Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 222228

Area Forecast Discussion
National Weather Service Columbia SC
628 PM EDT Thu Aug 22 2019

High pressure in the Atlantic will direct a moist, south
flow into the forecast area through Friday. An approaching cold
front will move into the region Saturday. The front will stall
just south of the area Sunday.


Thunderstorms may linger in the extreme north Midlands this
evening with convection moving northeast from the Piedmont.
However, overall Satellite/Radar and Obs trends suggest
weakening and dissipation over the next couple of hours. Partly
cloudy with convective debris with temperatures falling into the
low to mid 70s. Fog limited by strong low-level jet.


The main concern is possible localized flooding associated with
the cold front interacting with high moisture in the forecast
area. NWS`s Weather Prediction Center has the outlooked for a
marginal risk of excessive rainfall beginning Friday night into
Saturday. The 1 hour flash flood guidance is generally from 1.5
to 2.5 inches and the 3 hour flash flood guidance is generally
from 3 to 5 inches. These values will be slightly lower as we
move into Saturday/Saturday night with expected rainfall this
afternoon through Friday.

High pressure off the Southeast Coast will continue to direct
moist air into the forecast area ahead of the approaching
backdoor front Friday and Friday night. The models depict a more
pronounced lee or pre-frontal trough. Expect an increasing
chance of showers and thunderstorms. The NAM and GFS forecast
precipitable water 2.0 to 2.3 inches. This moisture and possible
training of showers and thunderstorms indicates the potential
for locally heavy rain and the possibility of localized
flooding. Moderate instability is forecast Friday afternoon and
evening so a few thunderstorms could also contain damaging wind.

The front is forecast to extend through the forecast area
Saturday. The GFS and ECMWF show the front pushing just south of
the area Saturday night. Precipitable water is forecast to
remain high at 2.0 to 2.3 inches. The models suggest the
heaviest rain Saturday and Saturday evening. We forecasted
general rain totals around 1.0 to 1.5 inches. Higher amounts
will occur showers and thunderstorms possibly training along
the east-west oriented front. As mentioned above, there will be
an increased threat for localized flooding and some flooding of
smaller streams.


The GFS and ECMWF show the front will push south of the region
by Sunday and linger just south of the area through Monday night
into Tuesday. By Monday night into Tuesday, both the GFS and
ECMWF try to lift the front northward as it diminishes. High
pressure wedging into the area just behind the cold front may
bring below normal high temperature Sunday and Monday. The
models have indicated areas of low pressure developing along the
front, but have kept these features off the coast. We followed
a guidance consensus for the pop and temperature forecast. By
Tuesday night into Wednesday another cold front will approach
the area from the northwest, bringing with it another increased
chance for showers and thunderstorms. Some drying expected by
Thursday. Temperatures will begin to moderate as the wedge type
setup gradually weakens into early next week.


VFR conditions expected outside of any isolated afternoon and
evening convection.

Skies have filled in somewhat this afternoon, becoming scattered
to broken in the mid-levels. A weak shortwave moving through
eastern GA and into SC has been enough to trigger some isolated
showers across the cwa this afternoon. CAE/CUB are the two main
taf sites currently being impacted by this activity, and have
included vcts and tempo group for storms. Activity and outflows
may be enough to bring activity close to OGB later this
afternoon, and have included vcts at that site after 19z. At the
CSRA sites of AGS/DNL, have held off on any precip due to the
shortwave being almost over them, thus best activity should
remain off to their east. Winds will continue generally out of
the west through the day at 5 to 10 knots or less, but will also
be variable near storms and outflows. Late tonight, the fog
threat will once again be limited by a 20 knot low level jet and
drier low level air.

EXTENDED AVIATION OUTLOOK...Widely scattered diurnal
thunderstorms Friday afternoon. Increasing thunderstorm chances
Saturday associated with a cold front. The front may stall near
or just south of our region Sunday into early next week, and
may provide good chances of rain and associated restrictions.




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