Flash Flood Warning 19, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
444 PM EDT Sat Jun 8 2019

.SYNOPSIS...
A low pressure system west of the region will continue to pump
moisture from the Gulf of Mexico over the southern Appalachians and
surrounding areas today through Monday. A cold front will arrive
from the northwest on Monday night, but likely stall over the region
on Tuesday, with abundant moisture returning through Wednesday.
Another cold front will finally push through the region late in the
week to bring in drier air from the west.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 440 pm: The strongest thunderstorms with the heaviest
rainfall rates continued to be along to just ahead of a band of
convection that was across the I-26 corridor, slowly marching
towards the northeast. Rainfall rates upwards of four to five
inches per hour have been noted over the past couple of hours,
likely causing at least minor flooding and decent stream rises.
Fortunately, the heaviest rainfall rates have been on the move
so far (even if slowly), greatly reducing the threat for
significant flooding. Given the high risk for flooding with the
deep moisture and moderate forcing in place, will be on the
lookout for continued threats for flooding, especially with any
stalled or training storms. The current Flood Watch (see FFAGSP)
over most of the region looks well placed as rounds of heavy
rainfall continue through the near term. There may also be a few
stronger storms over the I-77 corridor through early this
evening with moderate instability and downdraft potential
(DCAPE) in place.

Otherwise, coverage of heavy showers and storms increasing along the
I-40 corridor in the foothills and Piedmont, deteriorated antecedent
conditions developing in response to widespread 2-4 inch amounts
(with locally higher amounts up to 7") that have occurred since
Thursday night has lowered FFG values to only 1-2" in an hour, and
those rates will probably become common from late afternoon into the
evening.

As we progress into the overnight, the situation is expected to only
become more dire, as the low level flow backs and intensifies,
strongly increasing the upslope component into the Blue Ridge during
the evening, lasting through at least Sunday morning. Widespread
rainfall amounts of 4 to 6 inches are expected along the Blue Ridge
from this afternoon through Sunday, likely resulting in fairly
widespread flash flooding, some of which will be significant.
Landslides may also become an increasing concern in the complex
terrain. Meanwhile, with convection gradually becoming more
concentrated near the Blue Ridge late tonight into tomorrow (before
coverage increases again Sunday afternoon), lesser amounts are
expected across the remainder of the forecast area, but additional
amounts of 2 to 4 inches, with locally higher amounts are expected
across the remainder of the Watch area through the day tomorrow.
This could result in significant flash flooding in areas that have
already seen very heavy to excessive rainfall since Friday, and in
urban and other flood prone areas over which cells are able to train.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 250 PM EDT Saturday: Deep southerly flow remains over the area
Sunday night as the upper trough axis remains just to our west. The
very high PW values, weakly unstable air mass, and very deep warm
cloud layers will combine to keep the heavy rain and flood threat in
place. The coverage tapers off late Sunday night as the low level
flow turns more southwesterly as the trough begins to move and a
cold front approaches from the west. The trough and front move into
the area Monday then east Monday night. This will bring widespread
convection back across the area as it lines up with peak heating.
Overall heavy rain threat looks lower as the flow is more
southwesterly and warm cloud processes diminish. However, with
increased convective potential, isolated heavy rain and flooding
could still develop. The next shift will probably need to extend the
flood watch to Sunday night and possibly Monday. However, the
extension into Monday could be held until later.

The guidance agrees that precip should taper off Monday night as
drier high pressure builds in behind the cold front. The NAM and the
GFS keep Tuesday dry which will be much needed by then. However,
the 12Z ECMWF has come in with a stalling cold front. It does dry
out the area north of I-85 but keeps precip along and to the south
of this corridor. For now, it does show the lingering precip to be
light. Have gone with a blend for PoP which brings chance PoP back
along the I-85 corridor during the day.

Warm and muggy Sunday night and Monday with some cooling and drying
dew points behind the front Monday night and Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 140 pm EDT Saturday: Starting at 00Z Wednesday with low
pressure over the Florida Panhandle and ready to move toward the
Carolinas Tuesday night into Wednesday. A trough is seen on the
500mb pattern Tuesday evening crossing the Plains States. The low
will spread rain northward over the Carolinas Wednesday morning and
then be picked up by the trough as the trough moves over western
portions of the Ohio Valley late Wednesday.  Instability should be
limited to areas east of the mountains, particularly along and east
of the I-77 corridor on Thursday as the low pulls NE.  Models show
CAPE values 200 to 700 over the NC piedmont on Thursday. Therefore,
some convection is expected on Thursday before the much drier air
wraps in from the SW with the trough and low moving NE and away from
our area by late Thursday.  Expect much drier air on Friday and
Saturday.

