Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 252156

Area Forecast Discussion
National Weather Service Columbia SC
556 PM EDT SUN SEP 25 2016

An upper-level ridge will continue to build east across the region
tonight then move off the coast Monday. A cold front moving into
the area tonight will stall across the area Monday providing a
focus for scattered showers and thunderstorms. Another cold front
will cross the area Tuesday night into Wednesday. The air mass
behind this system will bring dry weather and more seasonable
temperatures for the latter half of the week.


A high amplitude upper-level ridge over the Mississippi Valley will
continue to move slowly east overnight. Upper-level cut-off low
over the Gulf coast area. At the surface, weak high pressure
remains. Upper-level trough over New England with surface ridge
building south along the Atlantic Seaboard will drive the cold
front slowly southwest tonight. The air mass across the region
will be marginally unstable. Convergence along the front and
upper-level dynamics appear weak. Latest high-resolution models
suggest little in the way of convection. Have forecasted slight
chance pops. Overnight lows generally in the upper 60s to around
70 degrees.


Easterly low-level flow Monday resulting in deeper moisture. A
stalled frontal boundary across the area will support scattered
showers and thunderstorms in a weakly to moderately unstable air
mass. Convection may focus near a sea breeze front in the east Monday.

Deep upper low along the US/Canadian border Monday is forecast to
move southeast into the Ohio River Valley by Wednesday. Thus will
push a cold front through our area late Tuesday into Wednesday.
We`re still seeing some timing differences with the 00Z ECMWF
holding the upper low and cold front farther west. The 12Z GFS AND
12Z NAM are more progressive moving the cold front to the coast by
the end of the day Wednesday. We have continued the chance for
convection ahead of the front Tuesday then diminishing from west
to east Wednesday as the cold front moves east of the Midlands.

Temperatures are expected to remain above normal ahead of the
front Monday and Tuesday, with highs in the mid to upper 80s and
lows in the mid 60s to lower 70s. Should see slightly cooler
temperatures Wednesday with highs in the low to mid 80s.


Typical fall weather to spread across the region for the end of
the week with seasonable temperatures.

Dry and cooler air advecting into the region Thursday. Surface
high pressure and stable conditions spreading across the region
into next weekend. Deep upper trough crossing the eastern states.
Overnight lows expected to range from the 50s to lower 60s with
afternoon highs in the mid 70s to lower 80s.


Weak convergence associated with a backdoor cold front moving
into the area will help support stratus and fog development
tonight. Most of the NAM and GFS MOS plus HRRR suggested mainly
IFR stratus. Followed the GFS LAMP for the timing. Continued upper
ridging should help keep moisture shallow. Nocturnal cooling
should limit instability. The shower and thunderstorm chance
overnight was too low to include in the terminal forecasts at
this time. The diffuse front will remain in the area though the
rest of the TAF period but some diurnal ceiling improvement
should occur. The GFS and NAM MOS were in good agreement with
generally VFR conditions developing during the day. Some increase
in moisture will occur in an easterly flow Monday. The moisture
and some convergence associated with the diffuse front in the area
plus heating should support scattered showers and thunderstorms
but still expect limited coverage with significant forcing
associated with the next approaching cold front west of the area
through the TAF period. Again, the shower and thunderstorm chance
was too low to include in the terminal forecasts at this time.

EXTENDED AVIATION OUTLOOK...A slow moving cold front will be in
the area through Wednesday. Widespread stratus and fog may occur
especially during and late night and early morning hours. There
will also be scattered showers and thunderstorms. Drying may occur
behind the front Thursday.




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