Severe Thunderstorm Warning 68, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1108 AM EDT Mon May 23 2022

.SYNOPSIS...
A cold front will approach the region from the west late today and
likely stall in the region tonight through Monday. As the front
stalls across the region on Tuesday, in situ cold air damming is
poised to develop midweek before a cold front crosses the area
late Thursday.  So, a wet pattern is in store through lateweek,
after which dry high pressure prevails for the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1100 AM EDT Monday: Band of convection is moving across central
SC this morning, with most intense convection mainly to our south,
but some of the stronger convection pushing across our southern
zones. Across the rest of our area, mainly some much-needed rain
with some embedded thunder. Convective trends as per the HRRR show
this initial activity pushing east through the early afternoon with
a secondary band developing closer to the surface low, which is
still to our SW, with that secondary band intensifying later today.
Still some question as to how much the thermodynamics can recover
behind this initial convection, but hi-res guidance all wants to
increase SBCAPEs this afternoon across the Upstate and SW NC
Piedmont to 500 and in some cases upwards of 1000 J/kg. Global
models not so robust, and keeps better activity to our south and
east. Shear certainly not a concern with 40-50kt bulk shear and
>100, almost 200 m2/s2 SRH. So, we'll see how it evolves and if the
thermodynamic environment can recover. HREF updraft helicity on the
12z runs just coming in do have some bullseyes over our eastern
zones so still can't rule anything out, but hopefully this morning's
rain will stabilize the environment just enough.

For now though, again the much-needed rain is welcome but will
monitor the second band for training concerns. Still remain in a
slight risk of excessive rain so flash flooding is a concern
especially along the escarpment but luckily the system is moving;
main concern will be as the system pivots and if a deformation axis
of some sort sets up over the mountains or we get training over an
urban area.

Otherwise...tonight, the main area of heavier precip should lift
northeast through the evening hours, with light showers lingering
well into the overnight. Eventually, and if the sfc low reflection
moves along the effective cool pool/nascent wedge boundary along our
southeast fringe, the real wedge may develop toward daybreak
Tuesday. Confidence modest in how all this will play out, so stay
tuned for changes/upgrades.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 230 AM EDT Monday: Active weather remains in store for much of
the short term, with a washed-out ridge axis well to the east of the
forecast area and broad high pressure setting up over New England
and Quebec.  By Tuesday morning, a stationary front draped across
the Carolinas will provide focus for widespread drizzle and showers,
with isentropic lift atop the surface layer generating precip and
resulting in a stabilized air mass north of the boundary.  This
should further result in the development of an in-situ CAD wedge
by mid-day Tuesday and continued precip changes through the day.
Isentropic lift continues into the overnight but with diminishing
intensity, as the atmosphere becomes increasingly stable.

By Wednesday morning, models depict deep cyclogenesis in the lee
of the Rockies, which enhances warm sector flow even as far east
as the Carolinas.  Meanwhile, as the Z500 height gradient steepens
over the Carolinas, wind speeds increase and the stagnant wedge
boundary begins to lift north, as the slow eastward progression
of the parent high allows the wedge to become increasingly shallow.

Thus, Wednesday afternoon will feature a mixed bag of stratiform
rain/elevated convection north of the lifting warm front, and
surface-based convection south of it.  May also see some terrain
enhancement over the mountains during the evening hours and
overnight, where 925mb flow ticks up in response to the trailing
cold front as it enters the Ohio Valley and the surface cyclone's
warm conveyor belt strengthens.  Difficult to pinpoint an area
on Wednesday evening with greater convective risk; widespread
cloud cover will tend to limit destabilization in some areas,
while others will see much better surface heating and resulting
instability where clouds are able to break up.  Generally went with
shotgun-chance PoPs early Wednesday, then allow PoPs to increase
from west to east late in the day.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 145 AM EDT Monday: Overall not much change to the extended
forecast period.  A robust cold front digs across the forecast area
on Thursday, and although some uncertainty lingers in timing the
FROPA, it looks like some favorable afternoon/evening passage is
more than likely.  GEFS ensembles agree on a good share of sbCAPE
albeit with significant spread (talking anywhere from 800 to 1000+
J/kg) and both the GFS and CMC suggest a stout shortwave traversing
the deeper system out to the west.  Consequently, expect enhanced
lapse rates and a measure of deep layer shear as well - with the
latest GEFS cycle's ensemble mean suggesting a solid 30kts or more
across the Piedmont and Upstate zones.  Thus, a severe threat is
anticipated for Thursday afternoon.

The system's departure remains in question.  Successive GFS runs
have alternately depicted a clean depature with drying taking place
late Thursday versus lingering activity as the upper low deepens
and stalls crossing the Carolinas.  The upper pattern in general
is messy this far out, and global guidance does not have a solid
handle on it.  Generally looks like between Thursday afternoon
and Friday night, the system will finally exit the area, but it's
difficult to narrow things down beyond that with any confidence.
The pattern becomes even more erratic past the weekend, with models
split between a dry start to the workweek or more rainy weather
as moisture flows off the Atlantic and into the region.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
At KCLT and Elsewhere: VFR outside the mtns for the time being...and
most likely through the middle to late part of the morning as the
low clouds are still far to the south and the stronger upglide
has not yet developed. That should change with the arrival of
what looks like a spiral band around a tropical low pressure
system as it moves northeast across the region during the late
morning and early afternoon with moisture surging up from the
south and precip coverage expanding with increasing mid/upper
forcing and isentropic lift. Guidance develops an MVFR ceiling
restriction as the band moves in but it could develop earlier
with occasional light rain showers during the morning. Winds will
remain light, with the direction variable at most places. However,
stronger forcing arrives midday and is expected to bring an area
of heavier rain up from the south and across the region through
the afternoon. This will be handled with prevailing MVFR and
temporary IFR ceiling/vis/thunderstorms as a starting point. More
detail on the timing will be added later. The wind will most
likely come around to NE during this period. After the main band
of heavier rain lifts northward, late in the day the low cloud
ceiling will fall down to IFR and stay that way for the rest of
the period. Eventually, expect LIFR restrictions at all terminals.

