Wind Advisory 10, NWS Greenville-Spartanburg, SC

873 
WWUS72 KGSP 012155
NPWGSP

URGENT - WEATHER MESSAGE
National Weather Service Greenville-Spartanburg SC
555 PM EDT Fri Sep 1 2017

NCZ051-052-058-059-062-063-012300-
/O.EXP.KGSP.WI.Y.0010.000000T0000Z-170901T2200Z/
Swain-Haywood-Graham-Northern Jackson-Macon-Southern Jackson-
Including the cities of Alarka, Almond, Bryson City, Luada, 
Wesser, Waynesville, Waterville, Canton, Cruso, Cove Creek, 
Robbinsville, Stecoah, Cullowhee, Tuckasegee, Sylva, Franklin, 
Rainbow Springs, Kyle, Highlands, Wolf Mountain, and Cashiers
555 PM EDT Fri Sep 1 2017

...WIND ADVISORY WILL EXPIRE AT 6 PM EDT THIS EVENING...

Winds will continue to diminish this evening falling below wind
advisory levels. However, gusty winds will continue into Saturday. 

$$

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
705 AM EDT Fri Sep 1 2017

.SYNOPSIS...
Numerous rounds of showers and thunderstorms are expected through
late tonight as the remnants of Harvey move into the Ohio Valley
and a frontal boundary persists across Western North Carolina.
Warmer and drier high pressure behind Harvey will result in a return
to near normal temperatures by early next week. A cold front will
approach from the west by the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 630 AM EDT Friday: Updates this morning are mainly to tweak
pops (some increases here, some decreases there), but overall
parameters looking fairly similar to earlier, though the 06z runs of
most guidance have bumped up sbCAPE values, over 2000 J/kg in SE
zones. SPC mesoanalyses show over 500 J/kg stretching into portions
of the Upper Savannah Valley already. Latest runs of the HRRR have
been increasingly indicating more discrete cells...which is not a
trend we want to see.

Otherwise, circulation center of the remnants of Harvey is located
in Middle TN (W of Nashville) currently, and will move up the
western side of the Appalachians through the period. Upper low will
continue to move E over the Canadian Maritimes, as Atlantic ridging
remains in places and continues to push up toward the Mid-Atlantic
between the two lows. Resulting confluent flow over the eastern
Great Lakes will allow a surface high to continue to push east and
ridge down the Eastern Seaboard, though its southwestward progress
will be halted by the lifting remnants of Harvey.

The result is a small area of enhanced concern across the Piedmonts
of NC/SC (and naturally our focus is generally over the western
Piedmont) where the moisture from Harvey will lift and intersect the
"wedge" boundary, draped somewhere over NC, around the I-40
corridor, collocated with plenty of synoptic lift in the form of
increasing PVA and upper jetlet forming around the SE side of the
Harvey upper low with associated jet-level dynamics. Low-level flow
will back to the SE east of the mountains, creating anomalously
favorable hodographs (for September that is...though anything's
possible when you have the remnants of a tropical system nearby),
and LLJ of up to 40kt helps to increase the speed shear. Mid-level
lapse rates with the cooling aloft will be tempered by an inversion
between 500-700mb with some low/mid-level WAA on the SE side of the
Harvey upper low. Plentiful deep-layer moisture in place with PWs
maximizing at almost 2", and with instability in the warm sector of
1000-1500 J/kg (note this is lower than earlier runs), tempered by
widespread cloud cover this morning, we could be looking at a fairly
interesting day. NAM, as usual, has higher CAPE values (spreading
the instability farther north) and a little more curvature to the
hodographs, but all near-term guidance shows some curving to the
hodographs, especially closer to I-77. Hires reflectivity guidance
all point to semi-discrete cells developing off the escarpment by
midday, maybe 18z at the latest, trucking east toward the I-77
corridor by 20-21z, and generally out of our area by 00z, with just
some showery activity remaining. SPC Day1 outlook keeps a good chunk
of the area along and S of I-40 in the Slight Risk; given the
lowering trends in sbCAPE, this seems absolutely reasonable (vs.
Enhanced). Damaging winds and isolated tornadoes continue to be the
main threats with these storms.

For now, the heavy rain threat looks minimized, or at least not
widespread. Certainly any of these storms that develop would be
efficient rainfall producers, but they will be moving at a decent
clip with the flow aloft. Biggest concern would likely be around the
Charlotte Metro area, maximized this afternoon/evening as the
convection moves through. Basin-average QPF for the day looks to be
1-1.5" along the I-77 corridor (locally higher amounts). Precip will
exit rapidly from the SW as Harvey's remnants continue to lift NE,
and by the end of the period, expect only some lingering showers
across the northern tier and possibly the mountains (associated with
the upper low itself).

