987
FXUS63 KILX 282311
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
511 PM CST Fri Nov 28 2025

.KEY MESSAGES...

- An early season winter storm system will create significant
  travel difficulties across much of the Midwest this weekend.

- Snow will be the primary precipitation type late tonight into
  Saturday morning...before mixing with rain along/south of I-70
  by Saturday afternoon and evening.

- Snow accumulations will range from 1 to 3 inches south of
  I-70...to as much as 9 to 12 inches along and north of a Macomb
  to Bloomington line.

&&

.SHORT TERM... (Tonight through Saturday)
Issued at 146 PM CST Fri Nov 28 2025

A vigorous short-wave trough evident on 18z/12pm water vapor
imagery over the Northern Rockies will dive southeastward,
enhancing surface cyclogenesis in the lee of the Rockies across
eastern Colorado later today. As has been seen by the past several
model suites, the low will then eject northeastward to southern
Lake Michigan by early Sunday morning. Strong upglide will develop
ahead of the approaching system late tonight through Saturday
afternoon...particularly on the 295k and 300k isentropic surfaces.
Ample atmospheric moisture will flow northward from the
Gulf...with NAM precipitable water values reaching 0.50 to 0.80
and 750-700mb mixing ratios peaking at 3.0-4.5g/kg. Given the
favorable lift/moisture parameters, a significant early season
snowfall event is anticipated.

12z CAMs have a good handle on the initial onset of the
snow toward dawn Saturday...with only the HRRR suggesting the
possibility of a band of light WAA snow arriving across the
western half of the KILX CWA as early as this evening. While
clouds will definitely be on the increase, still think the
initially very dry boundary layer will prevent much snow from
reaching the ground. Have included low chance PoPs (20-40%)
along/west of I-55 between 03z/9pm and 06z/midnight accordingly,
but feel little more than flurries or very light snow will occur.
As the low approaches and synoptic lift increases markedly, the
atmosphere will quickly moisten from the top-down and snow will
develop from west to east across the area well after midnight.
Based on the latest data, it appears snow will spread as far east
as the I-57 corridor by 6am. Snow will become moderate to heavy
at times Saturday morning through mid-afternoon...with rates
perhaps reaching as high as 1-2 inches per hour at times. As the
low tracks into north-central Illinois, isentropic lift will
quickly decrease from west to east across the area by early
evening...resulting in the appreciable snowfall tapering off to
very light snow or flurries at that time.

While precipitation onset and amount have been essentially
settled, there is still some uncertainty concerning precip type
across the E/SE CWA during the afternoon and evening. Model
thermal fields are still variable...with the NAM and RGEM
maintaining the coldest boundary layer and the HRRR pushing warmer
air more aggressively northward ahead of the low. Think the
actual solution lies somewhere between these two camps. Dynamic
cooling during the strongest lift/heaviest precip will likely keep
the boundary layer cooler much like the NAM advertises. However
once the lift shifts to the east, WAA will warm surface temps as
per the HRRR solution during the evening hours. As a result, am
expecting all snow across the entire KILX CWA during the
morning...with the snow mixing with rain along/southwest of a
Rushville...to Taylorville...to Robinson line by mid to late
afternoon. As temperatures slowly climb, a light rain/snow mix may
spread as far north as the I-74 corridor during the
evening...before the low and its trailing cold front bring colder
air back into the region overnight. While any lingering precip
will be quite light late Saturday night into Sunday morning, any
moisture will freeze...creating slick conditions on surfaces that
have been cleared of snow.

The storm total snowfall forecast has not changed significantly
from previous thinking. 1-3 inches of snow is expected south of
I-70...with 3-4 inches along I-70. Further north across the heart
of central Illinois, a general 5-8 inch amount is expected. The
heaviest snow still appears to be focused along/north of a Macomb
to Bloomington line where amounts will reach 9 to 12 inches. It
should be noted that this will be a heavy/wet snow that will be
difficult to shovel. While S/SE winds will gust 25-30mph during
the snowfall, blowing and drifting will at least be partially
mitigated by the wet nature of the snow.

Barnes

.LONG TERM... (Sunday through Next Friday)
Issued at 146 PM CST Fri Nov 28 2025

A cold and wintery week is ahead in the extended. After some
lingering snow-showers Sunday morning, very cold and dry
conditions are anticipated by Sunday night. As skies clear and
winds diminish over the fresh snow cover, overnight lows will drop
into the single digits along/north of a Rushville to Bloomington
line...with teens further south across the rest of the area.
Another fast-moving but much weaker system is progged to skirt
through the region late Monday...bringing a period of light snow
Monday afternoon/night. Accumulations will be minor, generally 1
inch or less. After that, cold and mostly dry weather is on tap
through next Friday.

Barnes

&&

.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 511 PM CST Fri Nov 28 2025

Regional radar mosaic shows radar returns as far east as west
central IL, however this initial wave is virga falling from a mid
level cloud deck. Surface obs indicate -SN reaching the ground
with MVFR visibilities in central IA. This first round of snow
will work into the central IL terminals around 04-07z, likely
focused from KPIA-KBMI-KCMI through the overnight hours. Some
guidance shows vis dropping to IFR, so will need to watch trends
as this moves in. Heavier snow is expected to overspread the
entire area after daybreak with IFR cig/vis common through Sat
afternoon, and periods of LIFR/VLIFR in the heaviest snow bands.
Light/variable winds this evening will firm from the southeast
later tonight then become strong by mid morning with 25-30 kt
gusts common through afternoon.

25

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning from midnight tonight to 6 AM CST Sunday
for ILZ027>031-036>038-040>043-047>053.

Winter Storm Warning from 6 AM Saturday to 6 AM CST Sunday for
ILZ044>046-054>057-061.

Winter Weather Advisory from 6 AM Saturday to 6 AM CST Sunday
for ILZ062-063-066>068-071>073.

&&

$$