Severe Thunderstorm Warning 246, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
959 PM EDT Tue Jul 25 2017

.SYNOPSIS...
High pressure moving by to the north is expected to provide cooler
temperatures on Wednesday. Another front will move in from the
northwest late in the week, with cooler and drier conditions
arriving behind it for the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 10pm EDT Tuesday:  An area of thunderstorms has arisen along
the mountains and foothills of the NC/SC border area.  Sufficient
CAPE continues to exist to allow storms, though storm strenth has
been trending downward over the last 15 minutes.

The pattern of events on Wednesday may be fairly similar to today,
with some widely scattered afternoon showers, but low chances for
anything very strong.

Not much change in the synoptic setup over the last 12 hours as an
H5 trof ejects over the northeast CONUS, and a large anticyclone
dominates westward across the plains. At the surface, a
quasistationary frontal axis remains draped in the vicinity of the
I85 corridor.

Temperatures on Wednesday will be a bit cooler than today thanks to
the aforementioned mid/late morning stratus potential, yet should
still top out within 1-2 degrees of normal across the
piedmont/fthills, and at normal levels across the higher terrain.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 200 PM EDT Tuesday: Upper-level heights will begin falling
from the Great Lakes to the Ohio River Valley Wednesday night
through Thursday. At low levels, Light southerly upslope flow could
permit isolated to scattered showers, with a thunderstorm or two, to
persist into the nightttime hours early Thursday across the southern
mountains. Otherwise, anticipate slightly better diurnal convective
coverage across the NC mountains Thursday afternoon and evening
ahead of the approaching upper support as surface-based instability
increases a bit over previous days. Improving westerly steering flow
will also likely bring scattered convection farther east of the Blue
Ridge along the I-40 corrdor into the western NC foothills/piedmont
into Thursday evening. Surface to 6 km bulk shear magnitude may rise
to 25 to 30 kt across the northern tier by Thursday afternoon as
these westerlies improve. Thus, anticipate a gradual change in the
character of the convection to more multi-cell types by late
Thursday.

The upstream shortwave energy will cross the forecast area from the
northwest Thursday night through Friday ahead of much stronger
heights falls carving out a more prominent trough from the Great
Lakes to the Appalachians. The best moisture and forcing will occur
around the passing cold front, but the numerical models still
exhibit quite a bit of spread on the timing. The faster NAM/ECM
camps bring clouds and moisture into the region very early Friday
and thus limit instability, while the GFS timing is much later in
the day. Indeed, the slower GFS would keep precipitation going well
into Friday night across the southeast half of the area. This will
play havoc will instability around the fropa and also shear
profiles, but an uptick in storm organization is certainly possible
Friday afternoon and evening. For now, will blend the timing
slightly toward the faster solutions which is preferred given the
push from the rapidly falling upstream heights.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 200 PM EDT Tuesday: A trend toward drier and cooler conditions
seen in the previous forecast was continued with this forecast
package. By Saturday morning, a surface cold front should have moved
through our area and settled to our south. The GFS/ECMWF remain in
agreement on maintaining an amplified pattern and sweeping this
front through towards the Gulf coast, with an upper longwave trough
deepening over the eastern CONUS over the weekend and into early
next week. There is also better agreement in the global models with
respect to drier air arriving behind the front...and with basically
all convection remaining suppressed Saturday and Sunday over our
area in yet another guidance cycle, have lowered pops even more to
below climo over the weekend. The Bermuda high reasserts itself a
bit more over the southeast early next week, and gradual moistening
of the column will lead to pops returning closer to average by
Tuesday and Wednesday.