Temperatures have some bust potential today, dependent on the
location of the boundary/stationary front (whether it's north or
south of I-40), cloud cover, and how quickly convection develops.
For now, a good 6-8 degrees below seasonal normals for highs today,
and pretty close to normal for lows tonight.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 250 AM EDT Friday: the short term fcst picks up at 12z on
Saturday with the remnant upper low of Harvey just to our west and
another upper trof digging down across the Western Great Lakes.
As we go into Sunday, the remnants of Harvey will be absorbed by
the above mentioned upper trof as steep upper ridging persists
across the Western CONUS. By late Sunday/early Monday, heights
will have begun to recover as the upper trof lifts NE of the area.
At the sfc, the remnant low that was TS Harvey will be nearly
co-located with the upper low with high pressure centered NE of
the low. Over the next 24 hrs or so, the low will lift well north
of the area and drier high pressure will settle over the CWFA in
its wake. This drier airmass is expected to remain over the area
into early next week. As for the sensible wx, I kept the lingering
PoPs over the fcst area on Sat with a dry fcst for most of Sun,
onward. Temps will start out a few degrees below normal on Sat
and warm to near normal on Sun.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 245 AM EDT Friday: the extended fcst picks up at 12z on Labor
Day with persistent upper ridging over the Western CONUS and a very
broad upper trof beginning to dig down across the Great Lakes. Over
the next couple of days, the trof digs far southward and towards the
fcst area. As the trof axis approaches the CWFA late Wed/early
Thurs, the long range models spin off an upper low from the southern
tip of the trof. At the sfc, broad high pressure will be over the
region to start the period as the remnants of Harvey are finally
making their way off the New England Coast. As we go into Tues, the
Bermuda High will strengthen to our east as the low-lvl flow becomes
SLY again. In addition, a cold front will approach the CWFA later in
the day and stall out over the fcst area on Wed. High pressure
behind the front tries to overspread the area by the end of the
period, however it's unclear at this point whether or not the high
will be able to actually spread far enough eastward before it
weakens. As for the sensible fcst, PoPs will ramp up on Tues and
remain elevated thru the rest of the period. Temps will start out
right around climatology and cool well below climo for Wed and
Thurs.

&&

.AVIATION /11Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: Generally IFR cigs across the area at TAF
time, with some pockets of LIFR (especially across the Upstate) and
holes of MVFR. Should see a slow lifting trend through the morning
hours but with instability increasing with the approach of the
remnants of Harvey, with convection expected area-wide this
afternoon. Have timed most significant TSRA with VRB20G30KT at KCLT
between 20-00z this evening, slightly earlier for other TAFs. May
see some lingering restrictions before clearing starts to move in
after 06z. Winds SE to start the period, possibly backing more ESE
this morning ahead of the approaching low, then veering again toward
S and SSW by the end of the period. Speeds should generally be 5-
10kt but cannot rule out some low-end gusts, and of course more
significant gusts in TSRA.

Outlook: Mountain and northern tier scattered showers may linger on
Saturday, with marginal improvement through Sunday, but with low
level moisture likely remaining. Drier weather is expected on Monday.

Confidence Table...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       Med   64%     Med   73%     High 100%     High  94%
KGSP       Med   69%     High  85%     High 100%     High 100%
KAVL       High  83%     Med   78%     Med   70%     Med   71%
KHKY       Med   69%     High 100%     High 100%     Med   69%
KGMU       High  89%     High  90%     High 100%     High 100%
KAND       Med   66%     High  80%     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...None.
SC...None.

&&

SYNOPSIS...JPT
NEAR TERM...TDP
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...TDP

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
543 AM EDT Fri Sep 1 2017

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-020945-
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-
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-Chester-Greenwood-
543 AM EDT Fri Sep 1 2017

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

.DAY ONE...Today and Tonight.

Severe weather possible. The moisture from the remnants of Harvey
coupled with strong winds aloft and an unstable atmosphere, will
increase the potential for severe thunderstorms. The primary threats
will be damaging straight-line winds and isolated tornadoes. Isolated
activity could begin late Friday morning roughly along and south of
Interstate 85, with a greater potential Friday afternoon and evening
over the entire region. There is also a lingering heavy rain threat,
thus flooding and flash flooding are possible.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

..Saturday...No hazardous weather is expected at this time.
..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

JPT