Flash Flood Warning 14, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
804 PM EDT Fri Jun 7 2019

.SYNOPSIS...
An active and wet weather pattern will be in place through the
middle of next week. A very slow-moving low pressure system will
approach the area from the west through the weekend. A cold front
will finally push through on Wednesday, bringing in some drier air
from the west.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 752 pm: Numerous showers and thunderstorms continue to
develop and move northeast across the wrn Carolinas early this
evening. Radar shows a back edge to this activity moving into
northeast Georgia as of 2330Z, so there could be something of a
lull in activity that would move in from the southwest later this
evening. In the mean time, we will adjust precip chances across
the fcst area to account for this. Severe weather is becoming less
of a concern as the ongoing convection uses up the 1000-1500 J/kg
of sbCAPE across the Upstate and northeast GA, but heavy rain is
becoming more of a threat. Will be monitoring how the convection
moving northeast across the Upstate interacts with the nascent cold
air damming wedge across the NC foothills and nw Piedmont regions
later this evening, with an eye toward the increasing potential
for flash flooding. Temps will be adjusted accordingly.

Although overall coverage of convection is expected to diminish to
scattered or even isolated overnight in most areas, as this boundary
becomes better-defined, it is expected to act as the primary focus
for showers/possible storms overnight, mainly in the vicinity of
the I-40 corridor. Mean W/SW cloud-bearing winds will be oriented
more or less parallel to this boundary, indicating the potential
for training cells and localized flash flooding.

The surface/in-situ cold air damming boundary will continue to
gradually intensify on Sunday, and this feature along with terrain
effects will be the primary impetus for focusing convection
and heavy rainfall on Saturday. The eventual location of this
boundary provides the main source of forecast uncertainty,
especially regarding qpf, as guidance remains quite variable
with its placement of the boundary during the day tomorrow. The
current forecast is for widespread 1-1.5 inch amounts across the
entire area during the day tomorrow, but focusing/potential for
training of convection along the boundary will certainly result in
locally higher amounts of 2-3 times that. As such, the threat for
localized flash flooding will increase throughout the afternoon
into the early evening hours.  Meanwhile, increasing southeast
upslope flow into the Blue Ridge escarpment will provide another
source of enhanced/focused lift that will likely result in locally
higher amounts much higher than the forecast basin-average qpf.

In terms of Flash/Flood Watch considerations, owing to the very
dry antecedent conditions, the fact that heavy rain has thus far
fallen outside of our particularly flood-prone areas (and outside
the Day 2 WPC Excessive Rainfall moderate risk), and the inherent
forecast uncertainty, we opted to wait one more forecast cycle
before zeroing in on a Watch area. "Watch fatigue" also has to be
a consideration, as once it's issued, it will undoubtedly be in
effect for several days.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH TUESDAY/...
As of 305 PM EDT Friday: The worst widespread conditions may develop
at the start of the short term period Saturday night as widespread
showers and thunderstorms with very heavy rainfall pile on top of
the heavy rainfall that will have fallen in the near term. Another 1
to 2 inches, up to 3 in the favored upslope areas, may fall. This
would likely push many locations over the brink in terms of flooding.

Of course, there is still some uncertainty with this scenario as a
wedge boundary will set up somewhere over or just south of our area.
If the boundary is farther south, convection along the boundary
could disrupt the low level moisture flux into the area, keeping the
heaviest rainfall along the boundary. The GFS favors this scenario
while the NAM and ECMWF favor a farther north solution. Otherwise,
there is good agreement on a 2 standard deviation above normal
moist air mass over the area, along with weak instability and
strong southerly low level jet and moderate upper level jet. These
features, of course, favor heavy rainfall. Agree on waiting for
another model run to issue any watches as hopefully the models and
us will have a better handle on antecedent conditions and location
of the heaviest rainfall.

There is also good agreement on the location of heavy rainfall
retreating to near the Blue Ridge Sunday and Sunday night. There
will still be widespread showers and storms over the area in the
moist, weakly unstable, and forced air mass. The flood potential may
continue, however, so watches may need to be extended across
portions of the area.

