000
FXUS63 KILX 091639
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1039 AM CST Mon Dec 9 2013

.DISCUSSION...
ISSUED 1039 AM CST Mon Dec 9 2013

1033mb high pressure centered over Kansas is providing cold and
dry conditions to central Illinois this morning. Low clouds
associated with departing storm system are still hanging on across
the E/SE KILX CWA, but have partially cleared the western half of
the area. Despite the loss of the low clouds, additional mid/high
clouds are already streaming northeastward into the area ahead of
a vigorous short-wave trough currently evident on water vapor
imagery over Arizona/New Mexico. As this feature approaches and
enhances lift within the right entrance region of a powerful 180kt
300mb jet streak across the southern Great Lakes, clouds will
continue to increase/thicken as the day progresses. 12z models are
in excellent agreement that a period of light snow will eventually
develop along/south of I-70 later this evening as the wave tracks
through the area. Current forecast through this afternoon is in
good shape, so no zone update is needed at this time.

Barnes
&&

.AVIATION...
ISSUED 543 AM CST Mon Dec 9 2013

Remaining MVFR cigs and any associated flurries will be scoured out
across the central Illinois terminals, on breezy westerly winds,
within the next few hours. Once the low clouds depart, VFR
conditions are expected for the remainder of the 12Z TAF valid
time. Additional cigs will spread into the area later today and
tonight as a disturbance tracks near the area, but they should
remain well into the VFR category.

Bak
&&

.PREV DISCUSSION...
ISSUED 225 AM CST Mon Dec 9 2013

Much of the earlier light snow and freezing drizzle has exited the
forecast area, with some patches of flurries continuing. Clearing
line just starting to edge into the far northwest CWA as of 2 am.
The low clouds have helped keep temperatures up in the 20s, but
teens will start moving into the northwest shortly as skies start
to clear.

Main concerns with the forecast involve timing of periodic, fast-
moving systems and associated precipitation chances.

SHORT TERM...Today through Wednesday:

An upper wave, currently entering the Texas/Oklahoma panhandles,
will zip northeast as a second, but stronger, trough swings
eastward from the Dakotas across the upper Mississippi Valley.
Main energy in our area will be with the southern wave, with a
narrow axis of light snow associated with enhanced lift in this
system. Have increased PoP`s after midnight to around 40% south
of I-70, where a couple tenths of snow are possible, but the
precipitation should be out of the area by sunrise.

Next in the parade of shortwaves expected to race through the
Great Lakes on Wednesday. Most forcing and moisture will remain
just to our north, but have added some 30% PoP`s for Wednesday
morning across the north.

Wind chills across the northwest late tonight should be getting
rather close to advisory criteria, with values of around 10 below
near Galesburg.

LONG TERM...Thursday through Sunday:

Upper pattern still looking to shift enough later this week to
keep the coldest air further to our north, with more of a split
jet stream setting up Thursday night. An initial weak cutoff low
in the southern stream will weaken to a trough as it ejects
eastward late Thursday night, reaching the mid-Mississippi Valley
late Friday night or early Saturday. May see some light
precipitation edging into the far southwest CWA late Friday
afternoon, but bulk of the precip will be Friday night into the
first part of Saturday. Concern will be amount of warmer air
available with this system. Latest GFS soundings showing a
freezing rain and sleet mixture Friday night over most of the CWA
before trending more toward snow, but the cooler ECMWF keeps the
precip mostly as snow. At this point, will not get too cute and
will just mention the snow, except for rain or snow across the
southeast on Saturday. Too many question with the pattern setup,
especially given that the ECMWF sends another slug of Arctic air
into the Midwest late in the weekend while the GFS keeps it much
warmer.

Geelhart

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$