Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 202331
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
731 PM EDT Wed Sep 20 2017

.SYNOPSIS...
Surface high pressure will remain in the region during the rest
of the week. Upper troughing will be over the area through
Friday, which should help support scattered thunderstorms. Upper
ridging will begin to push back into the area Saturday and help
diminish the thunderstorm chance.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
An upper trough will remain over the Southeastern US through
tonight, with weak high pressure ridging into the forecast area
at the surface. Evening showers have all but dissipated with
sunset, and expecting dry conditions the remainder of the night.
Mostly clear skies, light winds, and some low-level moisture
may allow for some patchy fog formation late and towards sunrise
across the area. Overnight lows in the middle to upper 60s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
The models display surface ridging continuing in the region.
Aloft, troughing is depicted with h5 temperatures -9 to -10 C.
Instability associated with the upper feature combined with
strong surface heating should help support thunderstorms, but
expect little coverage because of shallow moisture and lack of a
well defined surface convergence feature. The guidance consensus
supports pops around 20 percent. Expect moderate instability.
The NAM has surface-based LI values -6 to -7. This instability
plus dry air in the mid levels aiding downdrafts could help
support strong wind with any thunderstorms. The temperature
guidance has been consistent with continued above normal values.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The GFS and ECMWF display surface ridging continuing in the region
through the medium-range period. Upper troughing is depicted
weakening or being suppressed farther southwestward. Most GFS and
ECMWF ensemble members indicate very low pops through the period.
The ensemble mean plus an average of the GFS and ECMWF MOS support
pops 20 percent or less. The guidance shows continued above normal
temperatures.

A weakness in the ridging north of Hurricane Maria plus upper
troughing over the Southeast States should steer the storm northward
and well east of the forecast area. The most reliable models have
been consistent with this solution. Please see the latest advisory
on Maria from the National Hurricane Center.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Previous isolated convection has dissipated. Fair skies
and light winds leads to some fog concerns.  Late afternoon
dewpoints were slightly higher than the previous day. However, some
upper level convective debris cloudiness from convection well to our
west introduces some uncertainties with regards to cloud cover
overnight. Guidance restricting fog to the fog prone sites AGS and
OGB.  After any morning fog, VFR expected Thursday. Only isolated
convection expected due to high LFC heights and limited atmospheric
moisture. Chances of SH/TSRA affecting the TAF sites appears too
small to include mention in the TAFs at this time.

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

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.

&&

$$



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