Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 132012
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
312 PM CDT Wed Sep 13 2017

.SHORT TERM...(Tonight through Friday night)
Issued at 114 PM CDT Wed Sep 13 2017

Visible satellite imagery and radar mosaic shows cyclonic flow
persistent with Irma`s remnants lingering high rh/clouds/some pcpn
across PAH FA this pm. We do see some clearing just to the west of
the FA, but believe this will be slow to work across the region.

The gridded time/height cross sections reveal sub 700 mb moisture
remains high thru tmrw. Condensation pressure deficit values
remain below 30 mb thru tmrw as well. Where it does clear late
tonight, it should cloud in/fog up, with sub boundary layer moisture
still remaining high. Light rain may linger in the east thru the
evening hours, or until the weak wave of Low pressure at the
surface can depart and drag a little of the drier relative air
aloft into the lower Ohio river valley/points eastward.

As a result, we`ll be slow to clear...with expectation for
reformation of clouds diurnally tmrw, even with sunshine breaking
through. Gridded cpd`s increase to 100 mb or better tmrw after
sunset, so we`ll go for best clearing then. Height recovery/temp
recovery/on turnaround to southerlies commences then, esp Friday.

.LONG TERM...(Saturday through Tuesday)
Issued at 312 PM CDT Wed Sep 13 2017

As shortwave energy moves through the longwave trof in the western
CONUS, the PAH forecast area will be mainly under the influence of
persistent ridging. One impulse is shown by the medium range models
to move into south central Canada and induce a surface low/trof to
its east-southeast by Sun evening. This low will be attended by a
weak trailing cold front that should approach, but not necessarily
enter, the PAH forecast area. The low level boundary, and vorticity
associated with the parent impulse, may result in enough moisture
convergence and lift for isolated to scattered showers and a few
tstms. These could form across most of the region (especially the
northern half), mainly after midnight Sunday, through Mon afternoon.

In some model solutions, another mid level impulse appeared in the
western Gulf, traveling toward the MS River valley. This feature may
generate pcpn mainly west of the MS River by Tue in the form of
scattered showers and tstms. By Day 7 (Wed), the crystal ball is a
bit more murky, as there could be some breakdown of the ridging over
us (but not necessarily the upper Midwest). For now, PoPs for
measurable pcpn are very limited in our forecast, but could change.

Surface winds should generally remain out of the south for the
entire extended forecast. Expect temps to be on the warm side with
moderate humidity.

&&

.AVIATION...
Issued at 114 PM CDT Wed Sep 13 2017

Gridded time/height cross sections suggest high moisture in sub
700 mb layer, with condensation pressure deficit values remaining
at or below 30 mb, will linger low clouds. Any clear out late
tonight should be conducive for low cloud/fog formation, most
likely west (KCGI). Tmrw should see breaks as drier air in column
works further downward, but anticipate reformation of clouds/cigs
with ribbon of high mrh lingering in boundary layer where cpd`s
still pool less than 30 mb.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.

&&

$$
LONG TERM...DB



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