Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
217 PM EDT Sun Aug 15 2021

.SYNOPSIS...
A surface front will remain nearly stationary across the area
for the next few days.  The remnants of Fred is expected to move
north from the Gulf coast to the Tennessee River Valley Monday night
into mid week. Expect cooler than normal temperatures into mid week.
Abundant tropical moisture will continue across the region through
much of the week leading to areas of heavy rainfall and isolated
strong thunderstorms.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 200 pm: Deep convection, almost exclusively in the form of
showers, has finally bubbled up over the past hour or so, especially
across western NC. Coverage remains mostly isolated, but with slow
destabilization expected to continue, coverage and intensity of the
activity should continue to gradually increase through the afternoon
into the evening. Instability will remain somewhat muted (sbCAPE
generally around 2000 J/kg or less) due to the limited insolation
and warm/moist profiles. Therefore, the severe storm threat
continues to appear limited, but probably non-zero. The larger
concern will remain localized excessive rainfall/possible flash
flooding, primarily this evening, when storm coverage and intensity
is expected to be at its peak.

The moist conditions along with development of a 15-20 kt southerly
flow just above the surface should allow convection to persist
through much of the overnight, although coverage and intensity of
activity and the excessive rainfall potential should steadily
diminish with time. Chances will be highest near the southern
escarpment of the Blue Ridge where upslope lift should be maximized.

Much of Monday should be quite similar to today, with abundant/thick
morning cloud cover slowing insolation and diurnal destabilization.
As such, convection (again, mostly showers), should remain isolated
to widely scattered through mid-afternoon-ish. After that, guidance
generally agrees in lifting a weak mid-level vort max toward the
area within the southerly flow aloft. Additionally, there will be a
bit of an increase in upper divergence late in the day, as an upper
jet max gets its act together a bit more from the TN Valley into the
Great Lakes. Low level flow will also begin to back during this
time, establishing more of a pure upslope regime. While all these
sources of lift will be quite weak, continued high PWATs (around 2")
and moderate instability should allow for development of numerous
showers and storms by early Monday evening. The severe storm threat
will remain limited, but the potential for locally excessive
rainfall and flash flooding will again increase toward the end of
the forecast period. Tonight's min temps will be right around climo,
while Monday's maxes will again be cooler-than-normal...possibly
even a degree or so cooler than today.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 100 PM EDT Sunday: Tropical Storm Fred will be in the
process of making landfall at the start of the short term period
over the FL Panhandle. Model guidance continues to wash away the
low-level center of circulation once Fred surges into the Deep
South during the day Tuesday. With the tropical airmass already
in place, the remnants of Fred will only add to the environment
and PWAT values will surge to near-record values for this time
of year. With a southerly component persistently pumping into the
region, strong WAA will follow and recent trends actually keep the
frontal boundary from dipping fully into the CFWA as previously
thought. Profiles continue to support the idea of hydro issues,
especially when considering all of the rain that as fell or will
fall prior to Tuesday. This includes: a very deep cloud layer,
skinny CAPE, and deep layer saturation through the atmospheric
column. whatever mid-level circulation that is still left from Fred
will likely push into the mountains Tuesday afternoon/evening and
provide a focus of heavy rain across the CFWA, but highlighting
the Blue ridge Escarpment in its path for the heaviest rainfall
amounts, which will increase the landslide threat over the high
country. Model guidance show a wedge-like pattern over the area,
which could enhance the overall rain threat, but the main driver
in terms of a lifting mechanism will be from the frontal boundary
and orographic lift. Hence why the Escarpment will be the area of
concern Tuesday since the highest PWAT values will occur then and
the aforementioned lifting mechanisms will be maximized. Expect
more widespread coverage for flash flooding along the Escarpment
and in locations that receive multiple rounds of showers and
thunderstorms. PoPs will be in the likely/categorical range for
much of the CFWA Tuesday into Tuesday night.

