367
FXUS63 KILX 031752
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1152 AM CST Wed Dec 3 2025

.KEY MESSAGES...

- Widespread flurries and patchy freezing drizzle begins early
  this afternoon. Only limited travel impacts are anticipated, but
  there could be a few slick spots wherever wintry precip becomes
  focused. Drive with caution, especially during the afternoon and
  evening commute.

- The coldest air of the season so far will arrive tonight and
  last through Friday morning. Take immediate steps to protect
  people, pets, and pipes from the cold.

&&

.UPDATE...
Issued at 1032 AM CST Wed Dec 3 2025

Skies are cloudier than expected and lots of very low clouds are
advecting into the CWA from the south. The thicker cloud cover
will hold temps back this afternoon, so will be lowering daytime
highs a couple of degrees over most of the area. Cold front is
still expected to move through the area from the northwest. A
narrow ribbon of lift is still being forecasted along the front,
so precip is possible along the front today through tonight. Radar
returns show precip should be occurring across parts of IL.
However, most of the returns over the CWA are not reaching the
ground at this time. As moisture increases below the cloud layer,
precip will begin to occur at the surface. Based on forecast
soundings, most of the precip will be snow. However, forecast
soundings show us loosing cloud ice behind the front. So, believe
some FZDZ is possible along and behind the front in areas where
very low clouds and lower visibilities are present. Already have
some isolated spots of FZDZ and FZRA (15-25%) in the grids and see
no reason to change that at this time.

Remainder of forecast for this afternoon into this evening looks
fine. Updated grids/forecast have already been sent.

Auten

&&

.DISCUSSION...
Issued at 239 AM CST Wed Dec 3 2025

A good surge of warm air advection is currently underway early
this morning. This is due to surface winds shifting southerly as
surface high pressure departs. As a result, temperatures are
expected to slowly climb into the lower 30s this afternoon, ahead
of an approaching cold front.

A decent signal persists for wintry precipitation to develop
behind the front by early afternoon. This is linked to a
sharpening 700 mb Frontogenetic (FGEN) band beneath a pair of
phasing jet streaks aloft. The latest HREF guidance places the
greatest chance (30-50%) for PoPs along the I-70 corridor around
00z, where wet-bulb temperatures are cold enough to support snow.

The main challenge is a particularly non-uniform vertical
moisture profile, with cloud ice present in some areas but absent
in others. This creates a precipitation type (p-type) challenge,
making both snow showers and freezing drizzle plausible. HREF QPF
LPMM still suggests a range of a trace to 0.10 inches, with the
higher end most likely where the FGEN band develops, and the lower
end elsewhere.

In total, this points to widespread flurries and patchy freezing
drizzle, with the potential for a narrow stripe of light
accumulating snow. Our base case forecast calls for a skift of
wintry precipitation in most areas, but up to one inch of new snow
accumulation is possible (10% chance) along or near the I-70
corridor this evening.

The region then braces for the coldest air of the season so far,
arriving behind the arctic front and lasting from tonight through
Friday morning. This exceptionally cold spell for early December
will bring temperatures about 25-30 degrees below average.
Overnight lows will plummet to the single digits, and daytime
highs will struggle to reach the 20 degF, especially north of
I-70. Additionally, wind chill values in our northern areas are
expected to approach advisory criteria both tonight and Wednesday
night.

Marginally warmer and continued dry weather is expected by the
end of the week, as the storm system previously of concern for
Friday remains forecast to pass to the south. However, a signal
for light accumulating snow returns this weekend. This is
attributed to a clipper-like system moving across the Corn Belt,
driven by a choppy northwest flow. The latest guidance from the
NBM and Grand Ensemble (GEFS, GEPS and EPS) currently gives a low
(less than 20%) chance for at least one inch of snow, though this
probability may be understated due to existing differences in
timing among the models.

The extended forecast hints at a substantial warm-up by the
middle of next week. This is due to a longwave ridge settling over
the western US, which will bring warm, downslope flow across the
Plains, eventually advecting into the Midwest. During this period,
a series of clipper systems are expected to track across the
Upper Mississippi Valley into the Great Lakes, potentially grazing
our northern forecast areas at times.

MJA

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1152 AM CST Wed Dec 3 2025

IFR cigs are already ongoing at DEC, BMI, and CMI, but as the
front moves into the area from the northwest, IFR cigs are
expectedat SPI and PIA. All sites will see IFR cigs/conditions
as the front moves through the area with -sn. Forecast soundings
from various models indicate that some -FZDZ is possible as well,
so this is included in the PROB30 groups at all sites late this
afternoon into this evening. MVFR clouds will return after the
precip and front moves through. Then question is will VFR
conditions return overnight. Thinking lower clouds will dissipate
around midnight at PIA and then move to the southeast through the
overnight hours. Winds will be southwest ahead of the front and
then become northwest as the front moves through. North-northwest
winds are expected this evening into overnight and tomorrow. Wind
speeds will be breezy with gusts over 20kts ahead of the front and
then become lighter as the front moves through, then breezy again
during the evening hours, then become lighter again overnight.

Auten

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$