Outlook: The stalled frontal boundary and persistent moisture
will keep precipitation and restrictions in the picture through
the middle of the week. Another cold front will arrive from the
west late week. Nocturnal fog/stratus will be possible as well,
especially where rain has recently fallen.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

SYNOPSIS...MPR
NEAR TERM...PM/TDP
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...PM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
554 AM EDT Mon May 23 2022

GAZ010-NCZ033-035-048>053-058-059-062>065-501>507-509-241000-
Rabun-Avery-Alexander-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-
Graham-Northern Jackson-Macon-Southern Jackson-Transylvania-
Henderson-Caldwell Mountains-Greater Caldwell-Burke Mountains-
Greater Burke-McDowell Mountains-Eastern McDowell-
Rutherford Mountains-Polk Mountains-
554 AM EDT Mon May 23 2022

This Hazardous Weather Outlook is for the mountains and foothills of
North Carolina and extreme northeast Georgia.

.DAY ONE...Today and tonight.

A weak low pressure system will bring widespread showers and
thunderstorms to the mountains and foothills today and tonight. The
main threat across the higher terrain will be heavy rain that could
result in localized flash flooding, especially in the few areas that
have had heavy rain in the past few days. Cloud-to-ground lightning
and a few strong wind gusts are also possible.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

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.

GAZ017-018-026-028-029-NCZ036-037-056-057-068>072-082-508-510-
SCZ008>014-019-101>109-241000-
Habersham-Stephens-Franklin-Hart-Elbert-Iredell-Davie-Catawba-Rowan-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
Greater Rutherford-Eastern Polk-Cherokee-York-Anderson-Abbeville-
Laurens-Union SC-Chester-Greenwood-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Central Greenville-Southern Greenville-
Northern Spartanburg-Southern Spartanburg-
554 AM EDT Mon May 23 2022

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

.DAY ONE...Today and tonight.

A weak low pressure system will bring widespread showers and
thunderstorms to the region today and tonight, raising the
possibility of flash flooding and severe thunderstorms. The threat
for heavy rain and localized flash flooding is probably the more
likely of the two because of uncertainty in the amount of instability
we will be able to develop in the atmosphere in the afternoon. Urban
areas will have a higher chance of flash flooding because of the
recent dry spell. If we manage to see any sunshine, particularly
along and south and east of I-85, the prospects for severe
thunderstorms will increase with damaging wind gusts the main threat.
However, if this happens, an isolated tornado will not be ruled out
because of increasing wind shear. Any thunderstorms will bring heavy
downpours of rain and cloud-to-ground lightning. The storms should
taper off by late evening.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

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.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
921 AM EDT Mon May 23 2022

GAZ028-029-SCZ010-011-231400-
Elbert GA-Hart GA-Abbeville SC-Anderson SC-
921 AM EDT Mon May 23 2022

...A strong thunderstorm will impact portions of central Elbert,
southeastern Hart, south central Anderson and southwestern Abbeville
Counties through 1000 AM EDT...

At 921 AM EDT, Doppler radar was tracking a strong thunderstorm 11
miles south of Elberton, or near Nancy Hart State Park, moving north
at 45 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Elberton, Iva, Lake Secession, Starr, Lowndesville, Russell State
Park, Nancy Hart State Park, Middleton, Lake Russell and Fortsonia.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3399 8283 3399 8284 3398 8284 3398 8286
      3400 8288 3401 8290 3441 8283 3437 8252
      3398 8267 3398 8273 3397 8278
TIME...MOT...LOC 1321Z 194DEG 39KT 3395 8280

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

LANE

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1045 AM EDT Mon May 23 2022

SCZ012-019-231530-
Laurens SC-Greenwood SC-
1045 AM EDT Mon May 23 2022

...A strong thunderstorm will impact portions of central Laurens and
central Greenwood Counties through 1130 AM EDT...

At 1044 AM EDT, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Greenwood, or near Lake Greenwood, moving
northeast at 40 mph.

HAZARD...Winds in excess of 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor damage to outdoor objects is
         possible.

Locations impacted include...
Laurens, Greenwood, Clinton, Ninety Six, Joanna, Cross Hill,
Waterloo, Lake Greenwood State Park, Lake Greenwood and Greenwood
State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3422 8216 3463 8193 3460 8191 3459 8189
      3460 8188 3458 8186 3460 8184 3457 8180
      3455 8166 3435 8181 3435 8183 3432 8186
      3430 8190 3424 8191 3421 8194 3420 8194
      3419 8192 3413 8197
TIME...MOT...LOC 1444Z 207DEG 36KT 3426 8203

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

LANE