Most of what is left of Fred will push out of the region by
Wednesday as the pattern slowly begins to evolve back into a
typical summertime regime. The airmass will not change much as deep
tropical moisture lingers over the CFWA during the middle part of
the week and still produces the threat for hydro issues. The one
good thing about Wednesday is that the activity will become more
diurnally driven rather than steady precip throughout the daytime
and nighttime periods as we will witness on Tuesday, especially
outside of the mountains. Either way, a very wet pattern will be
in store for the short-term period and will likely cause flash
flooding in portions of the CFWA, especially in poorly drained and
urban areas. High temperatures will run below normal during the
short-term with lots of precip expected and enhanced cloud cover,
but lows will be at or slightly above normal due to extensive
cloud cover.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 200 PM EDT Sunday: The sub-tropical ridge that has been
hanging out over the western Atlantic for a while now will gradually
flatten out and allow the flow aloft to become more zonal by the end
of the week. Model guidance are in better consensus today compared
to yesterday regarding the overall synoptic pattern. This would
suggest that the typical summertime regime will be back in full
force by the upcoming weekend with the usual diurnal convection
trends expected to enter back into the forecast. One difference
is that the models do spit out a few potent shortwaves that would
enhance PoPs to greater than climatology. With the tropical airmass
stubbornly in place through the end of the work week, hydro issues
will persist into at least the first half of the medium range and
could stretch into the second half of the extended if this persists
throughout the week. Global models are showing an upper ridge
building over the southeastern CONUS by the end of the upcoming
weekend, but not fully confident in this change since it is 6+
days out. Temperatures will be below normal through the middle
part of the week, but returning to normal values by the end of
the forecast period.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: MVFR cigs linger this afternoon at KHKY and
the upstate SC terminals. These should lift to VFR by around 20Z.
Otherwise, deep convection is bubbling within a moderately unstable
air mass. Coverage remains isolated at this time, and the more
modest instability (compared with the past couple of days) should
result in just a gradual uptick in intensity and coverage through
the afternoon. As such, we feel comfortable with VCSH/VCTS at most
sites until 21 or 22Z, w/ 4-hour tempos for TSRA thereafter. (Based
on radar trends, tempos begin an hour or two earlier at KHKY and
KAVL). Convective chances will linger through the overnight, but
coverage is forecast to be such that no TAF mention appears
warranted after 06Z or so, at least for now. Cigs are again expected
to lower late tonight into early Monday, with IFR, perhaps LIFR
conditions likely at most sites by sunrise or so. Cigs should then
remain restricted until at least noon or so. Restricted visibility is
also expected, mainly in the mtn valleys, but periods of MVFR are
also possible in other areas.

Outlook: Coverage of mainly afternoon/evening showers and
thunderstorms is expected to remain rather high through mid-week,
with Tue looking like the most active day. A gradual downward trend
in diurnal convection is expected during the latter half of the
week. Widespread low stratus and areas of fog are expected each
morning through at least mid-week.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High  92%     High  81%     Med   74%
KGSP       High  90%     High  85%     Med   71%     High  84%
KAVL       High  94%     Med   70%     High  89%     High  93%
KHKY       High  94%     High  85%     Med   75%     High  82%
KGMU       High  90%     High  80%     Med   68%     High  90%
KAND       High  91%     High  96%     Med   70%     Med   79%

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...JDL
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
520 AM EDT Sun Aug 15 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-160930-
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-
520 AM EDT Sun Aug 15 2021

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

.DAY ONE...Today and tonight.

Scattered to numerous thunderstorms will develop across the western
Carolinas and northeast Georgia this afternoon and linger into the
evening. A few of these storms could become quite strong and produce
large hail, heavy rainfall, and damaging winds.

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

Deep tropical moisture associated with the remnants of tropical
storm Fred will interact with an old front and the mountains to
produce periodic heavy rainfall through the middle part of the week.
The flood threat will steadily increase on Monday as showers and
thunderstorms wet the soil. At this time, the greatest potential for
excessive rain appears to be Tuesday and Tuesday night as a remnant
circulation from Fred moves northward to the west of the region.
This could result in a flash flooding threat, especially in areas
that receive multiple rounds of heavy rainfall.

.SPOTTER INFORMATION STATEMENT...

None.

SBK/PM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
501 PM EDT Sun Aug 15 2021

NCZ033-501-503-505-152130-
McDowell Mountains NC-Caldwell Mountains NC-Burke Mountains NC-
Avery NC-
501 PM EDT Sun Aug 15 2021

...A strong thunderstorm will impact portions of northeastern
McDowell, northwestern Caldwell, Avery and northwestern Burke
Counties through 530 PM EDT...

At 501 PM EDT, Doppler radar was tracking a strong thunderstorm 11
miles south of Newland, or 5 miles southeast of Linville Falls,
moving north at 25 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...
Newland, Banner Elk, Elk Park, Beech Mountain In Avery County,
Crossnore, Sugar Mountain, Seven Devils, Grandfather Mountain State
Park, Linville Falls and B.R. Parkway-Linville Falls To Grandfather.

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 3619 8188 3619 8186 3616 8183 3611 8181
      3611 8178 3591 8171 3587 8177 3582 8192
      3601 8205 3601 8204 3611 8208 3613 8205
      3612 8203 3616 8201 3620 8189
TIME...MOT...LOC 2101Z 158DEG 20KT 3593 8186

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

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
504 PM EDT Sun Aug 15 2021

NCZ082-152130-
Union NC-
504 PM EDT Sun Aug 15 2021

...Strong thunderstorms will impact portions of Union County
North Carolina through 530 PM EDT...

At 504 PM EDT, Doppler radar was tracking strong thunderstorms along
a line extending from 16 miles southeast of Monroe to 7 miles
northeast of Lancaster. Movement was north at 10 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...
Monroe, Indian Trail, Weddington, Stallings, Unionville, Wesley
Chapel, Wingate, Waxhaw, Marshville and Lake Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

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

Frequent cloud to ground lightning is occurring with these storms.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

&&

LAT...LON 3481 8032 3482 8079 3485 8080 3494 8078
      3500 8084 3502 8082 3503 8077 3507 8073
      3515 8055 3518 8037 3517 8036 3519 8028
TIME...MOT...LOC 2104Z 162DEG 8KT 3483 8033 3478 8066

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

HG

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