Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
156 PM EDT Fri May 19 2017

.SYNOPSIS...
The upper ridge moves east and off the East Coast this weekend as a
closed upper low swings northeast from Colorado. Expect a backdoor
cold front to drop south across the Carolinas Saturday and Saturday
night as a stronger cold front moves east across the Mississippi
Valley. As this cold front moves toward our region over the weekend,
deep moisture from the Gulf will bring an excellent chance
of rain late Sunday into Monday.  Expect another strong system in
mid week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 145 pm: although coverage is about what was expected,
convection fired a little earlier than anticipated across the high
terrain, and was already beginning to move off the Blue Ridge as 18Z
approached. The highest pops were therefore moved earlier in the
day, while they have been increased for much of the NC foothills and
northwest NC Piedmont into the late afternoon. Per the latest SPC
mesoanalysis, the atmosphere is (as expected) decidedly less
unstable and more inhibited for areas roughly along and southeast of
I-85, so will continue to omit pops within that general area.
Moderate levels of shear remain just west of the area, so severe
storms should continue to tend toward the pulse end of the spectrum,
but would not be surprised to see one or two more long-lived cells
as the afternoon wears on.

Otherwise, behind a weak shortwave passage tonight, the upper ridge
will briefly pop back up with a slightly higher amplitude, quickly
helping to shut off convection tonight except for maybe some
isolated activity lingering over the mountains. Temperatures
continue 5-8 degrees above seasonal normals for both highs and lows.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
As of 250 AM Friday: Been looking at this for the last five days
and still not entirely sure what to make of Saturday. The models
have been troubled with how to handle a back-door cold front,
which represents the edge of a cooler and drier air mass centered
over ern Canada. The trend in the guidance for the last 24-36 hrs
has been to hold the cold front to the N/NE of the fcst area, and
now the guidance barely has the boundary making down into the NW
Piedmont. Problem is, in many situations, the models do not handle
well how far to the S/SW these boundaries may ooze, particularly
when precip generated near the boundary helps to reinforce the
cooler air on the N side. The latest model guidance keeps almost
the entire fcst area dry through Saturday, but am not ready to
give up on our fcst that has a chance of precip mainly over NC,
because of the possibility that the boundary may ultimately make it
farther S before stalling/washing out. High temps will be highly
dependent on the boundary position. Have nudged the NW Piedmont
up a few degrees as a hedge against the boundary not making
it. Even if the boundary does, it should wash out Saturday night
and a developing S/SE low level flow should help to force precip
development in the upslope areas near the Blue Ridge Escarpment.

Another trend in the new model guidance is to bring more mid/upper
forcing in from the W/SW earlier on Sunday to act on deepening
Gulf moisture. The new ECMWF is in general agreement that more
widespread precip is likely to develop W to E across the fcst area
on Sunday, such that by the end of the day we have a gradient from
categorical over the wrn part to chance in the I-77 corridor. The
combination of 1000-1500 J/kg of CAPE and shear on the order of
20-25 kt suggests some threat of severe storms, but this is far
from certain. The best forcing will move east across the fcst
area during the overnight hours as a jet streak passes to the
north and the main short wave lifts out of the upper trof still to
our west. Precip prob has been raised into the categorical range
across the entire fcst area. Shear will maximize overnight just
high enough for concern, while CAPE remains fairly low.

Which brings us to Monday. Although the guidance has come into some
agreement with the timing of the passage of the cold front earlier
in the day, there is more indication that precip will linger on
the cooler side of the front longer into the day. As a result,
higher precip chances have been extended into the afternoon farther
to the west. Temps are a bit tricky again as we keep them close
to normal with lingering precip and cloud cover, but an earlier
departure might allow for more recovery if that happens.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 330 AM Friday...any confidence in the passage of a cold
front to our east Monday night, allowing for some drying as weak
high pressure moves in, is quickly dashed by Tuesday as the
models continue to be at odds with how far south the boundary
will make it before stalling and how soon a wave will move along
the front. At least the guidance is consistent from run-to-run,
with the GFS still showing a fairly dry Tuesday while the ECMWF
brings the precip right back in from the SW with a wave during the
day. Will not attempt to reconcile that difference right now, as the
ongoing fcst has increasing precip chances during the day. However,
there is agreement that we will maintain deep moisture and some
forcing through Tuesday night and Wednesday as the next upper trof
swings across the TN valley and southeast. So, instead of showing
a brief lull in activity, it appears more likely that some chance
of precip will continue through the middle part of the week and
the fcst will be adjusted accordingly. The mid- to late-week part
of the fcst looks like it will be dominated by a long-wave upper
trof over the east, which should spell temps being held close to
normal. Few changes were made to the late part of the week.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Scattered convection was firing across the
high terrain early this afternoon, and will move toward KHKY and
remain in the vcny of KAVL for the next couple of hours, warranting
tempos for TSRA at both sites. The bulk of the convection should
remain north of the other terminals, as the air mass is relatively
stable/suppressed across much of Upstate SC and the southern NC
Piedmont. However, there remains enough of a chance at KCLT to
continue the VCSH there, although it has been delayed until 21Z.
Otherwise, VFR conditions are forecast through the period except at
KAVL/KHKY, where rainfall is forecast to fall today, increasing the
odds for at least MVFR visby restrictions early Saturday. Winds will
generally remain SW at 5-8 kts, with variable and gusty winds near
thunderstorms.

