Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 171129
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
629 AM EST Tue Jan 17 2017

.SYNOPSIS...
Weak cold air damming will weaken today as surface ridge moves
off the coast. A weak cold front will move through the region on
Wednesday with widely scattered showers. As low pressure moves
northeast from the lower Mississippi valley late
Thursday...showers will spread into the region. Although cool
temperatures possible Thursday...temperatures through the week
should be above normal at times. Unsettled weather continues
into the weekend with rain chances increasing.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
In-Situ Cold air damming continues early this morning with
ridge over North Carolina extending into the area. Widespread
dense fog appears to be developing across the region this
morning based on latest surface observations. Will expand Dense
fog advisory through the rest of the CWA. Patchy drizzle has
been reported and likely thru the area through at least
daybreak. Models in fair agreement that ridge will weaken/move
off the coast and wedge will erode through the day from
southeast to northwest. Temperature forecast confidence high in
the CSRA and lower in the north Midlands. But think clouds
decreasing in the afternoon with southwest low level flow and
moisture becoming more shallow. This should result in warmer
temperatures today...above normal with low 70s into the central
Midlands.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
Upper low over the Ohio Valley late tonight will move southeast
across the Mid Atlantic region and upper ridge over the
Southeastern States will weaken. The trough will drive a weak
cold front through the area during the day Wednesday. Although
increase in precipitable water noted...lack of surface
convergence and downslope flow should result in limited showers
in the area. Forcing appears strong to the north of the area.
Will continue slight chance pops associated with frontal
passage. Temperatures warmer...due to downslope flow and
clearing in the afternoon.

Upper flow backing Thursday ahead of deepening low in the
lower Mississippi Valley. Surface ridge over the Carolinas.
Moisture appears to increase rapidly during the day...and a few
showers may develop mainly in the CSRA/west Midlands. Weak in-
situ wedge may develop although surface winds more east-
southeast in the afternoon. Increasing clouds should result in
cooler temperatures...especially north Midlands. Went below
guidance for highs in the north. Large temperature gradient
possible and confidence low.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A very active southern branch of jet stream will push two systems
into the Southeast U.S. late this week into early next week.  The
first system arrives Thursday Night into Friday with the second
system...possibly strong...forecast for Sunday into Monday with
a thunderstorm threat. Expect unsettled weather and for the
most part above normal temperatures during this time period.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
High confidence for cig/vsby restrictions through late morning.

A moist easterly flow coupled with abundant low level moisture
trapped beneath an inversion will hold mainly IFR/LIFR
conditions across the TAF sites through late morning, although
some improvement in conditions has noted at CUB and DNL.
Overall should see improving conditions after 16Z with VFR
conditions returning during the afternoon with mixing as winds
become southwest around 10 knots. Patchy fog may be an issue
early Wednesday morning across the area given the latest model
guidance, but not enough confidence to mention in the TAFs at
this time.

EXTENDED AVIATION OUTLOOK...Late night/early morning fog
possible through Saturday. Showers and associated restrictions
possible Thursday through Saturday.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...Dense Fog Advisory until 10 AM EST this morning for GAZ040-
     063>065-077.
SC...Dense Fog Advisory until 10 AM EST this morning for SCZ015-016-
     018-020>022-025>031-035>038-041.

&&

$$



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