192
FXUS63 KILX 071150
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
550 AM CST Sun Dec 7 2025

.KEY MESSAGES...

- A very light wintry mix along/north of the I-74 corridor will
  come to an end this morning...with no significant travel impacts
  expected.

- The next potential for frozen precipitation will come into the
  picture on Thursday when a weak system will bring a 30-50%
  chance for light snow.

- Another surge of very cold air is expected by the end of the
  week...resulting in sub-zero apparent temperatures by Friday and
  Saturday.

&&

.SHORT TERM... (Today through Monday)
Issued at 317 AM CST Sun Dec 7 2025

08z/2am surface analysis shows a 1011mb low over southeast
Iowa with widespread light to moderate snow occurring along/north
of the I-80 corridor. Further south, precipitation is much
lighter across central Illinois...with most locations along/south
of I-72 remaining dry thus far. As the low tracks slowly eastward,
a mix of light snow/freezing drizzle will gradually come to an
end across the northern third of the KILX CWA by mid-morning.
Given temperatures hovering near 32F across this area, cannot rule
out scattered slick spots on bridges, overpasses, and untreated
surfaces: however, no major travel hazards are anticipated.
Further south, temperatures have risen above freezing and the main
weather story will be fog/drizzle. 08z/2am obs show visibilities
ranging from 2-5 miles east of the I-55 corridor. CAMs appear to
be a bit too aggressive in developing dense fog across this area
over the next few hours: however, think areas of fog will persist
across the E/SE CWA through the morning before the low tracks
further east and gradually pulls a cold front through central
Illinois. Some locations south of I-70 will see fog persisting
into the evening before visibilities finally improve later
tonight. Once the front passes, a colder airmass will settle back
into the region...resulting in overnight lows ranging from the
single digits northwest of the Illinois River around Galesburg/Macomb
to the middle 20s south of I-70. After a cloudy start to the day,
partial sunshine will return by Monday afternoon. Despite the
sun, high temperatures will remain well below normal for this time
of year in the middle to upper 20s north of I-70 and in the lower
30s to the south.

Barnes

.LONG TERM... (Tuesday through Saturday)
Issued at 317 AM CST Sun Dec 7 2025

The next short-wave trough embedded within the prevailing
northwesterly flow pattern will approach central Illinois on
Tuesday. As boundary layer flow becomes S/SW ahead of the wave
and its associated surface low, temperatures will rebound into
the lower to middle 40s. All models track the low well north of
the region across the Upper Midwest Tuesday night into Wednesday,
ensuring mild conditions with any resulting precipitation in
liquid form. Models have been trending drier south of the low
track for the past few runs, so have focused the highest PoPs
(40-60%) along/north of I-74 Tuesday night.

Once the the system passes, a colder airmass will return by
Wednesday night into Thursday. There is still considerable model
disagreement concerning one or more short-wave troughs dropping
into the region by the end of the week. The 00z GFS continues to
show a wave spreading light snow into central Illinois on
Thursday...while the ECMWF/GEM keep the snow mainly off to the
W/SW across Missouri. Given the degree of model spread at that
time range, confidence remains low for snow on Thursday. Will
maintain the current NBM PoPs, but think these will need to be
adjusted as model solutions converge over the next day or two.
Regardless of the Thursday snow chances, the main story by the end
of the week will be the colder weather. While the degree of the
cold varies among the operational models, confidence is growing
that the Friday through next Sunday time frame will be quite cold.
In fact, the 00z Dec 7 LREF shows a 40-70% chance of apparent
temperatures dropping below -10F everywhere north of I-70 by
next Saturday morning.

Barnes

&&

.AVIATION...  (For the 12z TAFs through 12z Monday Morning)
Issued at 550 AM CST Sun Dec 7 2025

IFR conditions will prevail at the central Illinois terminals
through the morning. Once a weak area of low pressure tracks into
Indiana and winds veer to N/NE, ceilings will gradually rise to
MVFR beginning at KPIA by 17z...then further south to
KSPI/KDEC/KCMI by around 21z. Will need to keep an eye on visbys
along/east of I-55 over the next few hours...as the potential
exists for patchy dense fog. Thus far visbys have generally
ranged from 2-3 miles, but think the eastern terminals will drop
into the 1/2 to 1 mile range after sunrise. Once N/NE winds pick
up behind the departing system, any morning fog will dissipate
during the afternoon. After that, the big question will be how
quickly the MVFR cloud deck will scatter. The HRRR indicates a
return to VFR at KPIA by 22z, but then suggests moisture advecting
southwestward from Lake Michigan could keep at least SCT low
clouds in the picture at the remaining TAF sites at least into the
evening. Have scattered all sites after the 03z-05z time period,
but forecast confidence is low.

Barnes

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST early this morning for
ILZ027>031-036>038.

&&

$$