Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 262321
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
521 PM CST Wed Nov 26 2014

.UPDATE...
Issued at 520 PM CST WED NOV 26 2014

Updated for aviation forecast discussion.

&&

.SHORT TERM...(Tonight through Friday)
Issued at 300 PM CST WED NOV 26 2014

Main concern is the potential for light wintry precipitation through
the evening as a clipper system makes passage. Latest radar time
lapse indicates light precipitation covering the middle of the
forecast area. The precipitation started out as a mix of light rain
and light snow over southeast Missouri this morning. However, as
temperatures warmed, most of the precipitation has changed over to
rain this afternoon. That said, some snow flakes likely remain mixed
in across northern portions of southern Illinois.

As we progress through the late afternoon and evening, more of the
rain is forecast to become mixed with and transition over to light
snow as colder air filters in from the northwest. Snow accumulation
should remain on the light side - generally less than a half inch -
across southwest Indiana, northwest Kentucky, and southern Illinois
along and north of the Shawnee Hills. Any accumulation should be
most prominent on grassy and elevated surfaces. Lingering snow
will taper off west to east later this evening and overnight.

Behind the departing system, high pressure will build in for
Thanksgiving and Black Friday. While plenty of low clouds will be
around Thanksgiving morning, a trend towards more sunshine is
expected during the afternoon and especially Friday. Thanksgiving
Day will be quite cold as temperatures start off in the upper 20s
and lower 30s and only reach afternoon highs in the mid to upper
30s. Lows in the 20s Thursday night will be followed by milder
readings in the mid to upper 40s on Friday.

.LONG TERM...(Friday night through Wednesday)
Issued at 300 PM CST WED NOV 26 2014

Forecast confidence better in the first few 12 hour blocks of the
long term period, then drops off due to model differences through
the remainder of the period. Even so, there are a number of
precipitation possibilities during the period, all of them being of
the liquid variety.

The long term period starts off with high pressure at the surface
and west northwest flow aloft. On Saturday southerly winds will
moisten up the lower levels (AOB 700MB) and there will be decent
upglide on the I295 isentropic surface, so there might be patches of
sprinkles or drizzle over all but the far western and northwestern
sections.

Precipitation chances increase slightly Saturday night with
deepening moisture and the approach of a frontal system from the
northwest. A slight increase in POPS expected on Sunday as the front
draws even closer. Model timing on this feature not good. At 6 PM
Sunday the GFS has the front bisecting our CWA from NE-SW while the
ECMWF has it barely entering the western portions. Either way the
proximity of the boundary should generate an increase in POPS.

Sunday night both the GFS and the ECMWF generate a NE-SW band of
post-frontal precipitation, but due to placement of the boundary,
the bands of QPF differ as well. The GFS shows the best chances over
the southeast two thirds of the CWA, especially along and near the
KY/TN border whereas the ECMWF focuses the best chances over the
northwest two thirds of the area.

Precipitation chances should continue into Monday as a short wave
approaching from the southern plains induces a wave on the boundary
to our south thereby producing overrunning precipitation over the
area. Placement of QPF once again differs between models. Depending
on how much QPF there is over the northwest sections Monday
afternoon and how quickly the colder air filters in, a little snow
could be mixed with the rain in that area, but will leave all liquid
for the time being.

Monday night the flow aloft will veer around to the northwest enough
to push the aforementioned boundary and moisture out of all but the
far southeast sections of our CWA. Right now it appears Tuesday will
be dry although there could be small chances near the far southeast
corner of our CWA, but will keep dry for now.

From Tuesday night through the end of the period long term models
couldn`t be more different. Tuesday night the GFS brings an E-W
frontal boundary southward toward our region, keeps the boundary to
our north, then moves it back to the north as a warm front as a
strong storm system prepares to eject northeast out of the plains on
Wednesday. To be honest, at this point it`s difficult determining
what the ECMWF is thinking. It indicates a dry frontal passage
Tuesday night with surface high pressure overspreading the region on
Wednesday. For the sake of continuity and collaboration, will follow
Superblend output fairly closely which indicates precipitation
chances over all or part of our CWA both Tuesday night and Wednesday.

&&

.AVIATION...
Issued at 520 PM CST WED NOV 26 2014

Band of rain/snow moving through the area. Any additional activity
at KCGI/KPAH should be tapering off but lingering rain/snow could
continue for a few more hours. At KEVV/KOWB, precipitation is
knocking at the door and will start out as rain but quickly
transition to RASN to eventually all snow. Visibilities and cigs
will come down to MVFR. The precipitation will likely last several
hours and come to an end close to midnight or so. MVFR conditions
will linger overnight into Thanksgiving morning. Winds will become
northwesterly by tonight and into tomorrow as the low departs. We
should start seeing a break in the ceilings during the afternoon
hours.

&&

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

$$

UPDATE...CW
SHORT TERM...RJP
LONG TERM...JP
AVIATION...RJP/CW






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