486
FXUS63 KILX 101119
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
519 AM CST Mon Nov 10 2025

.KEY MESSAGES...

- A Winter Weather Advisory is in effect for portions of east-
  central Illinois through mid- morning. 2-4" of snow is
  forecast, with the highest totals occurring north of I-74.
  Visibility may fall below a half mile at times. The worst
  conditions are expected between 3 AM and 6 AM.

- Minor snow accumulations (0-1") may extend as far west as a
  Bloomington to Lawrenceville line this morning.

- Unseasonably cold this morning, with air temperatures in the mid
  20s and wind chill values as low as 10 degrees above zero.

- A warming trend is expected this week, with well above normal
  temperatures by Friday and Saturday.

&&

.DISCUSSION...
Issued at 231 AM CST Mon Nov 10 2025

An expansive, anomalous upper trough was centered over the Great
Lakes and encompassed much of the US early Mon AM. 500mb temps
were forecast to be around or slightly below -40 degC this
morning, which would be approaching some of the coldest ever
sampled in central IL per the ILX sounding climatology (the
coldest observed values were around -45 degC). These very cold
temperatures aloft have resulted in steep lapse rates,
particularly over the much warmer waters of Lake Michigan.

*** MONDAY MORNING SNOW & COLD ***

As anticipated, a robust lake effect snow band has pushed into
northeast IL tonight, with several areas near/within Chicagoland
reporting 1/4 mile vis, accumulating snow (over 2" per hour in
some spots), and isolated instances of thunder. While conditions
are not expected to be quite that intense in the ILX CWA, radar
imagery as of 120am/0720z suggests the moderate/heavy snow has
reached Kankakee, with lighter but steady snow starting to push
into the northern fringes of the ILX CWA (2 mile vis and snow
reported at Rantoul). Traffic maps are already starting to note
slowdowns along I-57 north of Paxton.

The expectations for this event have not changed all that much,
with 1-4" of snow within the advisory area but a quick drop off
with southward extent such that the highest values will be in
northern portions of Champaign/Vermilion counties. Latest NBM has
about a 40% chance of 1" of snow at CMI, increasing to over 80%
chance at Rantoul/Hoopeston. There is a 10-20% chance of 4" of
snow along/north of a Rantoul to Hoopeston line.

In terms of timing, the worst conditions for the advisory area are
likely to occur between 3am and 6am (09z-12z). During this window,
the HREF mean snowfall rates are generally between 0.5-0.75" per
hour, which will result in accumulating snow just before the peak
of the morning commute. There will also be 20-30 mph wind gusts,
and the HREF suggests a 50-70% chance that visibility will drop
below a half mile at times. Snow will taper off towards mid-
morning, lingering longest in northern portions of
Champaign/Vermilion counties as well as near the IL/IN border.

Issued a Special Weather Statement for areas roughly from
Bloomington to Lawrenceville and eastward for minor snow accums
(mostly less than 1") that could result in some slick spots and
lowered visibility during the morning commute. Normally, this type
of snow would not warrant an SPS, but given it is the first
accumulating snow of the season and occuring during a morning
commute, felt it was worthy of amplified messaging.

The other notable factor this morning is the unseasonably cold
temps, with air temps in the mid 20s as of 130am/0730z. Increasing
cloud cover may keep temps from dropping too much further, but
even in the mid 20s we`re running about 10 degrees below normal
for lows. Given the breezy northwest winds, wind chill values this
morning will drop to near 10 degrees (although the gusts may make
it feel even worse than that). If traveling (especially within
the winter weather advisory area), make sure to have appropriate
layers as these will not be pleasant conditions to be stuck out in
should something go awry while traveling.

*** REST OF THE WEEK ***

Another cold night/morning are in store into Tues, with lows once
again in the low 20s, but a warming trend is still on track for
this week. By Tues morning, a sfc high will be situated over the
deep south, with the upper trough over the eastern US and upper
ridging building over the western US coast. This will keep a NW
flow regime in place aloft, and a weak disturbance is set to
approach from the NW early Tues AM. This will result in increasing
mid/upper level cloud cover, with forecast soundings showing a
deep saturated layer aloft. The lowest 8-10 kft of the forecast
soundings are quite dry, however, so while I can`t completely rule
out some flurries it`s going to be difficult to overcome the dry
low-level air. Temps rebound into the upper 40s/low 50s on Tues,
then upper 50s/low 60s on Wed.

By Fri, the amplified upper ridge axis will be shifting closer to
IL, with another amplified trough moving onto the west coast.
Ensemble data indicates that the 500mb heights associated with the
upper ridge will be at least one standard deviation above the
mean, and correspondingly, forecast guidance continues to depict a
strong signal for above normal temps Fri and Sat. The NBM has a
40% chance of 70 degF temps for the I-74 corridor on Fri, with a
60-70% chance from SPI to LWV and southward. For Sat, there is a
70-80% chance for 70 degF temps area-wide. Normals highs for mid
November are in the mid 50s, and record highs are in the mid/upper
70s. Near-record temps are forecast (although the current
forecast keeps values a few degrees below records).

The evolution of the next system is low confidence at this stage,
as the upper pattern takes on a bit of a split flow/phased wave
pattern, with the timing/strength of both waves becoming relevant
to the resulting sfc pattern evolution. Will need to monitor the
severe storm potential with this trough Sat-Sun, but again,
confidence is quite low at this time. The 09.00z run of the GEFS-
based CSU-MLP highlighted a broad area of severe risk across the
eastern Plains and Midwest, but this signal has not been
consistent from run to run and was not really corroborated by
other ensemble families. The Grand Ensemble only registered a
10-20% chance of both MUCAPE above 250 J/kg and 30 kts of shear,
and 250 J/kg of MUCAPE is hardly notable. At any rate, there is a
40-50% chance of rain Sat night through Sun.

Erwin

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 518 AM CST Mon Nov 10 2025

An intense snow band continues across east-central IL. This band
will stay just east of KBMI/KDEC, but LIFR/VLIFR conditions have
been observed in KCMI. Radar imagery suggests the heaviest snow
should shift south of the terminal by 12z, but can`t rule out
additional showers at KCMI reducing vis below 1 mile during the
first few hours of the period. Breezy northwest winds continue
through the morning, with gusts weakening into early afternoon.
This evening, winds turn to westerly, then overnight become
southwesterly. From 15z onward, VFR conditions are expected at all
terminals. Cloud cover gradually decreases during the day, then
mid- level cloud cover builds back in overnight.

Erwin

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 AM CST this morning for ILZ045-
046-055>057.

&&

$$