Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 182253
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
553 PM EST Sat Nov 18 2017

.SYNOPSIS...
A cold front will move rapidly across the region tonight with
scattered showers and breezy conditions. A dry and cooler air
mass will build over the area Sunday and Monday. Moisture will
return mid to late week as the weak low pressure develops over
the Gulf of Mexico.

&&

.NEAR TERM /THROUGH SUNDAY/...
A positively tilted upper trough over the Mississippi Valley
this evening will move across the region overnight and into
Sunday. Shortwave trough appears to weaken as it crosses the
area with stronger dynamics to our north. The trough will push a
cold front through the area late tonight. Front appears to move
through the area between 06Z and 10Z with scattered showers. Of
concern is the very strong low-level shear with 60 kts at 850
mb. Instability appears very limited however with SREF most
unstable cape around 50 j/kg. Little support for thunderstorms
noted in nam/gfs operational runs. Moisture appears to be a
limited factor as well with maximum precipitable water 1.5
inches. Highest pops in the Piedmont and North Midlands where
upper-level forcing may be stronger. Gusty winds expected
overnight with strong mixing and a lake wind advisory may be
needed. The showers are expected to clear the Midlands and CSRA
by 12z Sunday. Temperatures should remain mild ahead of the
front because of mixing...with lows from the upper 40s west to
the mid 50s east.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
On Sunday expect cold advection and clear skies. Breezy
conditions thru the morning, with diminishing winds during the
afternoon as the pressure gradient relaxes. Daytime highs will
be mostly in the lower 60s with downslope flow offsetting cold
advection somewhat. Temperatures near freezing in some areas
Sunday night especially northern and central counties. Patchy
frost possible may be possible elsewhere late Sunday night.
Dry and cooler air mass over the area Monday with temperatures
ranging from around 60 north to the lower 60s south.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
The upper level pattern remains somewhat amplified later in the
week, but large model differences result in a lower than normal
confidence forecast. Latest GFS and Canadian models are leaning
toward some sort of low pressure development in the Gulf of
Mexico with a cut-off upper low over the Gulf states by Thursday.
Moisture appears to focus early along old frontal boundary
across Florida to the Georgia and Carolina coastline. Will keep
a small chance for rain mid to late week including Thanksgiving
although confidence remains low with large spread in guidance.
Leaning toward cooler than normal for Thanksgiving given the
pattern and possibility of rain. Overall, temperatures generally
near normal through mid-week, then below normal through
Saturday.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
A cold front will move through the area tonight. A strong low-
level jet will be associated with the front. The models
indicated 2000-foot wind 45 to 55 knots. We have included low-
level wind shear in the TAFS. The high-resolution models and
radar trends support showers in the area during the 06z to 11z
time frame. Increased mixing in showers supports some of the
wind mixing down. The NAM Bufkit momentum transfer tool
suggested gusts 25 to 30 knots may occur. The models and
upstream observations support a period of MVFR ceilings and
visibilities in showers. Expect clearing behind the front
beginning around 12z. The NAM and GFS MOS support northwest
winds 10 to 15 knots after 12z.

EXTENDED AVIATION OUTLOOK...Dry high pressure will be centered in
the region Monday. An onshore flow will develop Tuesday as the high
shifts farther off the coast. An area of low pressure may develop
near the Southeast Coast during the middle of the week. IFR or MVFR
conditions may occur Tuesday through Thursday.

&&

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

&&

$$
SYNOPSIS...99
NEAR TERM...99
SHORT TERM...99
LONG TERM...99
AVIATION...99


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