643
FXUS63 KILX 100458
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
1058 PM CST Tue Dec 9 2025

.KEY MESSAGES...

- Strong northwesterly winds gusting 40-50 mph will accompany
  scattered snow showers Wednesday morning. Be prepared for sudden
  drops in visibility if driving.

- Snowfall is anticipated from Thursday night into Friday morning,
  with a 20-40% chance of greater than 2 inches of snow along and
  north of a Macomb to Robinson line.

- Very cold air will affect central Illinois this weekend, with a
  50% chance of sub-zero wind chills north of I-72/Danville
  Saturday morning. Wind chill temperatures will be even colder on
  Sunday morning.

&&

.UPDATE...
Issued at 920 PM CST Tue Dec 9 2025

A 991-mb sfc low is positioned near Minneapolis, MN, as of 9pm/03z,
and will quickly track towards Grand Rapids, MI, by sunrise
Wednesday. Short-term forecast largely remains on track, with
low- level WAA resulting in a swath of light rain, currently in
the vicinity of the IL River Valley as of this writing. No changes
were made to the wind advisory, but will note that 00z guidance
trended less aggressive. The 09.12z HREF run had a 50-70% chance
of gusts over 45 mph, while the latest run (10.00z) decreased to a
20-50% chance.

Made some minor edits to PoPs on Wed to increase snow chances
slightly, as an early look as 00z guidance suggests a broader
region of light snow on the backside of the low. Model soundings
and precip depiction suggest the squall potential is lower than
previously forecast, but still can`t rule out some isolated squall
activity. The HREF probability of visibility below 1 mile did not
change appreciably between the 00z and 12z runs (40-60% chance
north of I-72/Danville), and the expected timing of the snow did
not change much either (most likely between 4am-noon, shifting
west to east in time).

Erwin

&&

.DISCUSSION...
Issued at 244 PM CST Tue Dec 9 2025

Temperatures have warmed above freezing this afternoon throughout
central Illinois, with wet bulb temperatures anticipated to
support rain at the surface when precipitation begins this evening
in association with a low moving southeast across Minnesota and
into southern Wisconsin. The greatest coverage of rain should be
just ahead of the low pressure trough as it moves across the area
late tonight. Of greater impact will be the west/northwest winds
behind the surface trough, continuing as a cold front moves
through Wednesday morning. Wind speeds at the top of the mixed
layer are around 50 knots, and we anticipate that any convective
elements which may develop ahead of the cold front may enhance
wind gust speeds. We`ve issued a Wind Advisory for much of the
forecast area from midnight to noon. Snow showers potentially
developing near the cold front Wednesday morning could be
responsible for rapid drops in visibility when combined with the
strong winds. With not much accumulation anticipated, the sudden
visibility changes will likely be the primary impact from any
snow.

Attention then turns to our next clipper system due to arrive in
the Thursday night/Friday morning time frame. With a cold
thermodynamic profile and lift peaking in the dendritic growth
zone, this could be an efficient snowfall producer despite its
quick movement. Snowfall may be maximized just north of the low
where the greatest precip residence time is. Amounts observed with
a fast-moving high SLR event like this will probably be highly
sensitive to the track of the low, with 90th percentile amounts
along the northern edge of the forecast area being around 4
inches.

Cold air returns in earnest this weekend, with a ~1040 mb high
moving out of south-central Canada into the Midwest. Though wind
speeds at the leading edge of this high are not forecast to be
extreme, it doesn`t take much wind to bring wind chills down
substantially. The coldest wind chills are anticipated on Sunday
morning, with most likely values ranging from 10 to 20 degrees
below zero. In addition, some light snow is anticipated along the
baroclinic zone at the leading edge of the high Saturday, with a
30-50% chance of greater than 1 inch of snow north of
I-72/Danville.

AAT

&&

.AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
Issued at 1058 PM CST Tue Dec 9 2025

A messy aviation forecast exists this period as a low pressure
goes by to the north. Scattered light rain showers are ongoing
near KPIA/KBMI, spreading east in time. Additional rain showers
are possible through 10-11z. LLWS will persist through about
10-11z as well before subsiding. The latest KILX vertical wind
profile observed 45 knot winds out of the southwest at 2 kft AGL.
2 kft wind speeds could increase to as much as 55 knots as the LLJ
increases in strength. Ceilings drop to MVFR around 10-12z, then
remain MVFR through the period. Sfc winds turn westerly overnight,
then northwesterly into the day on Wednesday as a front moves
through. Gusts as high as 35-40 kts are possible, mainly between
09-18z. Precip is expected to change to light snow Wed morning,
with some visby reductions looking increasingly likely at the
northern terminals. Isolated snow showers could drop vis as low as
1 mile, although this potential has decreased compared to early
forecasts.

Erwin

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until noon CST Wednesday for ILZ027>031-036>038-
040>045-047>056-061-062-066.

&&

$$