Area Forecast Discussion
Issued by NWS Columbia, SC

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399
FXUS62 KCAE 051137
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
637 AM EST Tue Nov 5 2024

.SYNOPSIS...
High pressure will extend into the area from the northeast.
Scattered light rain expected today due to moist onshore flow. A
frontal boundary will approach from the northwest Wednesday into
Thursday. As tropical storm Rafael moves northwest toward the
Gulf of Mexico Wednesday from the Caribbean Sea, deep moisture
is expected to spread north into the Georgia and South Carolina.
This will lead to numerous showers late Wednesday into Thursday.
Locally heavy rain will be possible. Moisture may linger into
the weekend but showers will become more isolated. Temperatures
are expected to be above normal.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Message(s):

- Scattered showers, especially in the Midlands today.

Scattered light showers and drizzle mainly in South Carolina
counties this morning as onshore flow and isentropic lift continues
over the forecast area. This has led to widespread low cloudiness as
well. Temperatures remain on the warm side this morning as a result,
in the mid 60s.

Plentiful moisture today in the low and mid levels with a narrow
band of highest PWATs between 1.4 to 1.5 inches over the Midlands.
While overall lift will be relatively weak, there will be enough
isentropic lift to support scattered showers. Surface high pressure
remains centered near Bermuda which will continue to support onshore
flow. As it moves slowly east, the strongest lift will shift a bit
to the east as well where a surface trough will promote low level
surface convergence. While rainfall amounts will not be overly
impressive, HREF indicates high probability of at least a quarter
inch today, centered along the I-26 corridor, which is substantially
more rain than we`ve seen since late September. Precipitation
expected to taper off tonight as isentropic lift weakens.

Upper ridging remains over the area with 500mb heights well above
average with NAEFS mean near the 99th percentile. This combined with
the warm start to the day will lead to above average temperatures
today with highs in the mid 70s to around 80, even with clouds and
scattered showers. Lingering low clouds tonight with low
temperatures remaining warm once again, in the low to mid 60s.

&&

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

- Moderate rainfall expected. Locally heavy rain possible.

Upper ridge off the coast of the Southeastern states with
increasing southwest flow aloft.  The surface ridge will be
well east of South Carolina. Tropical storm Rafael is expected
to be moving northwest through the northern Caribbean Sea
during the day. Ensembles and deterministic models continue to
show a plume of moisture ahead of the storm spreading north
across the eastern Gulf of Mexico into Georgia and South
Carolina. GEFS and EPS show precipitable water increasing to
above 2 inches with highest confidence across the CSRA and
southeast/central Midlands. This is also now supported by the
HREF. So expect precipitable water near 300 % of normal by
Wednesday night into Thursday morning. The axis of deeper
moisture shifts to the east a bit Thursday. A frontal boundary
will be approaching from the northwest Wednesday night and may
set up across the area, likely enhancing low level convergence.
Models show increasing isentropic lift/moisture flux with
onshore flow late Wednesday into Thursday. Additional lift
provided by weak mid level short waves in southwest flow aloft.
Raised the pops a bit from previous forecast and trending toward
widespread showers with highest confidence in the CSRA. WPC has
put CSRA into the central Midlands in a slight risk of
excessive rain. Ensemble QPF means are high but the
distributions show large spread. Ensemble guidance mean total
qpf 2-3 inches especially CSRA but median values a little lower
due to positive skewness leading to outliers. Despite dry
pattern of the last 30 days, there appears to be an elevated
risk for excessive rain especially in the CSRA. The showers are
expected to shift to the east Thursday afternoon. Temperatures
will be still above normal despite rain and clouds.

&&

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

- Lower chances for showers but low confidence forecast.
- Temperatures remain above normal.

Flat upper ridge over the southeast with confluent flow to the
north. Deep low in the Desert Southwest moving into the Plains
over the weekend. Expect surface ridge to be build south into
the Carolinas from the north. Front near the area Friday,
possibly near the coast. Tropical Storm expected in the Gulf of
Mexico. Scattered showers expected Thursday night. Ensembles
keep lingering moisture across the area into the weekend but
precipitable water slowly decreases. Uncertainty high early in
the weekend due to tropical system in the Gulf. NBM keeps low
pops into early next week with above normal temperatures.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
IFR Ceilings with Occasional Visibility Restrictions this
Morning. Restrictions Redevelop Tonight.

IFR ceilings are in place at all terminals this morning with
scattered showers also leading to decreased visibility at times.
As the plume of moisture over the terminals slowly shifts
eastward, expect decreasing chances for rain and improving
ceilings mid to late morning into the afternoon. VFR conditions
expected at all terminals by mid to late afternoon with cumulus
deck around 4kft. Tonight, while some drier air will likely move
in aloft, lingering low level moisture will once again support
restrictions developing. Uncertainty among models as to whether
IFR or MVFR restrictions but based on persistence, mostly
favored IFR ceilings.

EXTENDED AVIATION OUTLOOK...Early morning restrictions
continue to be possible as onshore flow continues into midweek.
Increasing chance for rain and associated restrictions for the
second half of the week.

&&

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

&&

$$