Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 270949

349 AM CST Sat Dec 27 2014

.SHORT TERM...(Today through Monday)
Issued at 349 AM CST SAT DEC 27 2014

Medium confidence in the short term due to model differences where
POPS, QPF, and timing are concerned.

Deep southerly flow will saturate the lower troposphere this
morning. This combined with an approaching cold front, southwest
flow aloft with weak embedded ripples of energy, and becoming under
the right entrance region of a 120+ knot jet, expect rainfall to
overspread the region today.

The front is expected to cross our CWA this afternoon into this
evening, so rainfall chances should be highest area wide in this
time frame. Not expecting heavy rainfall or flooding with this
event, mainly just steady and soggy over the next 36 hours.

In the wake of the front late tonight, with the rest of the
atmospheric dynamics remaining nearly unchanged, rainfall still
a good bet across our CWA, especially the southeast half. There
could be a lull here and there, but too difficult to try and pin
down the timing.

Sunday precipitation chances will finally begin to decrease from the
northwest as the parent H5 trough weakens and moves eastward in
addition to a decrease in deeper moisture and loss of the upper jet
interaction. Before completely clearing the area, small
precipitation chances may linger over the southern Pennyrile region
of western Kentucky near the KY/TN border Sunday evening. Beyond
that high pressure at the surface and zonal flow aloft should keep
the region dry and a tad cooler.

.LONG TERM...(Monday night through Friday)
Issued at 349 AM CST SAT DEC 27 2014

A dry forecast is in store for most of the extended period. Sfc
pressures will continue to rise through mid week.

A developing split flow across the CONUS on Wed will be conducive to
an arctic air mass from the nrn stream sweeping into the PAH
forecast area. The initialization blend seemed to have a better idea
of what the dewpoint numbers will likely be at the sfc (single
digits Wed, teens Thu). By then the mid level flow will be slightly
cyclonic but confluent. This combined with the very dry air in the
low levels will tend to delay onset of measurable pcpn with the next
system to affect the area by the end of the week.

Med range model solutions begin to differ late in the extended
period, particularly with the evolution of the large swrn CONUS low
pressure system. Far to the east of the system, the 00Z ECMWF had
stronger mid level winds ahead of it than the 00Z GFS by 12 Fri,
thus expanded the warm advection pcpn much farther east (and over
the PAH forecast area). Due to some uncertainty, and in the interest
of collaboration with other offices, we kept the PoPs low chance to
slight across the region Thu night, and in the chance category Fri.
The forecast certainly looks wet or icy to some degree Fri night
(Day 7 night).

Temps and dewpoints should start to rebound by late Thu from Wed
highs near or below freezing, but not quite enough to preclude a
wintry mix of pcpn Thu night/Fri morning. Pcpn will probably change
over to rain nearly everywhere for Fri afternoon, then a wintry mix
might develop Fri night in the vicinity, and north of, I-64.


Issued at 349 AM CST SAT DEC 27 2014

Mainly light showers are already flirting with KCGI, so had to
speed up the onset eastward overnight. Otherwise, the general
trends and timing are similar to the previous forecast. Still
looking for ceilings dropping to IFR levels if not lower mainly in
the afternoon. The cold front is still expected to reach KCGI by
00Z and the other sites a few hours later. May see some
improvement in visibility behind the front, but IFR ceilings will
likely hang on through the end of the period with the possible
exception of KCGI. Still cannot rule out a rumble of thunder
mainly in the morning. IFR visibilities in rain/drizzle will be
possible Saturday.




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