100%     High 100%
KAVL       High  87%     Med   73%     High 100%     Med   71%
KHKY       High  91%     Med   79%     High  98%     High 100%
KGMU       High  89%     High  87%     High 100%     High 100%
KAND       High  83%     High  83%     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 and ensemble forecasts
are available at the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...High Wind Warning until 10 PM EDT this evening for NCZ033-
     048>052-058-059-062>064.
SC...None.

&&

SYNOPSIS...SGL
NEAR TERM...JDL/TDP
SHORT TERM...SGL
LONG TERM...SGL
AVIATION...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
610 AM EDT Sun Apr 14 2019

GAZ010-017-018-026-028-029-NCZ035>037-056-057-065-068>072-082-
501>504-506>510-SCZ001>014-019-151015-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Alexander-Iredell-
Davie-Catawba-Rowan-Henderson-Cleveland-Lincoln-Gaston-Mecklenburg-
Cabarrus-Union-Caldwell Mountains-Greater Caldwell-Burke Mountains-
Greater Burke-Eastern McDowell-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-Chester-Greenwood-
610 AM EDT Sun Apr 14 2019

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

.DAY ONE...Today and tonight.

Strong to severe thunderstorms are expected today. The primary threat
will be damaging winds, though large hail and isolated tornadoes
cannot be ruled out. Heavy rain may lead to isolated flash flooding,
especially in areas that experience multiple rounds of thunderstorms.

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

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to forward any reports of large hail,
damaging winds, tornadoes, or flash flooding to our office.

NCZ033-048>053-058-059-062>064-505-151015-
Avery-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Graham-
Northern Jackson-Macon-Southern Jackson-Transylvania-
McDowell Mountains-
610 AM EDT Sun Apr 14 2019

...HIGH WIND WARNING IN EFFECT UNTIL 10 PM EDT THIS EVENING ABOVE
3500 FEET...

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.

   High Wind Warning.

Strong to severe thunderstorms are expected today. The primary threat
will be damaging winds, though large hail and isolated tornadoes
cannot be ruled out. Heavy rain may lead to isolated flash flooding,
especially in areas that experience multiple rounds of thunderstorms.

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

No hazardous weather is expected.

.SPOTTER INFORMATION STATEMENT...

Spotters are requested to forward any reports of large hail,
damaging winds, tornadoes, or flash flooding to our office.

SGL

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
122 PM EDT Sun Apr 14 2019

GAZ018-026-028-SCZ004-010-141745-
Hart GA-Franklin GA-Stephens GA-Greater Oconee SC-Anderson SC-
122 PM EDT Sun Apr 14 2019

...A STRONG THUNDERSTORM WILL IMPACT FRANKLIN...SOUTHEASTERN
STEPHENS...HART...WEST CENTRAL ANDERSON AND SOUTHEASTERN OCONEE
COUNTIES UNTIL 145 PM EDT...

At 122 PM EDT, Doppler radar was tracking a strong thunderstorm 8
miles southwest of Carnesville, or 6 miles north of Ila, moving
northeast at 55 mph.

Locations to be impacted include...
Hartwell, Carnesville, Royston, Reed Creek, Lavonia, Gumlog, Canon,
Franklin Springs, Bowersville and Martin.

Wind gusts up to 45 mph will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

A Tornado Watch remains in effect until 700 PM EDT for northeastern
Georgia...and Upstate South Carolina.

LAT...LON 3425 8334 3426 8334 3433 8339 3434 8339
      3467 8303 3443 8269 3424 8309 3427 8312
      3424 8317 3425 8320 3424 8325 3426 8330
      3423 8335
TIME...MOT...LOC 1722Z 231DEG 49KT 3427 8330

RM