A cold front moves in from the west Monday. Again, although
widespread precipitation will continue, rainfall rates should be
diminishing greatly as the low level flow turns more southwesterly.
The front crosses the area Monday night and is to our south by
Tuesday taking the widespread precipitation with it. Although likely
PoP will be maintained, especially across the southern CWFA.

Highs will be below normal and lows will be above normal.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
As of 205 PM EDT Friday: Starting at 00Z Wednesday with the 500mb
pattern a rather tall rude over the West Coast and a broad trough
from the Rockies eastward.  A surface cold front will be moving off
the East Coast a wave of low pressure moves NE from northern
Florida Tuesday night into Wednesday.  There will be a strong wave
on the 500mb pattern crossing Iowa on Wednesday while closing off as
a low into Thursday. This low will open up again as a wave by late
Thursday as it crosses the Ohio Valley then moves faster into
eastern Canada Friday into Saturday.  Much drier air along with
surface high pressure should give us no POPs Friday into Saturday.

As the low pressure moves NE from the FL Panhandle Tuesday night
into Wednesday, the highest precipitable water values of 2 inches
and greater should be confined to areas east of I-85.  CAPE values
rather low with the highest on the GFS Thursday afternoon near 1000
south of CLT.

Max Temps around 10 degrees below normal Wed, 5 to 8 degrees below
Thursday and 3 to 5 degrees below normal on Friday.  Min Temps near
normal.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: A mixed bag of flight categories across
the region at the start of the period, with many locations VFR
away from ongoing thunderstorms, while IFR/MVFR was occurring
in conjunction with the convection. Complicating the issue was a
back door cold front/wedge boundary slowly moving southward over
the wrn Carolinas. Will include the restrictions in a TEMPO group
for the start of the TAF and then slowly pull back as this batch
of precip lifts northeast across the region in the early morning
hours. IFR ceilings/MVFR visibilities look like a good bet for the
pre-dawn hours and lasting into morning operations on Saturday,
with ceiling and visibility highly variable. Wind direction at KCLT
is problematic with an easterly component. Think it should stay
ESE through the evening hours, but expect this to come around to
ENE by morning operations. On Saturday, conditions still look grim
and variable as we have copious moisture available and periodic
bits of mid/upper forcing that could touch off a shower or storm
at any time. Not really a good time to focus on, so most TAF sites
get a broad brush, mainly MVFR for the balance of the day. Wind
should be mainly northeasterly.

Outlook: Deep moisture will persist across the region through
the weekend and into the early part of next week, with widespread
showers and thunderstorms, some with very heavy rain, and associated
restrictions. Long periods of MVFR to IFR are likely.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       Med   77%     Med   74%     Med   72%     High  84%
KGSP       High  84%     Med   70%     High  82%     Med   75%
KAVL       Med   79%     Med   79%     High  80%     High  85%
KHKY       High  85%     Med   71%     Med   78%     Med   71%
KGMU       High  88%     Med   71%     High  80%     Med   74%
KAND       High  98%     Med   72%     Med   75%     Med   65%

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...RWH
NEAR TERM...JDL/PM
SHORT TERM...RWH
LONG TERM...DEO
AVIATION...PM

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Special Weather Statement
National Weather Service Greenville-Spartanburg SC
553 PM EDT Fri Jun 7 2019

GAZ028-SCZ010-072230-
Hart GA-Anderson SC-
553 PM EDT Fri Jun 7 2019

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
NORTHEASTERN HART AND SOUTHWESTERN ANDERSON COUNTIES UNTIL 630 PM
EDT...

At 552 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 7 miles east of Hartwell, or 6 miles west of Starr,
moving northeast at 10 mph.

Locations to be impacted include...
Homeland Park, Starr, Anderson Airport, Lake Hartwell, Reed Creek and
Sadlers Creek State Park.

In addition to intense lightning, wind gusts up to 50 mph and half
inch 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.

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3434 8274 3433 8281 3443 8290 3455 8274
      3440 8258
TIME...MOT...LOC 2152Z 237DEG 10KT 3439 8280

RM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
623 PM EDT Fri Jun 7 2019

SCZ013-014-072330-
Union SC-Chester SC-
623 PM EDT Fri Jun 7 2019

...A STRONG THUNDERSTORM WITH INTENSE LIGHTNING WILL IMPACT
SOUTHWESTERN CHESTER AND SOUTHEASTERN UNION COUNTIES UNTIL 730 PM
EDT...

