Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 232052

Area Forecast Discussion
National Weather Service Columbia SC
452 PM EDT Mon Apr 23 2018

Slow moving low pressure will be in the region through Tuesday.
Moisture will be deepest into tonight associated with an
onshore flow ahead of the low. The low will be north of the
forecast area Wednesday and Thursday but a slow moving cold
front extending south from the low will linger in the area.
Another low pressure system will move through the area Thursday
night and Friday, with a possible third disturbance lingering on


The pressure gradient ahead of low pressure will result in
breezy conditions. Observation trends and the GFS LAMP support a
Lake Wind Advisory.

Moisture has become deep in the onshore flow ahead of
approaching low pressure with widespread showers. However, drier
air is rotating around the upper low and showers have ended
across the CSRA. Still, with a strong low- level jet and
possible training heavy rainfall rates may occur with some
possibility of localized flooding across the central and
northern Midlands. Expect general rain totals of 1.5 inches or

The potential for severe thunderstorms remains low, but has
increased south of a warm front that extends into Burke County.
Should the front shift northward this evening, storms could
move into the CSRA. Despite a lack of surface instability, high
shear associated with an h85 jet near 50 knots indicates some
potential for severe weather, including tornadoes. There will
also be enhanced instability as the upper lows gets closer and
upper-level temperatures cool, steepening lapse rates and
increasing hail potential. Mid-level drying overspreading the
area may also increase the downdraft potential. The SPC keeps
the CSRA and southern Midlands outlooked in a marginal risk.


Low pressure will continue slowly moving through the region
Tuesday and Tuesday night then accelerate northward to the
Atlantic Coast Wednesday.

A warm front will be lifting north of the Midlands at daybreak
Tuesday. By Tuesday afternoon...stacked low pressure over the TN
Valley will provide cold air aloft and the potential for
thunderstorms with locally heavy rainfall. The chance for
showers will decrease Tuesday night and Wednesday.

On Wednesday as the low moves away from the region focus will
turn to area rivers as significant rainfall across the Midlands
as well as the Upstate will continue moving through the system
with significant rises in river levels possible. Temperatures
will be in the 70s each day with overnight lows in the middle
to upper 50s.


Models remain in good overall agreement...though differences in
timing and intensity remain as features move through the forecast

An upper level trough over the eastern third of the nation will
finally move offshore late Saturday. An upper level ridge over the
central CONUS will build east across the region early next week.

At the surface a weak area of low pressure will develop along the
remains of the frontal boundary Thursday and quickly cross the area
Thursday night. Drier air will be over the area Friday with an upper-
level disturbance moving into the area Friday night and Saturday.
High pressure and drier air will move into the region Saturday night
through Sunday. This progressive pattern will keep chances of rain
in the forecast Thursday into Saturday. Dry weather is expected
Sunday and Monday as high pressure at the surface and aloft
returns. Temperatures are forecast to be near normal through
the long term.


Expect mainly IFR conditions through Tuesday morning, then a
slow transition to VFR by Tuesday evening.

Moisture has become deep in the onshore flow ahead of the slow
moving low pressure system. Observation trends and the models support
mainly IFR conditions during the period. Shear will be high
associated with an h85 jet near 50 knots. Shear is explicit
with breezy surface wind and gustiness in the forecast.
Isolated thunderstorms have developed in Georgia and could move
over the Augusta area after 23Z so have added -TSRA to the TAFs.
Thunderstorms should not reach Columbia or OGB.

Although heavy rain will end overnight, scattered showers are
expected through the day Tuesday.

Much drier conditions expected Wednesday. Another low pressure
system will bring restrictions Thursday and Friday.


GA...Lake Wind Advisory until midnight EDT tonight for GAZ040-
SC...Lake Wind Advisory until midnight EDT tonight for SCZ015-016-


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