Hail in Georgia, April 25, 2020

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
535 PM EDT Sat Apr 25 2020

.SYNOPSIS...
A compact but energetic storm system will move from Kentucky to
Pennsylvania tonight into Sunday as its showers and thunderstorms
eventually exit our region.  Seasonably cool conditions are expected
behind this system with the next shot at widespread rain arriving by
the middle of the week.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 525 PM: Forecast for the near term still extremely
complicated. The first factor of concern is the slight risk
encompassing most of the NC mountains, Upstate SC, and the
NC Piedmont. This still appears to fit well with the area of
greatest severe risk, focusing mainly on the evening hours. With
many factors in play, however, there exists some uncertainty in the
most likely severe threat and exactly where each type of threat will
evolve. Have tried to refine timing of peak threat with this update.

A robust upper wave and surface low are in the process of
propagating towards the area this afternoon, with a warm frontal
boundary now across the southern CWA. With high pressure to our
northeast shifting off the NE coast, the wedge-like pattern that has
been in place for much of today is eroding across the area. Surface
flow has been generally NErly for much of the day, though, which
has limited low-level moistening, and dew points will likely
only be able to peak in the mid 50s later this evening with the
anticipated shift to Srly/SWrly flow over the next hour or so. The
lack of robust surface moisture will likely be a large factor in
limiting surface destabilization, as will the late-day clearing.

Despite this, there is no shortage of favorable factors for
severe weather. Deep-layer shear across the area is already on
the order of approx 50kt, and both directional and speed shear
(especially in low levels) will increase through the afternoon as
surface flow veers to S-SWrly. Additionally, a 500mb speed max is
on approach towards the southern Appalachians, and the arrival of
an upper jet exit region will encourage plentiful upper forcing
later this evening, close to 00Z. The sharpening upper trough
aloft over the southeast will also decrease temperatures aloft,
manifesting in steep mid-level lapse rates this evening. Despite
SBCAPE likely limited to 500-1000 J/kg, MLCAPE could exceed 1000
J/kg. With the excellent shear and sufficient CAPE, the mode
of convection will likely end up supercellular, with supercells
embedded in a squall line crossing the northern 2/3 of the forecast
area from 23Z-04Z this evening looking like the most likely final
outcome. NAMNest appears to be doing a decent job of handling
the activity now over East TN, and PoPs have been tilted in that
favor. All severe threats are in play, though hail rises to the
top as the most likely threat with cool, dry air entering aloft
and excellent lapse rates expected. The potential for wind damage
(especially if convection can become at all linear) and for an
isolated tornado (despite the lack of boundary layer moisture,
which keeps LCL heights questionable) is still in play. It should
also be noted that while the best forcing will be in place across
the northern 2/3 of the forecast area and the greatest severe
threat overall is there, the warm front lifting northward from
the Midlands should be watched, especially for tornado potential
as it locally enhances low-level SRH and boundary layer moisture.

If you've made it this far, the good news is that the convection
should clear our area by 05-06Z overnight, though some NW flow
and wrap-around moisture will enhance shower activity in the
mountains near daybreak tomorrow. Some moisture may even break
containment, with showers possible across the majority of the NC
mountains tomorrow, not just the TN/NC border. Though no accums
are forecast at the current time, temperatures will drop enough
tomorrow as upper heights drop that some light snow may be possible
at elevations above 5000ft. the other story across the area will
be wind - stout NW flow will encourage gusts up to 25+ mph outside
the mountains, and up to 35+ mph in the mountains. Temperatures
will be below average.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 215 PM Saturday: An upper trough axis crosses the area Sunday
night then moves east through the rest of the short term with slowly
rising heights as an upper ridge axis moves in by Tuesday. Deep NW
flow, short waves, and upper divergence will act on lingering
moisture over the mountains to keep showers there Sunday night.
Temps may be cold enough for some very high elevation snow, but p-
type will be rain for the vast majority. gusty NW wind will remain
over the area Sunday night into Monday. Gusts as high as 40 mph will
be possible across the higher elevations with gusts to 30 mph
possible elsewhere. A weak clipper-type system approaches from the
NW on Tuesday but weakens as it moves toward the area. Have kept the
forecast dry for now. Temps will be a few degrees below normal
Sunday and Monday nights and on Monday then warm a few degrees above
normal for Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 225 PM Saturday: An upper low moving across the Great Lakes
will swing a strong short wave trough across our area Wednesday and
Wednesday night. The associated cold front moves in during the same
time frame. There will be good forcing and deep moisture, but only
weak instability. Guidance is in good agreement on timing and PoP
has increased to high likely and categorical on Wednesday with
likely PoP Wednesday night. Agree with previous shift that since
it's late April and still 5 days out, we won't rule out anything in
terms of the severe convective potential at this point, but
hazardous weather is not looking like a slam dunk either. There will
be some lingering NW flow rain showers Thursday and possibly Friday
then dry on Saturday.

