Flash Flood Warning 45, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
251 PM EDT Tue Aug 21 2018

.SYNOPSIS...
A cold front will move to the Carolina coast on Wednesday.
Expect cool high pressure to pass across the eastern states
Thursday and Friday then move offshore for the weekend. As the upper
trough moves out over the Atlantic this weekend, a hot ridge is
expected to replace it next week. So expect cooler than normal
weather to end this week then hot weather next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 245 PM EDT Tuesday: An upper closed low, which is expected to
gradually open as it progresses eastward tonight, continues to push
into the OH Valley this afternoon, as it's associated north to south
oriented cold front is currently positioned across central
Tennessee. Given latest guidance, anticipate the front to reach the
western extent of the FA tonight, pushing through the eastern fringe
by Wednesday morning.

For the rest of today, despite lingering cloud cover through much of
this morning which kept the area a bit more stable than previously
anticipated, scattered showers and thunderstorms are gradually
increasing in coverage as clouds begin to decrease in spots. With
some destabilization and the approaching front from the west
providing additional lift especially into this evening, latest CAM
guidance continues to suggest scattered showers and thunderstorms
through tonight. Weak shear could lead to a few broad rotating
storms, but overall anticipate primary threat to be damaging winds,
as the higher potential for widespread severe weather remains off to
the north. With PWATs nearing two inches, heavy downpours or
localized minor flooding will be possible. Low temperatures tonight
will drop into the upper 60s/low 70s, though cooler across the
mountains.

Overnight, isolated showers will be possible west of the I-77
corridor through into Wednesday morning, with patchy areas of fog
possible across the mountains as the cold front exits the FA off to
the southeast. Have kept low PoPs for isolated showers along the TN
border through Wednesday afternoon with NW flow, while elsewhere,
quiet conditions are expected as drier air infiltrates in. High
temperatures will be around normal.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 250 PM EDT Tuesday: Guidance in good agreement showing a break
in the active weather for at least a couple of days. Upper trough
axis moves east and ridging begins building in from the west. At the
surface, high pressure builds in from the west with deep layer
drying. No convection expected either day. Highs will be nearly
steady around 5 degrees below normal. Lows Thursday morning will be
around 5 degrees below normal but fall to nearly 10 degrees below
normal Friday morning. The cooler temps will also be accompanied by
very comfortable dew points falling into the 50s both days.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 155 PM EDT Tuesday: Starting 00Z Saturday. Cool surface high
pressure moves off the New England coast Friday night and Saturday
but still riding over the Carolinas ahead of a progressive Great
Lakes trough. The easterly flow ahead of the trough will help to
keep temperatures below normal for one last day on Saturday. The
trough moves east of New England on Sunday as a Texas centered 500mb
ridge builds east. This ridge will gradually establish itself over
the SE states through mid week becoming centered somewhere near our
area by Wednesday. This happens as a trough develops over the West
Coast. Some diurnally driven convection can be expected for our area
mainly for the mountains where differential heating will help create
updrafts leading to shower and storm development. Under the gradual
warming effect of the ridge, max temps will rise 2 to 3 degrees each
day in the medium range period. Min temps start just below normal
early Saturday then around or just above normal through first half
of the week.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: With an approaching cold front currently west
of the area, mainly MVFR prevails this afternoon as low cigs
continue to linger much longer than expected, though a few areas are
beginning to scatter out to VFR, while others have briefly
deteriorated to IFR given a SHRA/TSRA moving over the TAF site.
Expect showers and thunderstorms to increase in coverage this
afternoon and tonight as the cold front moves into the area,
bringing periods of IFR heavier downpours/lower cigs and gusts up to
30 kts possible in stronger storms. Per latest guidance, anticipate
coverage of SHRA/TSRA to become isolated in nature overnight,
diminishing with the cold front. Otherwise, SW winds AOB 12 kts will
prevail through the rest of today, gradually veering with the cold
front, beginning across the mountains later tonight, and eventually
at KCLT towards Wednesday morning. Isolated showers will be possible
across the mountains Wednesday morning, which could bring lingering
MVFR/IFR to KAVL. Otherwise, expect VFR.

Outlook: Quiet weather conditions will be in place behind the cold
front as drier air infiltrates in. Thus, expect VFR to prevail
through the end of the week.

Confidence Table...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       High 100%     High 100%     High  98%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  96%     Low   49%     High  84%
KHKY       High  98%     High 100%     High 100%     High 100%
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...DEO
NEAR TERM...SGL
SHORT TERM...RWH
LONG TERM...DEO
AVIATION...SGL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
618 AM EDT Tue Aug 21 2018

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-221030-
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-
618 AM EDT Tue Aug 21 2018

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

.DAY ONE...Today and tonight.

A robust cold front will approach the forecast area from the west
and help to generate numerous showers and thunderstorms. Some of
these storms could become severe and produce large hail and damaging
wind gusts. Isolated urban and small stream flooding is also a threat
with these storms. The flooding threat will be greatest over the
higher terrain.

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

No hazardous weather is expected.

.SPOTTER INFORMATION STATEMENT...

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

JPT