Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 202253

Area Forecast Discussion
National Weather Service Columbia SC
553 PM EST Tue Feb 20 2018

Much above normal temperatures will continue through the end of
the week. High pressure centered off the coast will bring warm
and moist air into region through Saturday. A cold front will
cross the region late in the weekend into early next week,
bringing a better chance for showers and slightly lower


Some decrease in cumulus clouds early this evening however
latest satellite showing increase in strato-cu across the low
country spreading north associated with shallow moisture
flux/isentropic lift.

Abundant low level moisture in place and the persistent onshore
flow off the atlantic will keep moisture high beneath mid level
dry air through the overnight. This will set the stage for
another potential night of fog/stratus redevelopment and another
dense fog advisory may be required Wednesday morning although
stronger low-level jet tonight may favor stratus.

The high dewpoints along with developing stratus/fog
will keep temperatures mild overnight and well above normal.
There is a possibility we could tie or break the record warmest
minimum for Feb 21 (60 is the record) with forecasts of lower
60s tonight.

A weak upper disturbance rotating around the upper ridge will
lift through central GA into the Upstate overnight and could
bring a few showers with it, but expect these to remain to the
west of the forecast area.


Upper level disturbance will continue moving through the Upstate
and away from the forecast area through the day with high
pressure and the upper level ridge dominating the area. Fog will
burn off during the morning hours with skies becoming partly
cloudy toward early afternoon. As temperatures rise through the
morning hours expect any area which breaks out of the clouds to
quickly develop cumulus and become partly to mostly cloudy.
Models have kept the upper level disturbance further west of the
forecast area so have decreased pops for Wednesday resulting in
no rain expected across the area. With plenty of low level
moisture across the region Wednesday night will again see patchy
fog development...possible locally dense. High pressure and the
upper level ridge will again dominate the region for Thursday
keeping a frontal system to the northwest of the area. With
southerly flow at the surface and aloft plenty of moisture will
remain over the forecast area with skies again partly to mostly
cloudy. Areas which break out from morning fog will quickly warm
with cumulus developing...however with a strong cap aloft
vertical development of cumulus will be limited so no rain is
expected. Temperatures will be in the upper 70s to low 80s for
daytime highs and upper 50s to low 60s for overnight lows.


Highly amplified upper level pattern will remain from the
central Pacific through the western Atlantic through Saturday
then begin breaking down into early next week. This will keep
the surface high pressure off the coast of the Carolinas and
the upper level ridge over the eastern US through Saturday. with
the high dominating at the surface low level winds will remain
southerly allowing ample moisture to persist over the region
with partly to mostly cloudy skies and potential for early
morning fog each day. The next cold front is expected to cross
the region Sunday or Sunday night then stall along the coast
into next week. Models have some timing differences with this
system with the GFS being more aggressive than the ECMWF. With
the timing differences have remained with chance pops for Sunday
onward. Much above normal temperatures will continue with highs
in the upper 70s and lower 80s are expected to moderate to the
upper 60s to mid 70s for Monday and Tuesday.


High confidence in VFR conditions into this evening and then
expect conditions to deteriorate again later tonight in
fog/stratus after 06z.

Persistent southerly low level flow will keep low level moisture
high over the region with dry air at the mid and high levels,
which are favorable conditions for fog development. Bufkit time
heights show a 20-25 knot low level jet which may favor stratus
more than fog and therefore confidence is a bit lower on dense
fog developing but all guidance suggesting it will redevelop.
Bring cig/vis back down to MVFR/IFR/LIFR starting around 06z-08z
with LIFR cigs all terminals by 09z. Similar to today
conditions will be slow to improve until mid morning so will
show a gradual improvement after 15z, with VFR conditions
returning by around 19z.

EXTENDED AVIATION OUTLOOK...Widespread IFR stratus and fog may
occur during the early morning hours over the next few days due
to high low-level moisture in an onshore flow.




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