Flash Flooding and Flooding in North Carolina, May 19, 2020

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
147 PM EDT Tue May 19 2020

.SYNOPSIS...
A large upper low will linger over the Tennessee Valley Region
through mid week as it slowly weakens. This weather pattern will
generate multiple rounds of moderate to heavy rain across much of
our region that continues into the latter half of the week. More
typical late spring weather is expected to return over the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 145 PM EDT Tuesday: Main update for the 18Z TAF issuance along
with minor adjustments made to temperatures to coincide with latest
trends as the rest of the near term forecast remains on track.
Latest radar imagery continues to depict showers, along with a few
thunderstorms now as well, moving northward across the area as
previously anticipated. Current temperatures range from the mid to
upper 60s.

A Flash Flood Watch remains in effect for portions of the area.
Please see latest Public Information Statement regarding the
increasing threat for landslides and debris flows across the
mountains and foothills over the next few days.

Previous discussion: The large h5 low will continue to gradually
drift south today and tonight as it maintains a nearly symmetrical
appearance.  By the end of the near-term period it will be centered
just to our west and over Eastern TN/Northern GA. At the sfc, the
main low will not move much today/tonight with the heavier precip
bands expected to shift more to the northern part of the CWFA, say
in the vicinity of the I-40 corridor, as the low-lvl flow becomes
more NELY later this aftn. The resulting hybrid wedge-like
configuration will persist well into Wednesday with the north to
south temperature gradient strengthening each day. As for the
thunderstorm potential today and tonight, model profiles generate
less instability compared to yesterday with weaker lapse rates from
the warmer air aloft. Therefore, it's pretty unlikely that any
thunderstorms will reach severe criteria.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 323 am EDT Tuesday: We will remain under the influence of a
strong upper low through the middle part of the week. The latest
guidance has the center of this feature a little bit farther south
on Wednesday, which brings more of a focus for heavy precip maybe
a bit farther down the Escarpment toward northeast GA. The precip
amounts down the chain are not appreciably higher yet, so the
southwest extent of the watch still looks well-placed. Meanwhile,
as the low makes its closest wobble to the srn Appalachians, the
main plume of moisture should translate slowly eastward across
the fcst area during the day and into Wednesday evening. The low
level convergence will orient itself in a SE to NW fashion, pointed
right at the NC mountains during this period, with an anomalously
strong easterly flow transporting copious moisture up into northwest
NC. This time period will be of great concern for ongoing flooding
across the NC mtns and foothills, with areas outside the mtns and
particularly the Charlotte metro area having perhaps their highest
threat for new flooding. Think it wise to expand the Watch now
to cover the remainder of the Charlotte metro area. Over the mtns
and near the Escarpment, our risk for landslides and debris flows
may also maximize Wednesday and Wednesday evening. Temperatures
through this period will remain well below normal because of the
heavy rain and extensive cloudiness. The conveyor belt of moisture
should get slowly pushed off to the northeast Wednesday night
and Thursday morning and some drier air should wrap in across
northeast Georgia as well. Thus, our precip probs should start
to tail off on Thursday, although they remain high across the NC
part until Thursday night. The new ECMWF is a bit more optimistic
with a quicker timing of moving drier air into the region, so a
downward trend on the precip chances was employed. Temps should
rebound on Thursday as well.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 210 AM EDT Tuesday: Model discrepancies remain as to the
eventual demise or departure of the upper low on Friday, with the
GFS still lifting it out over the OH Valley on a northeast track by
sunrise, but the ECMWF taking a slower eastern track and keeping it
close enough to our north to keep us under a stronger cyclonic flow
aloft. Either way, forcing and moisture should be on the downswing
on Friday, but with enough left over for diurnally enhanced precip
probabilities that favor the mtns. Even in the wake of the low,
model differences abound, and thus confidence suffers. Some kind of
upper ridging is expected to take hold over the weekend, but will
it be more amplified like the ECMWF or flatter like the GFS. The
former favors a purely diurnal precip scenario no better than a
summertime 30 mtns/20 Piedmont percentage, but the latter would
see a steady train of weak upper waves moving thru the flat ridge
to keep precip chances fluctuating but not completely going away
at night over the mtns. Both scenarios favor above normal temps
and a relatively humid air mass. The fcst will keep a diurnally
modulated precip forecast until a clearer signal is seen.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
At KCLT and Elsewhere: A mixture of VFR/MVFR/IFR/LIFR prevails
across the area this afternoon with ongoing scattered showers and
lowered cigs. Intermittent periods of improving flight restrictions
will be possible through this evening per latest satellite trends.
Expect increasing potential for VCTS/-TSRA this afternoon embedded
with heavy rain showers. Expect deteriorating flight restrictions
tonight and into Wednesday with low cigs, patchy fog, and showers.
East-northeasterly winds, gusty at times, will prevail at the NC TAF
sites, with the southeasterly winds at the SC sites gradually
becoming east-northeasterly later this afternoon into this evening.

