Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 191259

Area Forecast Discussion
National Weather Service Columbia SC
859 AM EDT Tue Sep 19 2017

Surface high pressure will prevail across the region today
providing dry and unseasonably warm weather. Upper troughing
will be over the region Wednesday through Friday, which should
help support isolated to scattered thunderstorms. High pressure
will restrengthen on Saturday and dry conditions are expected
over the weekend.


Upper ridging will continue over the Southeastern states today
and will retreat south of the area tonight. High pressure will
continue ridging into the forecast area at the surface.
Scattered cumulus will develop again this afternoon, but
moisture will be limited and a mid- level capping inversion
should keep showers from forming. It will be another warm day
with highs in the upper 80s.


An upper level trough will move into the forecast area on
Wednesday with h5 temperatures lowering to -9C to -11C. Cooling
aloft combined with strong surface heating and convergence into
a lee-side trough should help support thunderstorms. Convection
coverage should be limited by shallow moisture with surface
ridging continuing west and south of the area. Have indicated
pops around 20 percent on Wednesday. Both the NAM and GFS
indicated moderate instability with surface-based LI values
-5C to -8C. Strong wind gusts may occur with any thunderstorms
 given steep lapse rates and inverted V soundings.

Above normal temperatures are forecast with highs in the upper
80s and lower 90s...with nighttime lows in the mid 60s to around
70 degrees.


The GFS and ECMWF display surface ridging beginning to ridge
into the forecast area from the north Thursday with this ridging
continuing through Monday. Upper troughing is depicted
weakening or being suppressed farther southwestward. Most GFS
and ECMWF ensemble members indicate low pops through the period
but with the highest values Thursday and Friday likely
associated with lingering upper troughing. The ensemble mean
supports pops 20 to 30 percent Thursday and Friday, and less
than 20 percent Saturday through Monday. Hurricane Maria will
likely be off the Southeast Coast early next week. See the
latest advisory on Maria from the National Hurricane Center.

Afternoon highs will be above normal Thursday and Friday...then
near normal readings over the weekend.


VFR conditions expected outside of possible early morning fog

Upper ridging over the Southeast combined with weak surface
high pressure over the area will promote dry and warm weather
today. Scattered cumulus will develop by early afternoon. Cloud
cover and increasing low-level flow may limit fog development
on Wednesday morning.

EXTENDED AVIATION OUTLOOK...Late night/early morning
fog/stratus possible each morning, mainly at AGS and OGB.
Scattered diurnal convection possible Thursday and Friday.




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