Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 021147
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
547 AM CST Fri Dec 2 2016

.UPDATE...
Issued at 547 AM CST Fri Dec 2 2016

Updated aviation section.

&&

.SHORT TERM...(Today through Sunday night)
Issued at 315 AM CST Fri Dec 2 2016

General high surface pressure and slight ridging aloft will keep
conditions dry for most of the PAH forecast area through the
daylight hours Saturday, though clouds will be on the increase
from southwest to northeast even before daybreak. The only
exception to the rain free conditions is southern parts of
southeastern MO where measurable rain may reach the ground by
afternoon. Dewpoints in the lower 30s represent the dry air in the
lower trop that will have to be overcome by the falling pcpn.

Increasing moisture ahead of two systems should combine Saturday
night. Lift from shortwave energy coming out of the central
Plains will make pcpn more certain for us, though areas to the
north of I-64 will be the last to receive it. Atmospheric profiles
are conducive to some ice nucleation occurring in roughly the
northern two-thirds of the region after midnight Saturday and for
a time after sunrise Sunday morning. Surface temps in the lower to
middle 30s there should allow snowflakes to survive to the ground,
but with warm ground conditions, impacts to travelers are not
expected. Pcpn amounts are expected to be light with this event,
which will end abruptly Sunday afternoon as the shortwave moves
eastward.

Highs Sunday will be even cooler (mid 40s) than Saturday, mostly
due to evaporative cooling processes.

.LONG TERM...(Monday through Thursday)
Issued at 315 AM CST Fri Dec 2 2016

Model preference at the beginning of the period continues to weight
toward slower solutions, with the focus on energy over the southern
Plains ejecting NE toward the area Monday night. So slightly greater
weight given to the GFS vs. the EC, though the new EC is more in
line. The direct affect will be on how quickly rains spread NE
across the area. Will continue with an increasing afternoon PoP for
rain, lowest I-64 by dark to mid chance toward the TN/AR borders 18z-
00z. Additional timing aspects are tied to the models lowering
condensation pdef values required for saturation, with increasing
I300K isentropic lift. Categorical PoPs Monday night, tapering off
in the east Tuesday morning with the passage of the upper level
energy. Will keep a limited thunder mention across west KY Monday
night, though it may not happen (barely sufficient elevated
instability).

Confidence decreases significantly with respect to the mid week
system Wednesday/Wednesday night. For now, dry Tue afternoon and
Tuesday night. After that, the GFS continues to be faster spreading
precip in Wednesday, and has it out of here by Wednesday night, save
for a glancing shot maybe along the I-64 corridor overnight.
Meanwhile the EC and its ensemble members continue to be slower, and
favored by WPC, with additional support seen at 144 hr via the CMC,
suggesting chances hold off til Wednesday afternoon, peaking
Wednesday night. The latest EKDMOS, and EC temp guidance is not as
cold either for Wednesday night. There is a high level of
uncertainty as to whether or not, 1) it will be cold enough for a
change over to some light snow before ending, and 2), if any
moisture will be left when the colder air arrives, should the
slightly faster solutions pan out. Therefore we will abandon the
inherited overly detailed wx blend grids (spatial and temporal), and
significantly wash out these specifics with just a R-/S-mention, in
the chance category. In the system`s wake, dry weather should
return for Thursday, along with colder temperatures.

&&

.AVIATION...
Issued at 547 AM CST Fri Dec 2 2016

High pressure over the lower Mississippi valley will migrate slowly
northeastward across the Tennessee River valley and toward the
Cumberland plateau over the next 24 hours. Winds under 10 knots will
veer through the period as a result, going calm or near calm at
night. A band of VFR clouds will continue over southeastern MO this
morning and eventually mix out. VFR cloudiness is forecast to
increase mainly west of the MS River by Saturday morning. Aside some
MVFR vsbys in fog in parts of southern IL this morning, vsbys will
be unlimited through the 24 hour TAF period.

&&

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

$$

SHORT TERM...DB
LONG TERM...CN
AVIATION...DB


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