Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 242348
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
648 PM CDT Sun Sep 24 2017

.UPDATE...
Issued at 648 PM CDT Sun Sep 24 2017

Updated aviation discussion for 00Z TAFs.

&&

.SHORT TERM...(Tonight through Tuesday night)
Issued at 153 PM CDT Sun Sep 24 2017

Widely scattered convection developed as expected across southeast
MO, southern IL along and south of route 13, and west KY this
afternoon. We had to readjust slight PoPs back north just a tad.
This activity will continue into the early evening then fade.
Should be last to end across southeast MO. Overnight, quiet
weather expected, with calm conditions and patchy fog developing
once again.

Monday, will leave the forecast dry for now. There may need to be
an inclusion eventually across SEMO. However moisture is less
adequate, with weaker support aloft. Will monitor. Monday night
through Tuesday night, dry weather as mid level heights rise
slightly. Relatively strong cold front may make its passage late
in the night (wind shift), with moisture lagging behind the front.

Will continue to follow MOS and persistence for temps. Leaned
toward the NAM in the near term, and a model blend for the
remainder of the short term.

.LONG TERM...(Wednesday through Sunday)
Issued at 153 PM CDT Sun Sep 24 2017

The hemispherical five wave pattern remains fairly stable over the
North American continent, with a well telegraphed evolution and
persistence of the western U.S. trough and the eastern U.S ridge
placement by medium range model guidance this past week.

Current and forecast height changes over the four corners region
indicate some slight filling of the closed low in this area through
Tuesday and a gradual translation of this low toward
Minnesota/western Great Lakes through Thursday.

With the exception of the 00z Thursday (7pm CDT Wednesday) through
18z Thursday ( 1 pm CDT Thursday), the mean 1000-500 mb layer
relative humidity (essentially deep layer moisture) does not rise
above 55% through 06z Saturday (1 am CDT Friday) for any of the 00z
Sunday medium range guidance, with most of the guidance remaining
below this threshold through 06z Sunday (1 am CDT Saturday).  This
general increase in moisture is associated with the
direct/indirection circulation and advection associated with the
cold frontal passage early on Wednesday. Without any focused lift
and duration of convection, any precipitation potential will be
insufficient to produce measurable amounts.

At this point, given recent numerical model trends, will keep the
extended forecast period dry. The prolonged period of subsidence
will continue to support lesser mixing, an lack of lithometeor
transport (dust, etc...), and an increase in haze and ground based
ozone/particulate concerns (air quality), temperatures will remain
at or above normal. Some reduction in temperatures and improvement
in air quality will occur with the frontal passage late Wednesday.

Forecast confidence continues to remain high for this weather
scenario.

&&

.AVIATION...
Issued at 648 PM CDT Sun Sep 24 2017

Generally VFR conditions are expected through Monday. Isolated
showers and storms will diminish early this evening, leaving behind
scattered mid to high clouds which will diminish through the night.
Some patchy late night fog is possible once again. Winds will remain
light.

&&

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

$$

Short Term...CN
Long Term....Smith
Aviation...RJP


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