Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 222351

Area Forecast Discussion
National Weather Service Paducah KY
651 PM CDT Sun Oct 22 2017

Issued at 651 PM CDT Sun Oct 22 2017

The AVIATION section has been updated for the 00Z TAF issuance.


.SHORT TERM...(Tonight through Tuesday night)
Issued at 227 PM CDT Sun Oct 22 2017

Been a drier day than earlier expected. However, showers are
finally beginning to to break out along the MS River as an upper
low begins to wind up over southwest MO. The shower activity is
expected to continue to develop late this afternoon and early
tonight and spread east across the rest of the forecast area. In
fact, the easter part of the forecast area will likely see the
highest rain totals, possibly upwards of 2 inches over the
southern Pennyrile of western KY, where better upper level
diffluence/upward motion will take place. Rain amounts should
drop as one heads west toward the MS River, with only a quarter
inch or less expected over southeast MO. The 12z operational GFS
still is quickest in shifting the precip east of the region early
in the day Monday, but most of the significant precip should shift
east of the region by that time, with only left over wrap around
showers in portions of western Ky and sw IN.

Skies should temporarily clear out from west to east during the
day Monday as the upper low opens up and lifts northeast around
the base of a larger trof to its northwest. However, that larger
upper trof is expected to dig south into the lower Great lakes
region by Tuesday accompanied by a secondary cold front. This
will bring another round of clouds, especially to climatologically
favored regions of our north/east. This system will also bring a
decent shot of chilly fall air south out of Canada. Max temps on
Tuesday will likely stay in the mid/upper 50s at most locations.
Expect lows down in the 30s Tuesday night with some scattered
frost not out of the question.

.LONG TERM...(Wednesday through Sunday)
Issued at 227 PM CDT Sun Oct 22 2017

A deep 500 mb longwave trough will stay over eastern North America
through the long term period. This will result in very cool
northwest flow most of the time. A strong cold front will bring a
chance of showers late in the workweek.

As far as the details, the 12z model runs have come into better
agreement on the timing of specific features. In particular, they
agree on the timing of the strong cold front. Based on these 12z
runs, precip chances will increase on Friday as the cold front
passes southeast across the Lower Ohio Valley. Next weekend should
be mainly dry based on the latest models. Pops have been lowered to
slight chance for Saturday and Saturday night, and they will likely
be removed in later forecasts if the models continue to trend drier.

The other forecast issue is temps. On Wednesday, the models continue
to show a sharp 850 mb temp gradient as the leading edge of warmer
air arrives on westerly winds aloft. There will also be considerably
more sun in the west, especially se Missouri. Therefore, highs may
range from the lower 50s in sw Indiana to the mid 60s in the Ozark

Wednesday night and Thursday will be the mildest period of the long-
term. Southwest flow ahead of the cold front will boost 850 mb temps
into the teens on Thursday. This should translate into highs around
70 in many areas, except mid 60s in the Evansville tri-state area.

Behind the cold front, temps next weekend will be chilly. There are
rather large model differences in 850 mb temps, ranging from minus 8
on the colder gfs to around 0 in the ecmwf. The forecast will keep
highs in the 50s both days. However, if clouds are stubborn to leave
Saturday or if the colder gfs is correct, highs would be in the 40s.
A widespread frost or freeze is possible Sat night as well.


Issued at 651 PM CDT Sun Oct 22 2017

The cold front will reach KPAH near the beginning of the period,
but it may take most of the evening to reach KEVV and KOWB as an
upper low develops over Arkansas. Showers and possibly a
thunderstorm or two will stream north through KPAH for the first
half of the evening and then slowly push eastward in the late
evening and into the overnight hours. There are some tiny heavier
elements just west of KPAH, and those may produce a few lightning
strikes, so decided to insert VCTS with the primary band of
heavier showers.

There may be a healthy gust with the cold frontal wind shift to
the northwest, but that should not last long. Behind the main band
of showers, IFR ceilings with MVFR drizzle are forecast overnight
into the morning hours. Ceilings should lift in the morning as
the deformation zone passes and produces a few more bonafide
showers. Abrupt clearing is likely from west to east through the




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