Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 292139

437 PM CDT Mon Sep 29 2014

Under ridging aloft, drier air mixed down to the sfc this afternoon,
more than yesterday. This may reduce the intensity/coverage of any
overnight patchy fog, especially in the ern half of the region.
Therefore, we have downplayed the overnight fog forecast somewhat.
Also updated the aviation discussion.


.SHORT TERM...(Tonight through Wednesday night)
Issued at 310 PM CDT MON SEP 29 2014

The PAH forecast area will be under general mid level ridging and
a high sfc pressure/weak sfc pressure gradient scenario for the
next 2 1/2 days or so. Meanwhile, a weak sfc boundary, driven by a
departing Great Lakes upper level low, will flirt with our
northernmost tier of counties late Tue/early Wed, with only a
slight increase in cloud cover the only expected effect. By Wed
afternoon, low level return flow is forecast to re-establish
itself ahead of a robust frontal system approaching from the

However, the latest models indicate that pcpn in far nwrn parts of
our region will likely be delayed until after midnight Wed night at
the earliest. This will be due to initial mid level shrtwv energy
digging through the nrn Plains late Tue, than departing into Canada,
leaving swrly flow aloft in place. The main ewd push of energy will
be a full latitudinal shrtwv Wed night, which may result in a quick
ramp-up of PoPs for the wrn half of the region between 06Z and 12Z
Thu, but certainly after that.

Temps were peaking slightly above forecast values today, and
under a similar (weak) wind field and air mass, the same thing
should happen on Tue. The forecast was adjusted accordingly from
the blended model output. Patchy fog, some dense, is still
possible tonight around the region.

.LONG TERM...(Thursday through Monday)
Issued at 310 PM CDT MON SEP 29 2014

Fairly high confidence in the extended forecast period.

The period will begin with a significant short wave and associated
cold front ejecting eastward through the plains, reaching the MS
River Valley late Thu or Thu night. Timing is still a bit
questionable with the features, but most models are within 3-6 hours
of each other. Also, still is some question as to whether the mid
level short wave can attain a bit of a negative tilt before reaching
our area, but forcing and moisture look more than sufficient to
support squall line development to our west Thursday. This line of
convection should translate east into our forecast area Thursday
night. The degree of shear and leftover instability will likely
determine how strong and storms become, but the possibility of some
type of convective watch box cannot be ruled out. Worth keeping an
eye on though. Higher PWATS pooling ahead of the system may also
contribute to a potential for some locally heavy rainfall.

Cold front will pass through the region by sunrise Friday, and usher
much cooler and drier air in for the Friday through Sunday time
frame. Could be quite chilly at night over the weekend, with many
areas well down into the 40s both mornings. Would not be surprised
if most locations get no higher that the 60s Saturday, or if we end
up with some 30s Saturday night up along the I-64 corridor.


Issued at 437 PM CDT MON SEP 29 2014

The primary challenge for the TAFs is vsby restrictions due to
patchy fog overnight, though the morning atmospheric column may be
drier than the previous morning, especially in the ern half of the
region, due to drier air mixing down to the sfc this afternoon.
Under the same air mass and light wind regime, it is still probable
that KCGI will fog in again with 1/2 to 1/4 vsby for at least
several hours, and LIFR cigs are still possible. Elsewhere, patchy
MVFR/IFR fog may occur, mainly in the general vicinity of bodies of
water. Vsbys should begin to improve noticeably by 1230Z-1300Z.




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