Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
249 PM EDT Tue Jul 27 2021

.SYNOPSIS...
A weak stationary front from west to east across our region will
slowly dissipate into mid week. Hot and dry high pressure will
prevail from Wednesday until Friday when a cold front arrives from
the north. Expect mainly afternoon showers and thunderstorms during
the weekend. Another cold front should arrive from the north to
start next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 200 PM EDT Tuesday: Convection has begun to break out,
mainly across the NC mountains.  A few cells have begun to shift
east of the Blue Ridge Escarpment much as anticipated.  A weak,
increasingly diffuse frontal zone is draped across the southern
SC Upstate, south of I-85.  Although this morning's fog and a
persistent high-level ceiling over parts of the lower Piedmont
initially hindered destabilization, SBCAPE has still managed to
crest 2500 J/kg across most of the CWA.  Categorical PoPs are
forecast across the mountains this afternoon and into the early
evening, with likely PoPs stretching across Upstate and Piedmont.
Expecting to see convection initiation here within the next hour
or two.

Although instability isn't quite what it was yesterday, a handful
of pulse severe storms cannot be ruled out, particularly across the
southern tier of the CWA.  The larger concern, however, will once
again be locally excessive rainfall.  Model profiles indicate warm
cloud depths of at least 10-11 kft for much of the afternoon, and
although MBE vectors are a hair larger than they were yesterday,
they're still small enough to warrant a risk of localized flash
flooding.  Moreover, some areas have been primed by yesterday's
rainfall such that it will not take much precipitation to push them
into risky territory.  CAMs have significantly dialed back the
overall coverage of convection, with the latest HRRR and NAMnest
in particular being unimpressed by the setup.  Still, several
models keep scattered showers and storms in the forecast through
perhaps 01-02Z, at which point stabilization and dry northerly
flow inhibit further convection.

Overnight, the upper levels experience significant drying,
paving the way for intense radiational cooling.  Thus, tomorrow
morning carries another chance of some fog or low stratus, though a
less-saturated boundary layer and somewhat steadier surface winds
should keep it becoming as dense or persistent as this morning's
event.  Instead, low clouds will scatter out within the first hour
or two after sunrise, giving way to clear, dry weather leading into
the late morning.  With this drying, CCLs will be considerably
higher tomorrow afternoon than they have been the last two days.
Although some convection isn't out of the question, fairly confident
it won't be as widespread or intense as we have seen in recent days.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 225 PM EDT Tuesday: the short-term forecast picks up at 00z
on Thursday with broad upper trofing centered over the NE CONUS
and steep upper ridging still in place over the rest of the CONUS.
This pattern is expected to persist thru the period and into the
extended. At the sfc, weak high pressure will be centered over our
area as the period begins late Wed/early Thurs with a moist frontal
bndy to our south. Another weak cold front will track out of the
Ohio Valley on Thursday and drop into our CWA late Thurs/into early
Friday. The front will be slow to move thru the fcst area, with most
of the latest guidance placing the bndy over our southern tier of
zones (or just south of them), as the period ends Friday evening.
As for the sensible fcst, broad subsidence should keep things dry
on Thursday with more typical summertime PoPs returning for Friday.
Temps will remain well-above climo thru the period with triple digit
heat indices likely across most of the lower terrain both days.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 205 PM EDT Tuesday: the extended forecast picks up at 00z
on Saturday with broad upper trofing centered over New England
and steep upper ridging still in place over the west. This pattern
is expected to persist through the period with the upper trof
amplifying again early next week and shifting at least slightly
west. At the sfc, a weak frontal bndy and associated lee trof will
be lingering somewhere just to our south as the period begins.
Most of the long-range guidance has the bndy lifting back to the
north gradually over the weekend. By early next week, broad high
pressure from Canada will push southward and move over the Great
Lakes as the period ends. This will likely provide some drying at
least across our northern zones, however the above-mentioned moist
bndy will persist just to our south and may shift back northward
as the period ends. Temps will start out just above climatology
on Sat, and cool to below climo by early next week.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Scattered convection has begun to break
out across the NC mountains and is already pushing east off the
Blue Ridge Escarpment.  Expecting some convection across the SC
Upstate as well later this afternoon, warranting VCTS and TEMPOs for
TSRA at all sites into this evening.  Variable winds will continue
overnight, before becoming light and northeasterly by early morning.
Restrictions should develop again tonight as dry air pushes in at
upper levels and permits fog to form in the hours before sunrise.
This fog is expected to be less dense and shorter-lived than
what we saw this morning - most sites only drop to MVFR, while
KAVL may have IFR ceilings for an hour or two.  Any fog or low
stratus that does form should dissipate quickly after sunrise.
Tomorrow afternoon, convection will be inhibited compared to
previous days, and although a couple of convective cells cannot
be ruled out, confidence is growing that it should be much less
pronounced than the last few days.

Outlook: Continued dry air influx suggests the lull in convective
activity will extend into Thursday, before a return to the usual
summertime pattern revives diurnal showers and storms on Friday.
This trend continues through the weekend.  Early morning fog and low
stratus will once again be possible each morning from Friday onward.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High  98%     High  99%
KGSP       High 100%     High 100%     High  91%     High 100%
KAVL       High 100%     High  95%     Low   54%     High  85%
KHKY       High 100%     High 100%     High  87%     High 100%
KGMU       High 100%     High 100%     High  87%     High 100%
KAND       High 100%     High 100%     High  83%     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...None.
NC...None.
SC...None.

