582
FXUS62 KCAE 240021
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
821 PM EDT Mon Sep 23 2024

.SYNOPSIS...
High pressure building over the SE US will keep warm conditions
over the Southeast into the first half of the work week.
Multiple shortwaves crossing the region will bring chances for
precipitation through much of the week. Confidence remains on
the lower side in the forecast beyond midweek as there is still
uncertainty associated with the evolution of an upper trough
moving toward the region and the track of a likely developing
tropical system in the Gulf.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Key Message(s):

- Isolated convection may linger through the near term

Water vapor imagery shows a shortwave working over the top of a
ridge centered to our south. This shortwave will allow
convection to persist through the evening and possibly into the
early morning. The RAP shows elevated instability over the area
of around 1000 J/kg through the night supporting the chance of
thunderstorms. Storm movement will be fast enough to limit the
threat of flooding and stable low levels should prevent wind
gusts.

Light northerly winds at the surface will help advect slightly
cooler air into the northern forecast area. This should yield a
similar setup to the previous morning with low stratus over
northern portions of the area. Temperatures will be mild
overnight with lows in the upper 60s to low 70s.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Key Message(s):

- Upper ridge continues to bring above average temps.
- Marginal Risk for Severe Weather Tuesday Afternoon and Evening
  north of Columbia.

The upper level ridge axis will shift slightly eastward Tuesday with
above average temperatures continuing. Models do indicate the
potential for lingering stratus through the morning across the
northern portions of the forecast area once again, so there will be
at least somewhat of a temperature gradient with highs in the low
90s in the south to mid 80s across the north. Bit of a question mark
as to the development of showers and storms Tuesday afternoon as
HREF mean soundings show the potential for a capping inversion
across the area, but also weaknesses in the ridge and some weak
convergence across the northwestern portions of the area. As a
result, isolated to widely scattered showers and storms are
possible with highest coverage in the NW. Some of these storms
may be a bit organized with deep layer shear approaching 30
knots near the SC/NC border. A marginal risk for severe weather
remains in place north of Columbia.

The upper ridge continues to shift eastward Wednesday with a
deepening trough over the lower Mississippi Valley that there
remains good consensus among models will develop into a cut-off low
pressure system. Even some of the faster guidance keeps an impacts
from PTC Nine well to our south through Wednesday. This will lead to
fairly uneventful weather Wednesday with temperatures above normal,
although likely a few degrees cooler than Tuesday and little chances
for rain.

&&

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

- Likely tropical system continues to develop in the Gulf, but
  uncertainty remains in its track.
- Chances for precipitation increase toward the end of the week.

National Hurricane Center is issuing advisories on Potential
Tropical Cyclone Nine. High confidence that PTC 9 will develop into
a tropical cyclone in the northwest Caribbean or southeast Gulf of
Mexico and move north towards the Gulf Coast. Increasing confidence
in the storm making landfall as a hurricane but uncertainty remains
in the track as it interacts with an upper low moving in the
Mississippi Valley. Most guidance (global models and ensemble
members) do generally take the center west of the area but exact
impacts depends on how close the center moves towards the area
and the degree of weakening as it moves inland. For now, the
biggest impact will likely be moderate to potentially heavy
rainfall that could develop as early as Thursday afternoon,
although most ensemble members at this point favor heaviest rain
Thursday night. With the current track of the storm, however,
tornado potential as well as strong winds are possible with
ensemble guidance indicated highest potential for gusts above
40mph in the CSRA (around 50 percent chance probability).

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
VFR conditions expected through at least 06z. IFR ceilings at
CAE/CUB developing toward morning.

Scattered to broken cumulus across the area this evening. Radar
indicating a few showers and thunderstorms in the area. Widely
scattered showers moving over an upper ridge may continue into
the overnight as suggested by the HRRR. But based on radar trends,
the showers are not expected to impact terminals at this time.
Low clouds to the north of the area near the SC/NC border are
expected to move south into central SC late tonight. The highest
probability of restrictions appears to be at CAE and CUB. Will
continue previous forecast of IFR ceilings at these sites.
Otherwise, MVFR fog may develop at OGB and AGS toward daybreak.
Focus for showers on Tuesday appear to be north and west of the
area with upper ridging in the area limiting development.
Scattered to broken cumulus/alto cumulus through the day. Winds
mainly south or southwest less than 10 knots.

EXTENDED AVIATION OUTLOOK...Restrictions along with strong
winds becoming possible Thursday through Saturday associated
with a potential tropical system moving west of the forecast
area.

&&

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

&&

$$