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435
FXUS62 KCAE 240741
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
341 AM EDT Tue Sep 24 2024

.SYNOPSIS...
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High pressure over the SE US will keep warm conditions over the
Southeast through mid week. Multiple shortwaves crossing the
region will bring chances for precipitation through midweek.
Confidence is increasing that impacts due to the tropical system
in the Gulf will be felt in the forecast area Thursday into
Friday, but uncertainty remains in the exact track and impacts
of the system.
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&&

.NEAR TERM /TODAY AND TONIGHT/...
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Key Message(s):

- Upper ridge begins to weaken but still very warm
- Marginal risk of severe storms north of Columbia and scattered
afternoon convection

Current satellite imagery shows widespread stratus developing
across the northern Midlands with some mid level clouds across
the remainder of the area. Air mass remains mild with abundant
low level moisture in place with dewpoints in the upper 60s to
lower 70s.

The upper ridge axis shifts east of the forecast area today
with slightly falling 500mb heights and increasing mid level
flow this afternoon and evening. Hi-res guidance differs in
timing and location of convection today but all consistently
showing at least isolated to scattered convection. There appears
to be some weak convergence and possible weak shortwave energy
traversing the area mid morning which may support isolated
showers across the eastern Midlands. As the atmosphere
destabilizes this afternoon with MLCAPE values at or above 1000
J/kg and low level convergence with some weak large scale ascent
moving over the region, expect scattered convection focused
more across the western Midlands into the northern Midlands by
late afternoon into the early evening hours. The increased mid
level flow should be sufficient enough to support isolated
severe thunderstorm threat given plenty of moisture in place
with PWATs around 1.8 inches. SPC has the northern Midlands
outlooked in a marginal risk for severe weather. Temperatures
should continue to be warm and above normal with highs ranging
from the mid 80s north to lower 90s south.

Tonight, lingering showers are possible across the northern
Midlands in an area of low level convergence and deeper moisture
but isentropic lift shifts northward through the night and pops
should decrease through morning. Overnight lows should be
limited by clouds and very moist air mass with lows expected to
be in the upper 60s to around 70 degrees.
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&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
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Key Message(s):

- Above average temperatures continue.
- Chances for precipitation in the afternoon and overnight hours.

Wednesday is shaping up to be relatively quiet ahead of the impacts
associated with Potential Tropical Cyclone (PTC) 9. Upper ridging
over the area is forecast to drift further east through the day and
overnight. Meanwhile, an upper trough is expected to transition to
an upper cut-off low over the lower Mississippi Valley, which is
anticipated to play a key role on the track of PTC 9 going forward.
A frontal boundary associated with the transitioning trough is
forecast to edge eastward, but then stall out as the trough closes
off. Precipitation associated with this feature is forecast to
spread into South Carolina/Georgia from the west, bringing chances
for rain to the western portions of the forecast area.

Meanwhile, PTC 9 is forecast to travel northward into the
northeastern portions of the Gulf and intensify into
potentially a major hurricane. Current forecast is that it won`t
make landfall during this period. However, precipitation
associated with PTC 9 could be reaching the CSRA late Wednesday
night.

Temperatures are still expected to be on the warm side on Wednesday,
but a few degrees cooler than Tuesday. Overnight lows remain mild,
around 70.
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&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
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Key Message(s):

- Tropical system continues to develop in the Gulf, but uncertainty
  remains in its track.
- Impacts from the tropical system anticipated for Thursday and
  Friday.

Latest guidance shows that Potential Tropical Cyclone (PTC) 9 is
forecast to make landfall sometime Thursday as a hurricane around
the big bend of Florida, then continue tracking northward. However,
there is uncertainty in the strength and track of the system as it
comes onshore and moves north. It does appear that PTC 9 will be a
faster moving system, but models disagree on just how fast it will
move. Impacts from PTC 9 are expected to begin affecting the area
through the day Thursday and continue into Friday. The potential
impacts for our area include areas of heavy rain that could lead to
flash and/or river flooding, winds gusting to 35 mph (particularly
in the CSRA where chances are in the 40-50% range), and tornadoes
due to the forecast track of the system. The level of these impacts
are dependent on the exact track of PTC 9 as it moves inland.

PTC 9 is anticipated to be absorbed into the upper low that is
meandering around the mid to lower Mississippi Valley. As it does,
chances for showers of varying degree continue into next weekend
before the upper feature is able to move completely out of the
area.
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&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
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Generally expecting VFR conditions through the TAF forecast
period with the exception of possible MVFR cigs in stratus this
morning at CAE/CUB.

Similar to last night, low clouds have formed across NC and
into the northern Midlands while some mid level clouds continue
to form over the southern Midlands and CSRA. Expect these lower
clouds to build southward a bit more toward the CAE/CUB
terminals but confidence is limited as to whether or not it will
make it so have MVFR cig restrictions in a tempo group from
10-14z. Also included a tempo group at OGB for possible brief
stratus conditions there. Further south at AGS/DNL fog seems to
be more likely if anything occurs but mid level clouds are a
deterrent at this time.

VFR conditions expected all terminals by 15z and with abundant
low level moisture in place and weakening upper ridge expect
scattered diurnal convection to develop but timing and coverage
is too uncertain at this time to include in the forecast. Winds
should pick up from the south to southwest around 5 to 7 knots
by late morning through the afternoon before diminishing again
with sunset.

EXTENDED AVIATION OUTLOOK...Some restrictions in stratus
possible Wednesday morning then restrictions along with strong
winds becoming possible Thursday through Saturday associated
with a potential tropical system moving west of the forecast
area.
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&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...None.
GA...None.

&&

$$