Outlook: Showers and thunderstorms will continue into Wednesday and
possibly Thursday, creating flight restrictions. Expect a gradual
drying trend towards the end of the week.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High  85%     Med   75%     High  94%
KGSP       High 100%     Low   35%     High  90%     Med   69%
KAVL       High  81%     Low   55%     High  90%     Med   69%
KHKY       High 100%     High  95%     High 100%     High  94%
KGMU       Med   75%     Med   60%     Med   65%     Med   75%
KAND       High  87%     High  95%     Med   65%     Med   64%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Flash Flood Watch through Thursday morning for NCZ033-035>037-
     049-050-053-056-057-064-065-068>072-082-501>510.
SC...Flash Flood Watch through Thursday morning for SCZ002-003-
     005>010-013-014.

&&

SYNOPSIS...JPT
NEAR TERM...JPT/12
SHORT TERM...PM
LONG TERM...PM
AVIATION...12

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
1004 AM EDT Tue May 19 2020

NCZ033-035>037-049-050-053-056-057-064-065-068>072-082-501>510-
SCZ002-003-005>010-013-014-201415-
Avery-Alexander-Iredell-Davie-Yancey-Mitchell-Buncombe-Catawba-Rowan-
Transylvania-Henderson-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-
Union NC-Caldwell Mountains-Greater Caldwell-Burke Mountains-
Greater Burke-McDowell Mountains-Eastern McDowell-
Rutherford Mountains-Greater Rutherford-Polk Mountains-Eastern Polk-
Pickens Mountains-Greenville Mountains-Greater Pickens-
Greater Greenville-Spartanburg-Cherokee-York-Anderson-Union SC-
Chester-
1004 AM EDT Tue May 19 2020

...FLASH FLOOD WATCH IN EFFECT THROUGH THURSDAY MORNING...

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

.DAY ONE...Today and 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 to the heavy rainfall threat, scattered thunderstorms
are likely again today and tonight. The main threats from these
thunderstorms will be brief, gusty winds and dangerous cloud to
ground lightning.

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

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...

Spotter activation may be needed. Please relay any information about
observed severe weather to the NWS while following all local, state,
and CDC guidelines.

GAZ010-017-018-026-028-029-NCZ048-051-052-058-059-062-063-SCZ001-004-
011-012-019-201415-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Madison-Swain-Haywood-
Graham-Northern Jackson-Macon-Southern Jackson-Oconee Mountains-
Greater Oconee-Abbeville-Laurens-Greenwood-
1004 AM EDT Tue May 19 2020

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

.DAY ONE...Today and tonight.

There is the increasing likelihood of excessive rainfall today and
tonight, as periodic waves of showers and thunderstorms are expected
to move across the region. Across the mountains, the threat for
landslide activity will also increase. In addition to the heavy
rainfall threat, scattered thunderstorms are likely again today and
tonight. The main threats from these thunderstorms will be brief,
gusty winds and dangerous cloud to ground lightning.

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

Substantial rainfall is expected again on Wednesday and early Thursday,
as periodic waves of showers and thunderstorms move across the region.
The threat for flooding will remain elevated through Thursday. Across
the mountains, the threat for landslide activity may also increase
through Wednesday. Eventually, the flood threat along main stem
rivers will also increase and remain elevated through Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed. Please relay any information about
observed severe weather to the NWS while following all local, state,
and CDC guidelines.

JPT/12

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1256 PM EDT TUE MAY 19 2020

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1240 PM     FLOOD            4 SSW OLD FORT          35.58N 82.20W
05/19/2020                   MCDOWELL           NC   EMERGENCY MNGR

            LITTLE CROOKED CREEK OVERFLOWING ONTO ROY MOORE RD.

&&

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