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000
FXUS62 KCAE 221501
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
Issued by National Weather Service Greenville-Spartanburg SC
1001 AM EST Tue Jan 22 2019

.SYNOPSIS...
Cold high pressure ridging into the forecast area this morning
will shift off the coast today. Moisture will increase in the
veering east to south flow on the backside of the offshore high
and ahead of a cold front tonight and Wednesday. There will be
increased cloudiness and spotty areas of light rain late tonight
and Wednesday. The front will be in the area Wednesday night
into Thursday morning and showers will occur. High pressure
following the front will dominate Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Skies are almost completely clear this morning with light
easterly surface flow around surface ridge northeast of the
area. Very dry dewpoints will increase this evening as surface
flow becomes more southeasterly. This will also increase high
temperatures about 4 degrees over what was seen on Monday. As
next upper system approaches, some light rain becomes possible
Tuesday night/Wednesday morning.

Believe there will be increased low cloudiness and a chance of
light rain or drizzle late. The guidance consensus supports pops
around 30 percent. The NAM, GFS, and ECMWF depict very little
QPF, about 0.01 of an inch. The NAM continues to be the coldest
in the near-surface layer indicating a concern for freezing rain
in the north section. It has had a cold bias this winter. We
followed the more consistent GFS and ECMWF which have surface
wet bulb temperatures above freezing even in the extreme north
section. Also, precipitation will be light with limited
evaporative cooling potential. Nearly all SREF members keep
temperatures above freezing. We believe the chance of freezing
rain is too low to include in the forecast at this time.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
Wednesday will start cloudy as increasing low level moisture
and isentropic lift support plentiful low clouds through the
first half of the day. There will be some light rain or
sprinkles around, but little if any QPF is expected with
significant dry air once you get above 6K feet, not allowing
much depth to the stratus/stratocu.

By afternoon, winds will turn southerly and increase, and some
breaks may develop as mixing increases ahead of the approaching
cold front. Temps will be noticeably warmer by afternoon, with
maximum temps ranging from 60 near the NC border to 70 in the
southern CSRA.

Wednesday night...the cold front will rapidly move through the
area. Despite its speed, a decent amount of rain will fall due
to a combination of much above normal deep moisture (PW values
more than 1.5 inches), strong diffluence aloft in the right rear
entrance region of a jet, and strong mid level lift from an
approaching sharp trof and associated vorticity. Rainfall
totals will generally be around an inch, but local areas could
see double that amount. Temps will be much above normal for
most of the overnight, although it will start to cool towards
daybreak as winds turn westerly behind the front and cold
advection begins.

Thursday...The front will continue its rapid trip eastward into
the western Atlantic Ocean. There may be some lingering showers
in the morning, most likely in the eastern half of the FA, but
the chances of rain will essentially end by mid morning in the
western and central areas, and noon everywhere. Temperatures
will not change much during the day as the increasing sunshine
will be counteracted by surface cold advection behind the front
on cool northwesterly flow.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
High pressure will move into the region for Friday and Saturday.
The air mass origin will be more continental than polar, so I
don`t expect a true arctic invasion, but temps will nonetheless
fall back to a little below late January norms.

For Sunday and Monday, the ECMWF and FV3 have come into much
better agreement with the GFS, as all models are advertising a
much flatter system coming out of the Gulf of Mexico, passing
well to our east. The Canadian is now the lone outlier keeping a
stronger low closer to the coast and threatening the area with
precipitation. I have lowered POPs considerably for Sunday
through Monday, but not all the way to zero in deference to the
Canadian, along with a couple of the GEFS members that still
bring in some rain.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
We have high confidence in VFR conditions through today. Low-
level wind shear along with lowering ceilings will occur tonight.
IFR ceilings may develop toward the end of the 24-hour TAF
period.

It will remain dry today because of the pressure ridge in the
region. VFR conditions should continue. The surface ridge will
be shifting eastward and bring easterly winds. The NAM and GFS
MOS support speeds 5 to 10 knots.

Moisture will increase tonight with continued onshore flow
associated with the offshore high and ahead of a cold front well
to the west. Expect a ceiling will develop and lower overnight.
We followed the GFS MOS for the timing of developing MVFR and
IFR ceilings. There is a diminished fog risk because of the
cloudiness and a continued dry near-surface layer.

The moisture should remain too shallow for rain through 06z
because of the lingering affects of upper ridging. The moisture
may become just deep enough for areas of drizzle or light rain
after 06z. Uncertainty was too high at this time to include the
precipitation and possible visibility restrictions in the
terminals at this time.

There will be increased shear associated with a low-level jet
developing ahead of the front. Followed the NAM and included
low-level wind shear in the terminal forecasts beginning around
04z.

EXTENDED AVIATION OUTLOOK...
MVFR/IFR conditions are likely Wednesday morning. The cigs could
lift to VFR by afternoon, especially at AGS and DNL, as mixing
increases, but it will come at the cost of slightly stronger
southerly/southwesterly winds.

Wednesday night as the front moves through, expect IFR
conditions in clouds/rain. LLWS could also be a problem with
the models forecasting winds in excess of 50 knots as low as 2K
feet near the front.

Thursday conditions will be improving from west to east as the
front moves away, with VFR conditions likely at all terminals by
some time during the afternoon. VFR conditions are then expected
to continue into the weekend.

&&

.HYDROLOGY...
Minor flooding will continue on the Congaree River due to recent
rainfall and upstream reservoir releases within the Broad and
Saluda River basins.

&&

.EQUIPMENT...
The Columbia, SC (KCAE) WSR-88D is out of service due to a
faulty voltage regulator. The part will be ordered but an
estimated time of arrival is unknown at this time.

&&

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

&&

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