With the above-mentioned upper trough expected to deepen
dramatically over the eastern CONUS over the weekend and into early
next week, maintained the downward trend in temperatures through the
period. Large adjustments weren't made with this package, but
temperatures more than 5 degrees below climo and dew points in the
mid to low 60s could make for some...dare I say it...rather pleasant
conditions for late July.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere:  Relatively stable weather pattern will
continue through Wednesday with some widely scattered afternoon
convective showers and light to variable winds.  Some patchy fog and
possible low OVC in the morning could affect some sites, especial KAVL.
Probability of getting convection at any give site is low enough to
not be worth mention in the TAFS at this time.  Some fog and stratus
overnight are possible as boundary layer cools.  How much is
difficult to be precise about, but will be less likely at KCLT and
KGSP which have slightly lower forecast relative humidity levels.

Outlook: Scattered diurnal convection can be expected each day
thru Friday across the region. Then drier air will filter in from
the north behind a passing cold front this weekend. Chances for
morning fog and stratus will also be possible each day in the
mountain valleys.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High 100%     High  95%     Med   73%     High  97%
KGSP       High 100%     High  97%     High  88%     High 100%
KAVL       High  95%     Low   47%     High  91%     High 100%
KHKY       High 100%     Med   78%     High  86%     High  90%
KGMU       High 100%     High  97%     High  94%     High 100%
KAND       High 100%     High  83%     High  98%     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...Carroll
NEAR TERM...CDG/WJM
SHORT TERM...HG
LONG TERM...Carroll
AVIATION...WJM

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
245 PM EDT Tue Jul 25 2017

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-261845-
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-
245 PM EDT Tue Jul 25 2017

This Hazardous Weather Outlook is for northeast Georgia, the
foothills and piedmont of western North Carolina and Upstate South
Carolina.

.DAY ONE...This Afternoon and Tonight.

Isolated to scattered thunderstorms will develop around the region
late this afternoon into this evening. Cloud-to-ground lightning
will be the main threat from any storm that develops. Some of the
thunderstorms may also produce brief but strong wind gusts.

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

..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.
..Friday...No hazardous weather is expected at this time.
..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.

.SPOTTER INFORMATION STATEMENT...

None.

HG

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
857 PM EDT TUE JUL 25 2017

NCZ504-260145-
Greater Burke NC-
857 PM EDT TUE JUL 25 2017

...A STRONG THUNDERSTORM WILL IMPACT SOUTHERN BURKE COUNTY UNTIL 945
PM EDT...

At 857 PM EDT, Doppler radar was tracking a strong thunderstorm 4
miles southeast of Morganton, or near Drexel, moving southwest at 5
mph.

Locations to be impacted include...
Morganton, Valdese, Icard, Drexel, Connelly Springs, Rutherford
College, Glen Alpine, South Mountains State Park, Lake Rhodhiss and
Hildebran.

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

&&

LAT...LON 3581 8158 3578 8156 3578 8153 3573 8142
      3556 8157 3557 8160 3556 8164 3557 8167
      3558 8169 3558 8170 3561 8172 3560 8174
      3561 8176 3568 8186 3583 8163
TIME...MOT...LOC 0057Z 041DEG 6KT 3571 8162

TDP

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
1032 PM EDT TUE JUL 25 2017

SCZ001-004-260315-
Greater Oconee SC-Oconee Mountains SC-
1032 PM EDT TUE JUL 25 2017

...A CLUSTER OF THUNDERSTORMS WILL IMPACT CENTRAL OCONEE COUNTY UNTIL
1115 PM EDT...

At 1031 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 8 miles north of
Walhalla to 3 miles west of Seneca. These storms were nearly
stationary.

Locations to be impacted include...
Seneca, Walhalla, Westminster, Oconee State Park, Lake Keowee,
Mountain Rest and Oakway.

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

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Gusty winds can blow down trees that are dead, or that have weakened
root systems. Outdoor furniture and similar items can be tossed
around if not anchored. Seek shelter indoors.

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 3459 8317 3460 8317 3460 8316 3461 8318
      3484 8327 3485 8327 3485 8325 3488 8324
      3488 8321 3489 8320 3492 8316 3493 8316
      3493 8311 3495 8313 3497 8312 3495 8305
      3461 8290 3456 8312
TIME...MOT...LOC 0231Z 091DEG 3KT 3489 8311 3468 8302

TDP