Dry high pressure will be in control of our weather Friday and
Saturday.  The next rain system will be approaching from the NW late
in the weekend but that is after the current forecast.

Max Temps are expected to be over 10 degrees below normal Wed, then
5 to 8 degrees below normal Thursday through Saturday. Min Temps
will be about 5 degrees below normal Tues night then 5 to 8 degrees
below into weekend.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Convection will continue to increase in
coverage and intensity throughout the afternoon, and a categorical
mention of TSRA is warranted at all terminals, as early as 18Z at
KAND, and as late as 22-24Z  at KHKY and KAVL. (All sites get a
tempo for at least a couple of hours before that.) Bursts of
torrential rainfall will be accompanied by IFR (or worse) visby, and
this is advertised at all sites except KHKY and KCLT, with those
sites getting MVFR visby only due to lingering timing uncertainty.
At least scattered convection will linger through the overnight
across the terminal forecast area, with more widespread activity
expected to eventually become concentrated near the Blue Ridge
toward daybreak. Otherwise, widespread IFR/LIFR cigs are expected to
begin redeveloping by around midnight and persist through the
morning, with only modest improvement expected during the latter
part of the period.

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

Confidence Table...

            20-02Z        02-08Z        08-14Z        14-18Z
KCLT       High 100%     Med   73%     Med   72%     High  81%
KGSP       High 100%     High  85%     Med   75%     High  87%
KAVL       High  83%     Med   76%     Med   78%     High  85%
KHKY       High  81%     Med   78%     Med   75%     High  96%
KGMU       High  94%     Med   62%     High  90%     Med   79%
KAND       High  98%     Med   72%     High  85%     High  80%

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

&&

.HYDROLOGY...
Updated Flash Flood Guidance values for 6-hour periods are generally
running 1 to 3 inches, with a few locations 4+ within the Flash
Flood Watch area. These rates will be locally attainable given the
rain  efficiency observed so far today well as the potential for
training rain bands in regions with deep (12+ kft) warm cloud
layers. The WPC Moderate risks of Excessive Rainfall for days 1 and
2 look very well placed.

Although antecedent conditions were quite dry leading up to this
event, flooding in urban areas developed very quickly yesterday as
local drainage systems were overwhelmed by the rainfall rates. This
will likely occur again this evening and again on Sunday within the
Watch area, while significant flash flooding of small streams is
possible this evening through Sunday, especially across the North
Carolina foothills and northern Piedmont.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Flash Flood Watch through Sunday evening for GAZ010-017-018-
     026-028-029.
NC...Flash Flood Watch through Sunday evening for NCZ033-035>037-
     049-050-053-056-057-059-062>065-068>072-082-501>510.
SC...Flash Flood Watch through Sunday evening for SCZ001>014-019.

&&

SYNOPSIS...DEO
NEAR TERM...JDL/RMM
SHORT TERM...RWH
LONG TERM...DEO
AVIATION...JDL
HYDROLOGY...JDL

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
402 PM EDT Sat Jun 8 2019

GAZ010-017-018-026-028-029-NCZ033-035>037-049-050-053-056-057-059-
062>065-068>072-082-501>510-SCZ001>014-019-092015-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Iredell-Davie-Yancey-Mitchell-Buncombe-Catawba-Rowan-
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-
402 PM EDT Sat Jun 8 2019

...FLASH FLOOD WATCH IN EFFECT THROUGH SUNDAY EVENING...

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

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.

In addition, some of the thunderstorms this evening will be strong
with very gusty winds and frequent lightning.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Flash Flood Watch.

.SPOTTER INFORMATION STATEMENT...

None.

NCZ048-051-052-058-092015-
Madison-Swain-Haywood-Graham-
402 PM EDT Sat Jun 8 2019

This Hazardous Weather Outlook is for western North Carolina.

.DAY ONE...Tonight.

Several rounds of heavy rain producing showers and thunderstorms
will affect the region tonight. Local 1 to 2 inch per hour rainfall
rates will be possible in the heaviest downpours, and localized
flooding could result.

In addition, some of the thunderstorms this evening will be strong
with very gusty winds and frequent lightning.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

The active, wet pattern will continue Sunday through mid-week.
Additional heavy rainfall and flooding will be possible each day.

.SPOTTER INFORMATION STATEMENT...

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

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