Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 091129

Area Forecast Discussion
National Weather Service Columbia SC
629 AM EST Fri Dec 9 2016

Cold high pressure will build into the area through Saturday with
no chance of rain. The ridge will shift off the coast Sunday and
temperatures will begin to moderate as rain chances increase early
next week as a cold front moves into the region.


Expansive cold Canadian high pressure centered along the Plains
states will continue to build into the forecast area today and
tonight. Cold advection continues today with 850mb temps around
-4C to -6C with no chance of rain due to a very dry airmass in
place with precipitable water values around 0.10 inches and
dewpoints in the teens. The weakening upper trough axis will cross
the region today but the atmosphere is too dry to support any
precipitation and even skies likely to be cloud free.

Temperatures will be around 10-15 degrees below normal with highs
in the 40s and lows overnight in the lower to mid 20s. Continuing
to forecast temps slightly below guidance as trends have been
cooler with time from the MOS and local temperature scheme
supports values slightly colder.


Cold but fair weather will continue on Saturday with surface high
pressure centered over the region with zonal westerly 500mb flow
aloft. Temperatures will be similar despite slight warming at
850mb due to lack of deep mixing on Saturday. Highs expected in
the 40s to lower 50s and lows Saturday night slightly warmer in
the 20s.

Sunday the surface ridge will shift offshore allowing a return
southeasterly low level flow off the Atlantic which will increase
moisture and isentropic lift should support increasing clouds.
Think any precipitation will hold off due to weak isentropic
lifting and marginal moisture with precipitable water values only
rising to just over a half inch, but cannot rule out a few
sprinkles Sunday afternoon. Temperatures will be moderating a bit
on Sunday with highs expected in the 50s.


Uncertainty and low confidence continue to be the theme in the
extended periods as medium range models continue to struggle with
handling of northern stream energy and timing of a series of front
expected to move into the forecast area next week. There is
reasonable confidence that a cold front will push into the
forecast area sometime on Monday into Monday evening but
differences arise with what happens to the front.

The GFS is more progressive pushing the front through and
stalling south of the area on Tuesday before shifting back north
as a warm front on Wednesday before the next stronger front pushes
through late Wednesday into Thursday. The ECMWF and Canadian
models push the front into the region on Monday and stall it over
the forecast area lingering chances of rain through the day
Tuesday with the boundary in the vicinity followed by increasing
chances Tuesday night into Wednesday ahead of the next front.

The ensemble guidance shows significant spread in the pops and
temperatures during this entire period with 20-25 degree
temperature ranges and pops ranging from 10 percent to 70 percent
during some periods, leading to below normal confidence. Therefore
made little changes to the extended forecast. It appears the
weather will be more active next week but timing is difficult to
pin down though the highest confidence in some rain chances appear
to be Monday.


VFR conditions throughout the TAF period.

Pressure ridge building across the area and air mass dry. Clear
sky. Winds northwest to northeast 5 to 10 knots.

Another cold front may bring precipitation and associated
restrictions Sunday into Monday




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