067
FXUS63 KILX 111630
AFDILX

Area Forecast Discussion...Updated
National Weather Service Lincoln IL
1030 AM CST Thu Dec 11 2025

.KEY MESSAGES...

- A Winter Weather Advisory is in effect for nearly all of central
  Illinois this afternoon through tonight. Storm total snowfall
  will range from 2 to 5 inches.

- Another fast-moving system will bring a period of snow on
  Saturday. The latest NBM shows a 50-80% chance of greater than 2
  inches of snow.

- A surge of bitterly cold air will result in sub-zero apparent
  temperatures Friday night through Monday morning.

&&

.UPDATE...
Issued at 1030 AM CST Thu Dec 11 2025

We are starting to see some returns on the radar for west-central
IL, but no reports at any of the ground stations of any falling
precipitation. A clipper system is still expected to move through
the forecast area today into tonight. Timing is continuing to show
snow onset by 3pm in west central IL. Snow amounts haven`t changed
as of this update with a forecast amount of 2-5 inches.

Copple

&&

.DISCUSSION...
Issued at 231 AM CST Thu Dec 11 2025

...Winter Weather Advisory Later Today into Tonight...

A short-wave trough evident on 0730z/130am water vapor imagery
over the Northern Rockies is triggering wintry precipitation
across the Dakotas early this morning. As the wave dives
southeastward, light snow will spread across Iowa and will spill
into the Illinois River Valley by early to mid-afternoon....then
further east to the Indiana border by sunset. 00z/06z models have
finally come into agreement on the exact track of the system, with
consensus placing the heaviest snowfall axis across the heart of
central Illinois. The strongest lift/deepest moisture will
coincide this evening, during which time the snow will become
moderate to heavy at times with rates perhaps approaching 1 inch
per hour in spots. Given snow to liquid ratios ranging from 9:1 to
12:1 during peak snowfall, am expecting widespread totals in the
2 to 4-inch range. A few locations along and just south of the
I-74 corridor could pick up as much as 5 inches before the snow
tapers off and comes to an end from west to east overnight. This
will be a relatively wet snow and with surface winds of 10mph or
less, am not expecting much blowing or drifting. The evening
commute will be impacted by snow-covered roads, particularly west
of the I-57 corridor where the snow will get started soonest.

...More Snow on Saturday...

After a cold and dry day on Friday with high temperatures in the
30s, an Arctic cold front will drop through the region Friday
night. As a fast-moving short-wave trough interacts with the
boundary, another period of snow will develop across central
Illinois on Saturday. While models are showing some minor
discrepancies with regards to the heaviest snowfall axis, think
the system will generally follow the differential heating
boundary between the existing snow cover and the bare ground to
the south. This will most likely place the greatest snowfall
amounts slightly south of where they will fall later today. The
00z NBM indicates a high probability (50-80% chance) of more than
2 inches of snow across all of central and southeast Illinois.
Based on the anticipated slightly further south track of the wave
and its higher snow to liquid ratios, a band of amounts
potentially in excess of 4 inches will likely set up south of I-72
where NBM probabilities for more than 4 inches currently range
from 30-40%. Stay tuned to later forecasts for more details.

...Bitterly Cold Conditions This Weekend...

As has been advertised for the past several days, another surge of
extremely cold air will arrive this weekend. High temperatures
will drop from the 30s on Friday into the single digits by Sunday.
While wind-chill values will dip below zero across parts of the
area by late Friday night, the coldest period will be Saturday
night into Sunday when apparent temperatures plunge into the -15F
to -25F range. The extreme cold will begin to ease by Monday as
boundary layer flow becomes S/SW and afternoon temperatures rise
well into the 20s and perhaps lower 30s in some spots.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 458 AM CST Thu Dec 11 2025

MVFR ceilings will generally prevail through the morning...with
the potential for ceilings climbing to VFR at the western
terminals toward midday. Any improvement will be short-lived
however, as a clipper system spreads snow into the Illinois River
Valley after 19z. While timing of snow onset is not yet 100%
certain, model consensus brings light snow to KPIA/KSPI by 20z,
then quickly eastward to KCMI by around 23z. Based on the expected
track of the system, there will be a 3-5 hour period of moderate
to heavy snow with visbys down to 1/2 mile from late afternoon
into the early evening. The snow band will gradually shift eastward
with time and visbys will improve by mid to late evening...with
the snow completely ending at KSPI by 04z...then further northeast
to KCMI by around 10z. Winds will initially be NW at 10kt or less
early this morning, then will become E/SE this afternoon as the
system approaches. Winds will then back to NE tonight.

Barnes

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 PM this afternoon to 6 AM CST
Friday for ILZ027>031-036>038-040>048-050>057-061>063-066>068-
073.

&&

$$