&&

SYNOPSIS...DEO
NEAR TERM...MPR
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...MPR

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
440 PM EDT Tue Jul 27 2021

GAZ010-017-NCZ033-048>053-058-059-062>065-501>507-509-282045-
Rabun-Habersham-Avery-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-
440 PM EDT Tue Jul 27 2021

This Hazardous Weather Outlook is for northeast Georgia and western
North Carolina.

.DAY ONE...Tonight.

Widespread showers and thunderstorms can be expected again this
afternoon into this evening. The main hazards are cloud-to-ground
lightning, heavy downpours leading to potential for flooding or
flash flooding, and the potential for isolated strong to severe
storms. Damaging wind gusts are possible with any storm that becomes
strong to severe.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

GAZ018-026-028-029-NCZ035>037-056-057-068>072-082-508-510-SCZ001>014-
019-282045-
Stephens-Franklin-Hart-Elbert-Alexander-Iredell-Davie-Catawba-Rowan-
Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
Greater Rutherford-Eastern Polk-Oconee Mountains-Pickens Mountains-
Greenville Mountains-Greater Oconee-Greater Pickens-
Greater Greenville-Spartanburg-Cherokee-York-Anderson-Abbeville-
Laurens-Union SC-Chester-Greenwood-
440 PM EDT Tue Jul 27 2021

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

.DAY ONE...Tonight.

Widespread showers and thunderstorms can be expected again this
afternoon into this evening. The main hazards are cloud-to-ground
lightning, heavy downpours leading to potential for flooding or
flash flooding, and the potential for isolated strong to severe
storms. Damaging wind gusts are possible with any storm that becomes
strong to severe.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Heat indicies will climb into the low hundreds Wednesday through
Friday due to temperatures in the mid to upper 90s combined with high
humidity. These will be the warmest heat index conditions seen so far
this year, which could cause stress to those working in the heat or
without access to air conditioning.

.SPOTTER INFORMATION STATEMENT...

None.

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
531 PM EDT Tue Jul 27 2021

NCZ035-036-272200-
Iredell NC-Alexander NC-
531 PM EDT Tue Jul 27 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN ALEXANDER AND
NORTHWESTERN IREDELL COUNTIES UNTIL 600 PM EDT...

At 531 PM EDT, Doppler radar was tracking a strong thunderstorm 11
miles northeast of Taylorsville, or near Love Valley, moving
southeast at 15 mph.

Locations to be impacted include...
Love Valley, Vashti and Union Grove.

Wind gusts up to 40 mph, pea size hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

LAT...LON 3605 8085 3599 8080 3588 8104 3602 8117
      3604 8113 3604 8111 3603 8110 3603 8107
      3606 8098
TIME...MOT...LOC 2131Z 319DEG 15KT 3603 8103

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
601 PM EDT Tue Jul 27 2021

NCZ035-036-272230-
Iredell NC-Alexander NC-
601 PM EDT Tue Jul 27 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN ALEXANDER AND
NORTHWESTERN IREDELL COUNTIES UNTIL 630 PM EDT...

At 601 PM EDT, Doppler radar was tracking a strong thunderstorm 9
miles east of Taylorsville, or near Love Valley, moving south at 5
mph.

Locations to be impacted include...
Stony Point, Love Valley and Hiddenite.

Wind gusts up to 40 mph, half inch hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

LAT...LON 3602 8109 3605 8100 3590 8086 3584 8107
TIME...MOT...LOC 2201Z 340DEG 5KT 3597 8102

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
614 PM EDT Tue Jul 27 2021

NCZ035-272245-
Alexander NC-
614 PM EDT Tue Jul 27 2021

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL ALEXANDER COUNTY UNTIL
645 PM EDT...

At 613 PM EDT, Doppler radar was tracking a strong thunderstorm near
Taylorsville, moving south at 10 mph.

Locations to be impacted include...
Taylorsville, Millersville, Ellendale and Little River In Alexander
County.

Wind gusts up to 40 mph, pea size hail and very heavy rainfall rates
up to 2 inches per hour will be possible in these areas.

LAT...LON 3601 8122 3598 8112 3584 8116 3589 8131
TIME...MOT...LOC 2213Z 018DEG 8KT 3594 8120

KRENTZ

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
623 PM EDT Tue Jul 27 2021

NCZ035-502-504-272300-
Greater Burke NC-Greater Caldwell NC-Alexander NC-
623 PM EDT Tue Jul 27 2021

...A CLUSTER OF THUNDERSTORMS WILL IMPACT SOUTHWESTERN ALEXANDER...
SOUTHEASTERN CALDWELL AND CENTRAL BURKE COUNTIES UNTIL 700 PM EDT...

At 622 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 5 miles northwest of
Taylorsville to 4 miles northwest of Morganton, and moving southwest
at 15 mph.

Locations to be impacted include...
Lenoir, Morganton, Sawmills, Granite Falls, Valdese, Gamewell,
Bethlehem, Hudson, Cajah's Mountain and Drexel.

Wind gusts up to 40 mph, pea size hail and very heavy rainfall rates
up to 2 inches per hour 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.

&&

LAT...LON 3599 8126 3582 8125 3566 8178 3584 8176
TIME...MOT...LOC 2222Z 023DEG 15KT 3596 8127 3580 8173

KRENTZ

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