Near normal temps Wednesday drop a few degrees Thursday, then back
to near normal Friday and above normal on Saturday.

&&

.AVIATION /22Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Winds will continue to take on a southerly
direction through this afternoon and evening ahead of an approaching
storm system. MVFR clouds will generally prevail through this
evening, though a brief rise to VFR may occur as a few spots are
able to scatter out this afternoon. A line of showers and
thunderstorms, some with gusty winds, will cross the area from west
to east between 23Z and 05Z this evening, bringing brief cig and vis
restrictions as it passes. In the wake of the storms, cigs will lift
back to VRF in the early morning hours, and winds will become NWrly
for tomorrow, with gusts developing in the afternoon hours.

Outlook: After the storms tonight pass, generally VFR conditions
will prevail through Tuesday before another storm system bring rain
chances and restrictions back on Wednesday.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High  91%     High  86%     High 100%     High 100%
KGSP       High  96%     High  98%     High 100%     High  98%
KAVL       High  85%     High  86%     High 100%     High  94%
KHKY       High  95%     Med   65%     High  98%     High  96%
KGMU       High  95%     High 100%     High 100%     High  98%
KAND       High 100%     High 100%     High 100%     High  98%

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...None.
SC...None.

&&

SYNOPSIS...DEO
NEAR TERM...17/08
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...17

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
623 AM EDT Sat Apr 25 2020

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-261030-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Iredell-Davie-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-
Rowan-Graham-Northern Jackson-Macon-Southern Jackson-Transylvania-
Henderson-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
Caldwell Mountains-Greater Caldwell-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-Cherokee-York-
Anderson-Abbeville-Laurens-Union SC-Chester-Greenwood-
623 AM EDT Sat Apr 25 2020

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

.DAY ONE...Today and tonight.

Scattered thunderstorms are expected to develop across the area
along and ahead of a cold front from late this afternoon through the
evening. A few of these storms will have the potential to produce
severe weather, primarily in the form of damaging wind gusts and
large hail. However, an isolated tornado cannot be ruled out.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

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.

Lane

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
533 PM EDT Sat Apr 25 2020

GAZ010-017-252200-
Rabun GA-Habersham GA-
533 PM EDT Sat Apr 25 2020

...A STRONG THUNDERSTORM WILL IMPACT NORTHERN HABERSHAM AND WESTERN
RABUN COUNTIES UNTIL 600 PM EDT...

At 532 PM EDT, Doppler radar was tracking a strong thunderstorm 7
miles north of Clarkesville, moving northeast at 20 mph.

Locations to be impacted include...
Clayton, Tiger, Tallulah Falls, Lake Rabun, Lake Burton, Lakemont,
Tallulah Gorge State Park, Black Rock Mountain State Park, Batesville
and Seed Lake.

Wind gusts up to 40 mph and pea size hail 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.

Lake Rabun and Lake Burton are in the path of this storm. Cloud to
ground lightning and gusty winds will create dangerous boating
conditions. Move to shore immediately.

&&

LAT...LON 3482 8365 3484 8366 3488 8366 3490 8363
      3491 8363 3492 8360 3494 8360 3495 8355
      3499 8355 3482 8330 3472 8336 3464 8359
      3468 8365 3471 8364 3473 8362 3476 8363
      3480 8368
TIME...MOT...LOC 2132Z 225DEG 19KT 3471 8357

MOORE