Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 211127

Area Forecast Discussion
National Weather Service Columbia SC
627 AM EST Tue Feb 21 2017

Above normal temperatures expected through the period. Today
will be dry but cloudy as high pressure shifts offshore ahead
of an approaching system. Increasing moisture and isentropic
lift will bring a chance for showers tonight into Wednesday.
The chance for a few showers will linger into Saturday. A cold
front will cross the region Saturday with dry high pressure
building into the area for the start of next week.


High clouds will continue to increase as upper ridge axis shifts
east and next weather system approaches. Mid and low clouds will
also increase today as southeast flow brings low-level moisture
and isentropic lift. By this evening, an upper low will be
centered over the lower Mississippi valley, and pre-frontal
showers could begin moving into the CSRA. Temperatures will once
again be above normal with highs in the 70s.


Upper and surface ridge will be located off off the coast
tonight as an upper low tracks southeast across the Gulf of

An onshore flow...with increasing isentropic lift and moisture
transport will bring a chance for showers. Have indicated the
highest pops across the western part of the forecast area with
slight chance pops east tonight through Wednesday.

Most of the guidance indicate higher rainfall coverage and
amounts to our north enhanced by orographic lift and a weak in
situ edge, though some additional showers could develop in
diurnal heating/differential heating across the forecast area
Wednesday afternoon. With possibility of weak wedge affecting
the North Midlands and Piedmont, kept daytime highs a little
cooler...around 70. Should see high temperatures in the low to
mid 70s for the remainder of the forecast area. Went near
guidance consensus for overnight lows in the 50s tonight and
Wednesday night.


The models take the closed low near the Florida Keys on Thu
through the Bahamas on Friday. Surface high pressure off the
Carolina coast will ridge into the region with building heights
aloft. The weak in situ wedge may linger just to our north
Thu. A moist E to SE low level flow to provide a continued
chance of showers, enhanced by diurnal heating, Thu aftn.
However, by Thursday, some drier air aloft may move into the
region and cut down on overall shower chances.

The next cold front will be crossing the MS River Valley Friday
with a nearly zonal flow across the southern tier of states.
The long term models are in agreement with this front crossing
the area Saturday. Chance pops appear ok with the front.
Surface high pressure and drier air will settle into our FA late
Sat through Sun. Modified Pacific air mass with cooler temps
but still projected to be above normal. Nearly zonal upper flow
across the southern states expected to continue late in the
forecast period as well, with systems moving rapidly. A quick
moving trough will track east across the country, with it and
the surface low staying to our north. Surface high to shift east
ahead of it Sun night into Monday, with moisture return for our
area Mon/Mon night into early Tue. Any chance for precipitation
will be low.


Expect mainly VFR conditions through the day, with MVFR/IFR
restrictions this evening and overnight due to increasing

High clouds will continue to stream in from the west in advance
of the next weather system. There is some patchy fog and stratus
this morning that should burn off after sunrise. Low-level
moisture will increase with a southeast onshore flow, and isentropic
lift will allow stratocumulus to develop during the day. The
clouds will increase and lower during the late afternoon and
evening, causing MVFR conditions during the evening, and then
IFR conditions overnight. Light showers will also move through
the area tonight, and fog is expected by Wednesday morning.

EXTENDED AVIATION OUTLOOK....Moisture associated with an
onshore flow may help bring widespread MVFR or IFR conditions
through Friday.




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