Area Forecast Discussion
Issued by NWS Columbia, SC

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669
FXUS62 KCAE 281508
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
1008 AM EST Tue Feb 28 2017

.SYNOPSIS...
A warm southerly flow between offshore high pressure and an
approaching cold front will continue through Wednesday. The cold
front will move through the forecast area Wednesday night.
Thunderstorms may be associated with the front late Wednesday
afternoon and night. It will be windy just ahead of the front
Wednesday. Cooler conditions will follow the front for the end
of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Expect mostly sunny skies and temperatures well above normal.
The temperature guidance was consistent with highs mainly in the
lower 80s and just below records for the date. Previous model
runs incorrectly indicated widespread clouds over the area this
morning. This will allow temperatures to rise more quickly than
guidance previously suggested. Increased high temperature
values a few degrees to account for the additional daytime
heating.

Moisture has become shallow behind the mid- level shortwave
trough that has moved through the forecast area. The models
indicate moderate instability today. The NAM has surface- based
LI values -5 to -6 but with just shallow moisture and the
dissipating surface feature the thunderstorm chance is very low
as supported by the NAM, GFS, and ECMWF MOS plus high-
resolution models.

The shower and thunderstorm chance should remain very low
tonight with continued shallow moisture and much of the lift
associated with a mid-level shortwave trough staying north of
the forecast area. Low-level moisture and weak isentropic lift
may lead to stratus and fog tonight with stratus favored because
of boundary layer wind. Warm advection and mixing should help
hold up temperatures. The temperature guidance was close with
lows around 60.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
The main issues Wednesday will be windy conditions ahead of a
cold front and possible severe thunderstorms late Wednesday
afternoon and night.

The models depict a strong low-level jet ahead of the cold front
Wednesday with h85 winds 40 to 50 knots. There should also be
strong warming and instability ahead of the front. The NAM
displays surface-based LI values around -6. Associated strong
mixing should lead to windy conditions. The NAM Bufkit momentum
transfer tool supports gusts near 30 knots Wednesday afternoon.
A lake wind advisory will likely be needed. Convergence ahead of
the front may lead to a band of showers and thunderstorms and
with continued high shear and possible moderate instability
lingering into the night severe thunderstorms may occur. A
limited factor may be mid-level capping as shown by the NAM and
GFS during the day Wednesday and diminishing instability with
the loss of heating Wednesday night. The SPC WRF indicated a
diminishing area of showers and thunderstorms moving into the
forecast area Wednesday night. Drying behind the front should
dominate Thursday.

Leaned toward the higher temperature guidance ahead of the front
Wednesday. A near record high for the date should occur. The
higher guidance may be better Wednesday night because of mixing
associated with the front. Followed the guidance consensus
temperature Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The GFS and ECMWF show dry high pressure building into the
forecast area from the northwest through Friday with the high
near the area Saturday and off the coast Sunday and Monday. The
GFS and ECMWF plus GFS ensemble mean have pops less than 20
percent through Sunday, and 20 percent or less Monday. The MOS
indicates the coldest air Sunday with lows near freezing.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
Restrictions will be possible again early Wednesday in mainly
stratus.

Expect VFR conditions throughout the day with a mostly sunny
sky and light S winds through mid-day becoming SW this afternoon
just under 10 kts.

Cannot rule out an isolated shower this afternoon although
chances are much too low to include given limited moisture and
weak dynamics. Models indicate potential for stratus and fog
beginning around 06Z Wednesday morning. However, a 25 to 30 knot
low level jet will promote mixing, so expect mainly stratus
development.

EXTENDED AVIATION OUTLOOK...Periods of MVFR/IFR restrictions
Wednesday morning through Thursday in unsettled weather with
occasional showers and thunderstorms.

&&

.CLIMATE...
Records for the date...

February 28...AGS 86 set in 1962
              CAE 84 set in 2011

March 1.......AGS 85 set in 1997
              CAE 83 set in 1997

&&

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

&&

$$



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