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054
FXUS62 KCAE 182357
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
757 PM EDT Wed Sep 18 2024

.SYNOPSIS...
An upper low over the area will move slowly east to the coast by
early Thursday. A few showers or thunderstorms are possible
Thursday mainly in the east Midlands closer to the upper low.
Moisture is expected to decrease Friday. High pressure will
build into the area from New England over the weekend into early
next week with dry and seasonable temperatures expected.

&&

.NEAR TERM /THROUGH 7 AM/...

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Key Message(s):

- Lingering scattered showers this evening

An upper level low over upstate South Carolina has been moving
slower than rush hour traffic the last couple of days, but
finally shows some signs of at least drifting eastward this
evening on the water vapor loop. Still, spokes of vorticity
continue to rotate cyclonically around the upper low, and with
precipitable water values in the 1.6 to 1.7 inch range, there is
plenty of moisture around to allow for some scattered showers
for a few more hours. Where it doesn`t rain, skies will still
be mostly cloudy overnight.

Late tonight after midnight, I do think we will see some patchy
fog. We will have an extended period of very light to calm
winds tonight, and we could start to get some subsidence as the
final upper level vort pushes slowly eastward, setting up a nice
inversion.
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&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...

Key Message(s):

- Isolated to scattered showers Thursday mainly in the east
  Midlands, drier Friday.
- Seasonable temperatures.

Thursday and Thursday night...Upper low will move into eastern
North Carolina Thursday with long wave trough axis along the
coast moving east in the morning. Moisture remains relatively
high in the east Midlands with precipitable water near 1.75
inches. Models show a short wave trough moving through the area
in the afternoon with the strongest lift focused closer to the
Coastal Plain. Expect stronger diabatic heating than today
across the region. Latest model forecast soundings for Thursday
afternoon suggests moderate instability in the east Midlands
with surface based CAPE around 1000-1500 J/kg. Weaker
instability to the west due to lower moisture. Mid level
subsidence inversion stronger in the west. So, a few light
showers in the morning, then widely scattered/scattered showers
mainly in the eastern area during the afternoon as moisture
axis/short wave trough rotate through the area. Temperatures in
the low to mid 80s. Convection should diminish in the early
evening.

Friday and Friday night...Low-level moisture remains high
through the day especially in the east. Precipitable water only
decreases slightly. There appears to be a weak cold
front/moisture boundary moving south from eastern North Carolina
in the afternoon. Latest GFS/Nam suggest a few showers may
develop in the east again as another short wave moves through
upper trough, but appears more focused in the Coastal Plain
potentially aided by sea breeze convergence. The NBM pops are
quite low and mean CAPE lower than Thursday. Any convection
should be isolated. Temperatures a little warmer than Thursday.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Key Message(s):

-Drier into early next week with warming trend over the weekend

The ensembles continue to be in good agreement. Upper trough off
the east coast with upper ridge over the southern Plains
building east but flattening with time. Surface high ridging
down the Eastern Seaboard. Low-level moisture remains high,
high level moisture may increase by early Monday as the ridge
flattens. Ensemble qpf probabilities > 0.1 inch only 10-20 %
Sunday/Monday. NBM pops very low at this time so will continue
dry forecast.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
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Restrictions expected during the early morning through mid
morning hours.

Upper level low continues to spin over the terminals while
slowly moving eastward. Satellite and radar imagery shows a
couple showers across the area and with sunset the remaining
cells are beginning to diminish. Expect the showers to end by
03z with no impacts to the terminals with the main focus being
the early morning stratus and fog potential. With plenty of
moisture in the low levels and similar conditions to last night
expect another round of stratus and fog to develop with
indications for IFR and possibly LIFR around daybreak. Have
generally kept with previous thinking and adjusted times
slightly. Restrictions will begin mixing out shortly after
sunrise however will take until mid to late morning before all
sites return to VFR. Winds on Thursday generally becoming north
to northeast around 5 knots behind the departing upper level
system with skies clearing late in the period from west to
east.

EXTENDED AVIATION OUTLOOK...No significant impacts to aviation
expected through Monday.
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&&

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

&&

$$