Outlook: Diurnal convection will be possible again on Saturday ahead
of a backdoor cold front that approaches the forecast area from the
north. Another front is expected to bring more significant chances
of showers/storms/restrictions Sunday through Monday and possibly
into Tuesday.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High  97%
KHKY       High 100%     High 100%     High  91%     High  97%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     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...PM
NEAR TERM...JDL/TDP
SHORT TERM...PM
LONG TERM...PM
AVIATION...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
631 AM EDT Fri May 19 2017

GAZ010-017-018-026-028-NCZ033-035>037-048>053-056>059-062>065-
068>072-501>510-SCZ001>008-010-201045-
Rabun-Habersham-Stephens-Franklin-Hart-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-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-Anderson-
631 AM EDT Fri May 19 2017

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 by this afternoon
across the mountains and foothills of the Carolinas and northeast
Georgia. Storms will be more isolated along the Interstate 85
corridor. The main threat from the storms will be frequent cloud-to-
ground lightning, heavy downpours, gusty winds, and small hail. A few
of the storms may become severe with large hail and damaging wind
gusts. The storms should diminish in coverage and intensity this
evening after sunset.

.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...

None.

GAZ029-NCZ082-SCZ009-011>014-019-201045-
Elbert-Union-York-Abbeville-Laurens-Chester-Greenwood-
631 AM EDT Fri May 19 2017

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

.DAY ONE...Today and Tonight.

No hazardous weather is expected at this time.

.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...

None.

PM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
110 PM EDT FRI MAY 19 2017

NCZ033-049-050-191745-
Yancey NC-Avery NC-Mitchell NC-
110 PM EDT FRI MAY 19 2017

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
MITCHELL...SOUTHWESTERN AVERY AND NORTHEASTERN YANCEY COUNTIES UNTIL
145 PM EDT...

At 110 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 6 miles north of Burnsville, moving east at 25 mph.

Locations to be impacted include...
Spruce Pine, Burnsville, Bakersville, Bandana, Ingalls, Ramseytown,
Green Mountain, Minneapolis, Micaville and Poplar.

In addition to intense lightning, wind gusts up to 40 mph and dime
size hail will be possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3588 8199 3587 8200 3588 8201 3588 8202
      3586 8203 3585 8205 3592 8240 3610 8237
      3611 8210 3610 8208 3611 8208 3611 8196
TIME...MOT...LOC 1710Z 276DEG 20KT 3601 8230

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
116 PM EDT FRI MAY 19 2017

NCZ065-507-509-191745-
Henderson NC-Polk Mountains NC-Rutherford Mountains NC-
116 PM EDT FRI MAY 19 2017

...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL RUTHERFORD...
NORTHEASTERN HENDERSON AND WESTERN POLK COUNTIES UNTIL 145 PM EDT...

At 115 PM EDT, Doppler radar was tracking a strong thunderstorm near
Hendersonville, or near Mountain Home, moving east at 25 mph.

Locations to be impacted include...
Hendersonville, Fletcher, Flat Rock, Mountain Home, Laurel Park,
Saluda, Chimney Rock State Park, Bat Cave, Asheville Airport and
Mills River.

Wind gusts up to 40 mph and half inch hail will be possible in these
areas.

LAT...LON 3547 8213 3543 8216 3539 8220 3529 8229
      3522 8227 3528 8257 3542 8255 3543 8254
      3543 8253 3545 8253 3545 8247 3546 8244
      3547 8226 3546 8225 3547 8225
TIME...MOT...LOC 1715Z 276DEG 20KT 3537 8247

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
120 PM EDT FRI MAY 19 2017

NCZ503>506-191745-
McDowell Mountains NC-Burke Mountains NC-Greater Burke NC-
Eastern McDowell NC-
120 PM EDT FRI MAY 19 2017

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL MCDOWELL AND
SOUTHWESTERN BURKE COUNTIES UNTIL 145 PM EDT...

