149
FXUS62 KGSP 170259
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1059 PM EDT Mon Sep 16 2024

.SYNOPSIS...
A semi tropical low will move inland over the Carolinas
tonight and Tuesday bringing heavy rain and gusty winds. The low
will weaken through mid week with less wind and rain. By Wednesday,
the remnant low will stall out over the Mid-Atlantic, while high
pressure begins to build into the region from the north and west
late in the week.

&&

.NEAR TERM /THROUGH TUESDAY NIGHT/...
Key Messages:

1) Potential Tropical Cyclone 8 Will Bring Heavy Rain and Gusty
Winds to the Western Carolinas

2) A Flood Watch for Flash Flooding is in Effect for the Charlotte
Metro Area through Tuesday Morning

3) A Wind Advisory is in Effect for Locations Along I-77 through
Late Tonight

As of 10:35 PM EDT Monday: Potential Tropical Cyclone (PTC) 8
continues to gradually make its way inland over the Carolinas
late tonight. A Wind Advisory remains in effect through 2am EDT
for most locations along I-77 as high-res models show wind gusts
reaching 40+ mph over these areas. Gusts could be strong enough
to knock down a few trees, which may result in isolated power
outages. This system will continue to track WNW and further in-
land overnight and Tuesday morning. This will allow both cloud
cover and precip to gradually expand westward thru early Tuesday.
The system is still expected to stall over the Western Carolinas
on Tuesday, allowing cloud cover and rain chances to linger thru
the end of the near-term period late Tuesday. Expect storm total
precip amounts to be the lowest (generally less than an inch)
across northeast GA, the southwest NC mtns, and the western SC
Upstate based on the latest track for PTC 8. Higher precip amounts
(1 to 3 inches) are expected across the eastern SC Upstate, NC
Piedmont, and the northern and central NC mtns. The highest amounts
(3 to 5 inches) are most likely along the Blue Ridge Escarpment and
higher elevations of the NC mtns, although locally higher amounts
cannot be ruled out over these locations owing to enhanced upslope
flow. As such, a Flood Watch for Flash Flooding remains in effect
for the Charlotte Metro area thru early Tuesday morning as this
area has wetter antecedent conditions from recent rainfall. Winds
should weaken later Tuesday morning as the pressure gradient ass-
ociated with PTC 8 weakens and the system becomes less organized.
Clouds will remain bkn to ovc thru the day, helping keep tempera-
tures well-below climatology on Tuesday.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
As of 208 PM Monday: By tomorrow night, the remnants of a weak
tropical cyclone are forecast to be centered over the forecast area,
but a surface reflection will be hard to come by. The remnants will
instead manifest as a weak closed upper low that will slowly fill
through the day on Wednesday before opening into a shortwave trough
and lifting into New England on Thursday. A broad area of showers
will likely be ongoing tomorrow night, especially across the western
foothills and mountains, with at least scattered showers expected to
linger through the rest of the night across much of the area. The
presence of the upper low in concert with 1.5-1.75" PWATs will
promote above normal coverage of showers on Wednesday with
temperatures several degrees below average. Rain chances will begin
to decrease on Thursday as the evolving upper trough lifts away from
the area, but at least isolated to scattered showers look like a
good bet across much of the area.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 228 PM Monday: The large scale pattern finally becomes more
progressive by Friday into the weekend as persistent
blocking/troughing over the eastern CONUS breaks down. A tall upper
ridge that has been parked over the Great Plains will shift east
with heights rising across the Southern Appalachians as the ridge
axis nudges into the Tennessee Valley. At the same time, a sprawling
surface high will become centered over the Hudson Bay with high
pressure oozing down the spine of the Appalachians. This will send a
backdoor front through the area on Friday that will quickly scour
out low-level moisture with both PWATs and dewpoints falling.
Resulting intrusion of dry will bring an end to any lingering
showers with dry and pleasant weather through the weekend. Deep and
efficient mixing of the dry airmass will promote healthy diurnal
temperature swings of 20-25 degrees as morning lows in the upper 50s
to low 60s rebound into the upper 70s to low 80s during the day.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: What`s left of PTC 8 will gradually push
farther inland across the Carolinas tonight before stalling over
the fcst area on Tuesday. Widespread rain from this system will
continue to expand westward tonight and overnight, while precip
intensity gradually increases. Have prevailing RA/+RA for all
terminals by late tonight as the system is expected to stall over
our area. The precip shield should allow visby to range from IFR
to MVFR levels, although the heaviest bands of rain may allow cigs
to drop to LIFR levels at times. BKN to OVC cigs should also expand
westward thru late tonight with values gradually lowering thru the
overnight hrs with IFR to LIFR restrictions expected for most sites.
KAND, however, will likely remain MVFR. Gusty winds will continue
into the overnight before tapering off around daybreak Tues. Low-
level wind shear may also be an issue, mainly late tonight and into
the overnight. Still expect cig restrictions to linger thru much of
Tues, although visby should return to VFR by the afternoon, outside
of any lingering showers. I kept PROB30s and/or VCSH for any linger-
ing showers tomorrow aftn/evening. Wind direction will generally be
N to NE east of the mtns thru early Tuesday morning. Winds at KAVL
should gradually toggle more N/NW tonight and into Tuesday and then
back to NLY by Tuesday afternoon. Winds at KCLT and KHKY should gra-
dually turn more E/ESE Tuesday morning into Tuesday afternoon while
the Upstate sites will see winds favoring a NLY direction thru the
period.

Outlook: A weak upper low will linger over the Carolinas into Wed-
nesday before gradually weakening and lifting NE late Wednesday into
Thursday. This will keep precip chances and possible restrictions
around thru Thursday. On Friday, sfc high pressure builds into the
area from the north allowing drier weather and VFR conditions to
return.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Wind Advisory until 2 AM EDT Tuesday for NCZ057-070>072-082.
     Flood Watch until 8 AM EDT Tuesday for NCZ057-070>072-082.
SC...Wind Advisory until 2 AM EDT Tuesday for SCZ009-014.
     Flood Watch until 8 AM EDT Tuesday for SCZ009.

&&

$$

SYNOPSIS...DEO
NEAR TERM...JPT
SHORT TERM...TW
LONG TERM...TW
AVIATION...JPT