Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 101639
Area Forecast Discussion
National Weather Service Lincoln IL
1039 AM CST Tue Dec 10 2013
ISSUED 1039 AM CST Tue Dec 10 2013
Morning surface analysis shows low pressure over northern
Wisconsin, with cold front trailing southwestward into Iowa.
Ahead of the front, W/SW winds have brought slightly warmer air
into central Illinois. After overnight lows in the single digits
below zero in some areas, 16z/10am temps have rebounded into the
lower 20s. The exception is across the far southeast where a
substantial snow cover exists and current readings are hovering in
the teens at both Olney and Lawrenceville. Cold front will swing
through the region this afternoon, but not before high temps reach
the middle to upper 20s. Have made adjustments to hourly
temps/dewpoints and nudged highs up a degree or two accordingly.
Changes are minor and do not require a zone update at this time.
ISSUED 557 AM CST Tue Dec 10 2013
A clipper system will impact the central Illinois terminals today.
However, the effects will be limited to VFR cigs and gusty winds
as it passes through. While a break in the clouds is expected
behind this lead clipper, clouds will thicken again tonight as
another clipper approaches. It is not out of the question that
KPIA and/or KBMI may see some light snow by the end of the 12Z TAF
valid time associated with the second clipper, but will not
mention for now as bulk of the precipitation is expected to stay
north of the area.
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
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