At 623 PM EDT, Doppler radar was tracking a strong thunderstorm with
intense lightning 16 miles southeast of Union, or 4 miles south of
Carlisle, moving east at 15 mph.

Locations to be impacted include...
Carlisle, Chester State Park, Tuckertown and Leeds.

In addition to intense lightning, wind gusts up to 40 mph and pea
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.

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 3445 8155 3446 8155 3460 8157 3468 8122
      3456 8122 3457 8142 3453 8143 3450 8142
      3449 8143 3450 8144 3449 8144 3449 8148
      3445 8153
TIME...MOT...LOC 2223Z 265DEG 17KT 3453 8147

RM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
633 PM EDT Fri Jun 7 2019

SCZ010-011-072315-
Anderson SC-Abbeville SC-
633 PM EDT Fri Jun 7 2019

...A CLUSTER OF THUNDERSTORMS WITH INTENSE LIGHTNING WILL IMPACT
SOUTHEASTERN ANDERSON AND ABBEVILLE COUNTIES UNTIL 715 PM EDT...

At 633 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms with intense lightning along a line extending from
12 miles south of Anderson to 15 miles southwest of Abbeville, and
moving east at 30 mph.

Locations to be impacted include...
Abbeville, Belton, Honea Path, Calhoun Falls, Due West, Iva, Lake
Secession, Donalds, Starr and Lowndesville.

In addition to intense lightning, 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...

Frequent lightning is occurring with these storms. 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 storms approach.

&&

LAT...LON 3407 8264 3409 8264 3413 8267 3414 8271
      3436 8278 3458 8243 3438 8229 3434 8233
      3432 8231 3428 8231 3422 8225 3416 8224
      3411 8226 3406 8233 3406 8244 3408 8248
      3407 8253 3402 8259
TIME...MOT...LOC 2233Z 261DEG 25KT 3434 8261 3402 8256

CSH

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
715 PM EDT Fri Jun 7 2019

SCZ011-019-080000-
Abbeville SC-Greenwood SC-
715 PM EDT Fri Jun 7 2019

...A CLUSTER OF STRONG THUNDERSTORMS WILL IMPACT NORTHEASTERN
ABBEVILLE AND GREENWOOD COUNTIES UNTIL 800 PM EDT...

At 714 PM EDT, Doppler radar indicated the leading edge of a cluster
of thunderstorms along a line extending from 11 miles southeast of
Anderson to 8 miles north of Abbeville to 9 miles southwest of
Greenwood, and moving east at 30 mph.

Locations to be impacted include...
Greenwood, Ware Shoals, Ninety Six, Due West, Donalds, Cokesbury,
Hodges, Lake Greenwood State Park, Greenwood State Park and Ninety
Six Historic Site.

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

LAT...LON 3402 8224 3400 8226 3429 8241 3437 8249
      3448 8232 3440 8224 3437 8218 3433 8217
      3431 8212 3430 8208 3424 8201 3424 8198
      3419 8192 3416 8191 3413 8188 3400 8223
TIME...MOT...LOC 2314Z 264DEG 24KT 3443 8247 3430 8234 3407 8222

CSH

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
819 PM EDT Fri Jun 7 2019

SCZ002-005-080100-
Pickens Mountains SC-Greater Pickens SC-
819 PM EDT Fri Jun 7 2019

...A STRONG THUNDERSTORM WILL IMPACT NORTHEASTERN PICKENS COUNTY
UNTIL 900 PM EDT...

At 819 PM EDT, Doppler radar was tracking a strong thunderstorm near
Pickens, moving northeast at 10 mph.

Locations to be impacted include...
Pickens, Dacusville and Pumpkintown.

Wind gusts up to 50 mph and half inch hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio and tv
stations, as well as local cable tv outlets for additional
information and possible warnings from the National Weather Service.

&&

LAT...LON 3494 8276 3506 8262 3503 8259 3502 8259
      3501 8260 3501 8257 3496 8253 3494 8252
      3486 8271
TIME...MOT...LOC 0019Z 237DEG 10KT 3490 8269

RM