Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 140550
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1150 PM CST Wed Dec 13 2017

.UPDATE...
Updated aviation section for 06z taf issuance

&&

.SHORT TERM...(Tonight through Friday night)
Issued at 300 PM CST Wed Dec 13 2017

Latest short term guidance is not as robust with the winds late
this afternoon, so the 4 PM expiration of the Wind Advisory should
be ok. A few spots exceeded 40 mph, but much of the area has
fallen just short. The mixing apparently was not quite
deep or strong enough to tap the stronger winds over a broad area
and that is likely what held temperatures below forecast levels.
On the bright side this helped keep the fire danger in check.

The clipper system will pass safely by to our northeast keeping
any precipitation well out of our region. The associated cold
front is not very sharp, but winds will continue to veer to
northwest through the evening while gradually diminishing.

Behind this disturbance the flow aloft will gradually become zonal
Thursday, as surface high pressure settles over the region. A
broader and weaker upper-level trough will move through the region
Thursday night and Friday, but there will be no moisture for it to
work with, so our area will remain dry.

There is quite a bit of uncertainty in the cloud forecast tonight
through Thursday night, so temperatures will be tricky. Did not
stray from the consensus of guidance through the period. It will
feel quite a bit cooler Thursday, but that is as much due to
cloud cover as cold advection. With surface high pressure
lingering over the region Friday it will remain below normal, but
sunshine should allow for some warming relative to Thursday.

.LONG TERM...(Saturday through Wednesday)
Issued at 300 PM CST Wed Dec 13 2017

The latest runs of the medium range models were in decent agreement
depicting the rain event for the PAH forecast area late in the
weekend, perhaps differing by a few hours with the onset (early Sun)
and cessation of the pcpn (Sunday evening). Where they differed more
was with what may happen after that, because of different
positioning/evolution in the solutions of a second shortwave trof
swinging through the southwestern CONUS and eventually into our
region.

The models now all show a northern Mexico cut-off low pressure
system will eject northeastward early in the weekend and open,
producing the brief Sun rain event for us. The ECMWF, while not
phasing the two shortwaves anymore, does have the second shortwave
much farther north (Four Corners), and yet another upper low over
the eastern Pacific. The position of the Four Corners low in the
ECMWF solution will enable it to move through the PAH forecast area
on Mon, potentially resulting in showers. However, the current model
consensus suggests that Mon will be dry under west-southwesterly
flow aloft.

The GFS and CMC solutions were quite similar with the position of
the second shortwave as it moves eastward and opens Mon/Mon night,
with the exception of the deeper moisture and more coherent trof
depicted by the GFS. This had enough of an effect on the
initialization blend to have a limited chance of rain, mainly Tue
morning. This was left in the forecast for now, though the GFS has
been quite changeable.

Otherwise, as ridging aloft builds over the western CONUS by Day 7,
expect increasingly anti-cyclonic flow aloft across the nation`s
midsection and a ridge of high surface pressure in our vicinity.
This pattern change will be conducive to somewhat milder
temps/dewpoints/RHs in the extended forecast.

&&

.AVIATION...
Issued at 1150 PM CST Wed Dec 13 2017

A large area of low clouds has been dropping southward across
Missouri/Illinois/Indiana this evening. Bases are mainly vfr across
Missouri and western IL. However, mvfr cigs are prevalent across
Indiana and ern Illinois. The computer models have not been very
adept at picking up this cloudiness. The 06z forecast is more
pessimistic than the previous one, based on satellite and surface
obs. Cigs around 3k feet are forecast at all sites through the day
Thursday, with mvfr conditions at times in sw Indiana/nw Kentucky.
Low clouds should clear out around sunset.

Winds will be northwest around 10 kt, becoming north at 5 to 10 kt
on Thursday morning.

&&

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

&&

$$

SHORT TERM...DRS
LONG TERM...DB
AVIATION...MY



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