113
FXUS63 KILX 021750
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1150 AM CST Tue Dec 2 2025

.KEY MESSAGES...

- The coldest air of the season will settle in Wednesday night
  through Thursday night. Wind chill values will approach advisory
  criteria near Interstate 74.

- A clipper system will push across the Corn Belt this weekend.
  There is currently a low (20-25%) chance that snowfall will
  exceed 1 inch.

&&

.DISCUSSION...
Issued at 329 AM CST Tue Dec 2 2025

A compact shortwave trough is currently lifting north through the
lower Ohio River Valley this morning, as indicated by mid-level
water vapor imagery. A drier, subsident air mass is settling in
behind this feature. Regional model soundings show a shallow pinch
of moisture trapped beneath a strong subsidence inversion, which
is causing low stratus and pockets of dense fog. The combination
of yesterdays snow accumulation and todays patchy freezing fog may
result in a continued slippery morning commute.

Afternoon temperatures are expected to remain close to morning
lows, as light winds beneath the stubborn subsidence inversion
limit mixing and keep skies mostly cloudy. Low clouds will persist
into this evening, with temperatures falling into the mid-teens
to around 20 degF across the region.

Overnight, a good surge of warm air advection is expected as
surface winds shift southerly behind departing surface high
pressure. This will cause temperatures to slowly climb into the
low-to-mid 30s Wednesday afternoon ahead of an approaching cold
front.

There remains a decent signal for scattered snow showers to
develop behind the front by early Wednesday afternoon. This is
associated with a sharpening band of shallow FGEN (925-850 mb)
beneath a pair of phasing jet streaks aloft. The latest 00z RRFS
guidance suggests a medium chance (30-50%) for PoPs north of I-72,
with the wet-bulb temperature cold enough to support snow. This
same guidance also supports a range of QPF from a trace to 0.10
inches. Consequently, our base case forecast is for a dusting to
one inch of new snow accumulation in areas north of I-72.

The region will experience the coldest air of the season so far
from Wednesday night through Friday morning. Overnight lows will
drop into the single digits, and daytime highs will only reach the
teens, particularly in areas north of I-70. These conditions are
exceptionally cold for early December, running approximately 25-30
degrees below average. Furthermore, wind chill values in our
northern areas are expected to approach advisory criteria.

Marginally warmer and continued dry weather will then stretch
through late week as the storm system for Friday that we were once
concerned about passes well to our south. Nevertheless, there is
an emerging signal for another shot of light accumulating snow
this weekend as choppy northwest flow brings a clipper-like system
across the Corn Belt. Latest guidance from the NBM and Grand
Ensemble (GEFS, GEPS and EPS) support a 1 in 4 chance for at least
1 inch, though this probability may be artificially low due to
some timing differences that still exist.

MJA

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1150 AM CST Tue Dec 2 2025

Low clouds continue to blanket central Illinois late this morning.
Most terminals have improved to low MVFR: however, both KBMI and
KCMI are hanging on to IFR. 1730z/1130am satellite imagery shows
the back edge of the overcast advancing eastward across Iowa/Missouri
to the Mississippi River. While satellite trends appear optimistic
for clearing across west-central Illinois this afternoon, both
NAM and HRRR forecast soundings suggest the clearing line will
slow substantially...and may not reach KPIA until around 02z...and
not to KCMI until perhaps 14z/15z Wed. Winds are presently light,
but will back to SW and increase tonight as a cold front approaches
from the northwest. Once the SW flow commences, the low clouds
will finally get shoved out of east-central Illinois by late morning
Wednesday. As WAA increases over the fresh snow cover, fog will
become a concern tonight...particularly east of the I-55 corridor.
CAMs are most aggressive with lowered visbys further east in
Indiana: however, based on what happened last night into this
morning, think fog will develop further west than the models
indicate. As a result, have lowered visbys to around 4 miles at
KDEC and 2 miles at KCMI between 09z and 13z. Once the low
clouds/fog clear the eastern terminals, VFR conditions are
expected across the board through midday before the approaching
front brings lower clouds and scattered snow-showers by Wednesday
afternoon/evening.

Barnes

&&

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

$$