Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 230248

Area Forecast Discussion
National Weather Service Columbia SC
1048 PM EDT Sun Oct 22 2017

A cold front will bring a chance of showers and thunderstorms
late tonight through early Tuesday, followed by cooler
temperatures for mid week. Fair with a warming trend late week.
Next weather system may approach by next weekend.


Radar showing more widespread showers developing within enhanced
isentropic lift over the Low Country pushing northwestward into
the Midlands and CSRA late this evening. Updated pops to likely
through 05z-06z to account for these showers. It does appear the
better isentropic lift does shift into the Upstate and out of
our area later tonight for a brief period before more
significant forcing and moisture transport arrive in the morning
so there may be a break in the showers 06z-10z or so.

Dewpoints have really come up with near 70 degree dewpoints
across the central and southern part of the forecast area with
drier air still over the northern Midlands. Warm afternoon
highs and overcast skies tonight with continuing moisture
advection and high dewpoints will result in overnight lows well
above normal in the 60s to around 70 degrees.


A mid- level shortwave trough will move across the Southeast
Monday as it lifts northward and gets absorbed into the broad
upper level trough. Strong moisture advection and isentropic
lift will allow an area of showers to develop early Monday
morning. We expect these showers to move northward through the
morning in the southerly flow. Isentropic lift diminishes late
Monday morning and there may be a break in shower activity
before a cold front moves in during the afternoon.

Monday afternoon, a cold front will push into CSRA and move
eastward through the Midlands during the late afternoon or
evening. High confidence in most of the area getting some
rainfall out of the system. Short range ensembles and model
guidance suggests around one inch of rainfall over the area.
All showers will be east of the forecast area by Tuesday

Strong surface forcing along/near the front and strong
divergence aloft will allow thunderstorms to develop in the band
of convection. Strong 0-3 km shear, with values greater than 35
kts, poses a threat for severe weather. The limiting factor
will be surface based instability. Showers during the morning
and overcast skies will limit low-level destabilization.
However continued warm, moist advection into the region may be
enough to compensate for the weak diabatic heating. If the low
levels are able to destabilize then damaging wind gusts in
bowing lines of thunderstorms will be the main threat. Given the
moderate helicity and strong 0-1 km shear expected we also
cannot rule out a brief tornado.


An deep upper trough will dig into the Southeast through mid-
week. This will bring dry weather and below normal temperatures
into the area. The trough exits the region late in the week as
surface high pressure moves offshore. This will allow
temperatures to warm and moisture to return for the weekend.
Another cold front will approach the region near the end of the
long term bringing back chances for precipitation.


Mix of MVFR and VFR conditions to start the period with
conditions deteriorating toward daybreak as a cold front moves
into the area.

Scattered rain continues to move inland from the coast with the
greatest impacts currently at AGS/DNL/OGB and expect the lower
cigs to move into CAE/CUB over the next couple hours. With
additional moisture moving into the area overnight expect cigs
to lower through the early morning hours with all sites seeing
IFR at times by daybreak. With isentropic ascent over the area
scattered rain will continue through much of the overnight. Cold
front will cross the area during the late afternoon and evening
hours with some potential for thunderstorms. Confidence in
timing and coverage of thunder currently too low to include in
TAFS and have remained with rain showers.

EXTENDED AVIATION OUTLOOK...Widespread restrictions expected to
continue through Monday night as a cold front crosses the area.




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