At 119 PM EDT, Doppler radar was tracking a strong thunderstorm 5
miles northwest of Marion, moving east at 20 mph.

Locations to be impacted include...
Marion, Lake James State Park, Lake James, Table Rock, Old Fort, B.R.
Parkway-Craggy To Little Switzerland, Nebo, Pleasant Gardens,
Woodlawn and North Cove.

Wind gusts up to 40 mph and dime size hail will be possible in these
areas.

LAT...LON 3560 8179 3563 8217 3576 8218 3578 8216
      3579 8217 3580 8216 3580 8215 3581 8215
      3582 8214 3587 8181
TIME...MOT...LOC 1719Z 266DEG 16KT 3572 8209

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
145 PM EDT FRI MAY 19 2017

NCZ505-506-191815-
McDowell Mountains NC-Eastern McDowell NC-
145 PM EDT FRI MAY 19 2017

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT SOUTHERN
MCDOWELL COUNTY UNTIL 215 PM EDT...

At 144 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning near Marion, moving southeast at 20 mph.

Locations to be impacted include...
Marion, Old Fort, Lake James, Nebo, Sugar Hill, Pleasant Gardens,
Glenwood, Fero, Dysartsville and Thermal City.

In addition to intense lightning, wind gusts up to 40 mph, dime size
hail and very heavy rainfall rates up to 2 inches per hour will be
possible in these areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent lightning is occurring with this storm. If outdoors, try to
get indoors or into a hard topped vehicle. Otherwise, stay away from
open areas and isolated high objects such as trees. When indoors,
stay away from windows and doors and avoid using wired electronic
devices. Do not take a shower or bath. Try to unplug unnecessary
appliances before the storm approaches.

&&

LAT...LON 3571 8186 3558 8182 3554 8185 3552 8197
      3553 8197 3555 8200 3554 8203 3554 8206
      3563 8219 3578 8207
TIME...MOT...LOC 1744Z 302DEG 17KT 3567 8206

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
216 PM EDT FRI MAY 19 2017

NCZ505>508-191845-
Greater Rutherford NC-McDowell Mountains NC-Eastern McDowell NC-
Rutherford Mountains NC-
216 PM EDT FRI MAY 19 2017

...STRONG THUNDERSTORMS WILL IMPACT SOUTHEASTERN MCDOWELL AND
NORTHERN RUTHERFORD COUNTIES UNTIL 245 PM EDT...

At 216 PM EDT, Doppler radar indicated strong thunderstorms along a
line extending from near Marion to 14 miles northwest of
Rutherfordton, and moving east at 10 mph.

Locations to be impacted include...
Marion, Rutherfordton, Chimney Rock State Park, Green Hill, Thermal
City, Glenwood, Union Mills, Shingle Hollow, Sugar Hill and Fero.

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

LAT...LON 3571 8186 3558 8182 3558 8180 3559 8179
      3559 8177 3561 8176 3560 8173 3533 8198
      3546 8225 3550 8222 3551 8223 3552 8222
      3553 8217 3555 8220 3572 8205
TIME...MOT...LOC 1816Z 287DEG 11KT 3565 8202 3552 8214

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
221 PM EDT FRI MAY 19 2017

NCZ063-064-SCZ001-191845-
Transylvania NC-Southern Jackson NC-Oconee Mountains SC-
221 PM EDT FRI MAY 19 2017

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN TRANSYLVANIA...
SOUTHEASTERN JACKSON AND NORTH CENTRAL OCONEE COUNTIES UNTIL 245 PM
EDT...

At 221 PM EDT, Doppler radar was tracking a strong thunderstorm 18
miles southeast of Franklin, or 4 miles south of Cashiers, moving
southeast at 20 mph.

Locations to be impacted include...
Cashiers, Gorges State Park, Lake Jocassee, Highlands, Sapphire, Bad
Creek and Whiteside Mountain.

Wind gusts up to 40 mph and dime size hail 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. Do not drive across
flooded roads.

&&

LAT...LON 3508 8316 3508 8314 3510 8315 3516 8311
      3510 8283 3506 8287 3505 8291 3503 8292
      3501 8292 3501 8293 3492 8301 3496 8312
      3499 8310 3502 8313 3504 8313 3506 8317
TIME...MOT...LOC 1821Z 299DEG 15KT 3505 8309

HG