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000
FXUS63 KILX 100849
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
249 AM CST Tue Dec 10 2013

.DISCUSSION...
ISSUED 247 AM CST Tue Dec 10 2013

Fast moving area of light snow, along axis of 170+ knot jet at 300
mb, is slowly shifting southward but is persisting in the extreme
southeast corner of the forecast area. An area of clearing has
pushed through a good portion of the CWA northwest of I-70, and
temperatures have been dipping below zero northwest of the
Illinois River. Clouds are already quickly moving east through
Iowa, associated with the next shortwave that is currently diving
southeast through Minnesota.

Several waves/storm systems to focus on over the next several
days, with the Friday night system of most concern for widespread
wintry weather over the forecast area.


SHORT TERM...Today through Thursday:

Incoming wave this morning will only provide us with a glancing
blow of the mid/high clouds, however rather blustery conditions
can be expected. Next wave of concern is currently dropping into
western Montana, with and will rapidly track southeast. Latest
models continue to produce light snow from northern Iowa into
northern Illinois overnight, exiting the area Wednesday morning.
Main snow axis expected to be just north of us toward the I-80
corridor, but a half to 1 inch of snow is plausible across the
extreme northern CWA from Galesburg to Minonk. Temperatures only
expected to reach the mid to upper 20s today, but hold fairly
steady in the teens overnight.

Next surge of Arctic air poised to drop southward through the
Great Lakes on Wednesday, as the snow exits. Will go with falling
temperatures over most of the CWA Wednesday afternoon. Lows
expected to drop into the zero to 5 above range Wednesday night,
with wind chills below zero in most areas. This shot of cold air
will be brief though, with some slow moderation beginning on
Thursday.


LONG TERM...Friday through Monday:

Forecast starts to become more complicated toward the end of the
week, as the split upper flow tries to phase a bit and develops a
significant trough across the middle of the country. Longer range
models coming into better agreement with timing of precipitation
and surface features that will affect our area later Friday into
early Saturday, but are still struggling a bit with the precip
type. Some indications of a bit of sleet or rain possible Friday
afternoon, primarily across the southeast, before changing back
over to snow. Currently looking like a couple inches of snow will
be possible, especially southeast of I-55 where heavier precip
will track northeast ahead of the main wave. Snow will taper from
west to east on Saturday.

Later in the weekend, the models are in reasonable agreement with
dropping a closed low into the upper Great Lakes region, with an
associated surge of Arctic air. However, they have a rather wide
spread on exactly how intense and far south this air mass will
reach, with 850 mb temperatures over us ranging from -3C on the
ECMWF model, to -18C on the GFS and -28C with the Canadian model.
The latter model would suggest highs well below zero. Temperature
grids will trend more toward the ECMWF, suggesting mainly 20s over
the area.

Geelhart

&&

.AVIATION...
ISSUED 1154 PM CST Mon Dec 9 2013

VFR conditions will continue through this TAF period. The main
clouds of note will be mid and high clouds associated with a
weather disturbance moving rapidly across southern and SE IL the
rest of the night. Light snow will accumulate south of I-70,
especially toward Lawrenceville. No snow is expected at any of the
terminal sites the rest of the night, as confirmed by radar
trends.

Winds will begin to shift from northwest at the start of the TAF
period to southwest by sunrise. Wind speeds will rapidly increase
from the southwest Tuesday morning, with sustained speeds in the
14-17kt range, and gusts to 25-27kt. Those winds will be driven by
a fast moving clipper passing across far N IL. The winds will
diminish Tues evening as the pressure gradient weakens.

The next clipper will quickly approach NW IL toward the end of
this TAF period 06z Tues night, but any snowfall should hold off
until after midnight.

Shimon
&&

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

$$