776
FXUS63 KILX 252341
AFDILX

Area Forecast Discussion...Updated Aviation
National Weather Service Lincoln IL
541 PM CST Tue Nov 25 2025

.KEY MESSAGES...

- Strong westerly winds are expected on Wednesday, with gusts of
  40 to 50 mph being common. This may lead to travel difficulties
  on north-south oriented roadways.

- Below normal temperatures are expected Wednesday through Friday,
  with highs in the mid 30s to low 40s. Breezy winds will make it
  feel even cooler on Wednesday and Thursday.

- There is a 50-80% chance of 2" of snow north of I-72 this
  weekend (20-50% to the south). Those with travel plans are urged
  to monitor forecast updates, and begin preparing for travel
  impacts, particularly across the northern half of Illinois on
  Saturday.

&&

.DISCUSSION...
Issued at 208 PM CST Tue Nov 25 2025

*** THIS EVENING ***

A sfc low was positioned over SW MN at 0130pm/1930z on Tues, with
a strong cold front arcing southward across central IA and into
MO. A narrow band of rain will accompany this front as it treks
across central IL this evening (between about 7 PM and midnight).
Instability is low, so no thunder is expected, and the progressive
nature of the front will keep rainfall amounts light (less than a
tenth of an inch). As the front passes, expect temps to fall
quickly into the 30s, and breezy northwesterly winds to develop.

*** TONIGHT - FRIDAY ***

A tight pressure gradient will be in place early Wed AM as a sub-
995mb sfc low deepens over northern WI. Following the frontal
passage, CAA and pressure rises will result in subsidence that
aids in mixing strong wind gusts to the surface. The wind advisory
was expanded to encompass the entire ILX CWA. Winds may not quite
reach advisory criteria (gusts over 45 mph) south of I-72, but it
will be close. The latest Grand Ensemble had a 70-100% chance for
gusts over 40 mph north of I-70, and a 50-70% chance south of
I-70. The strongest winds are expected near/north of I-74, where
peak gusts could exceed 50 mph (10-30% chance per the latest
HREF). The westerly wind direction will result in travel
difficulties for high profile vehicles on north-south roadways
such as I-55, I-57, and I- 39.

Otherwise, no major changes to the temperature forecast for the
latter half of this week. It will feel raw on Wed and Thurs as
below normal temps and windy conditions keep the daytime apparent
temps below freezing both days. A strong, expansive sfc high
pressure (over 1032-mb) will be centered over MO by Fri AM,
offering a reprieve from the gusty winds, but also providing
better radiational cooling conditions that allow air temps to fall
into the teens early Fri morning. High temps Wed-Fri will be in
the 30s to low 40s.

*** WEEKEND SYSTEM ***

Forecast confidence is quickly increasing that wintry precip will
occur this weekend, impacting post-holiday travel. Noted stark
differences between the GFS/GEFS and the ECMWF/EC Ens in
yesterday`s guidance, but the GFS/GEFS have trended much closer to
the ECMWF solution today. Additionally, cluster analysis
(designed to group similar ensemble members to compare and
contrast potential scenarios) is producing similar output
regardless of how the ensemble members are clustered.

From the synoptic perspective, this system will be driven by an
open upper trough digging quickly across the Intermountain West
and ejecting onto the Plains by Sat AM. Ahead of this, lee
cyclogenesis will lead to gulf moisture transport across the
southern Plains and into portions of the Midwest. WAA/isentropic
upglide will lead to precip development late Fri night into Sat,
with widespread precip continuing into Sat.

There is an increasingly robust signal for snow accumulations, but
before diving into those, did want to note the greatest
uncertainty with this system is still related to location and
timing of the rain- snow line (and any other p-type transitions).
It appears a rain-snow transition will occur somewhere across the
region during the day or evening on Saturday (occurring from south
to north). Will also need to monitor the timing of that
changeover relative to the development of a WAA-driven warm nose.
Guidance still isn`t showing a robust signal for freezing rain
(the warm nose is only near or slightly above 0 degC), but can`t
let our guard down in a setup like this, especially since there is
some potential for earlier snow accumulations during the day on
Saturday to hold sfc temps below freezing longer than models
depict (which would increase the potential for a window of
freezing rain). All of this is to say, despite increasing
confidence in some kind of wintry impacts this weekend, the
specific timing of the various p-types is still low confidence.
It`s important to remember this system won`t be reaching the west
coast of the US until the evening hours of Thanksgiving (and
therefore won`t be sampled by the radiosonde network until that
time).

At this point, the best signal for snowfall is in areas north of
I-72. The latest NBM 10th percentile (90% chance of higher
amounts) is depicting a trace to 1" north of I-72 (up from no snow
in yesterday`s guidance). The ECMWF Ensemble based "Shift of
Tails" product continues to produce a strong signal for a
significant snowfall event, with both high EFI and high SOT
values. That signal translates to a 20% chance for over 6" of snow
along the I-72 corridor, increasing to a 30-40% chance along and
north of the I-74 corridor. Given the marginal thermodynamics, I
anticipate snow-to- liquid ratios of less than 10:1, meaning a
wet, heavy snow is more likely than a fluffy, dry snow. (This is
also important to note if viewing snow probabilities from
specific ensembles, as the output often assumes a 10:1 ratio and
may therefore be an overestimate of the true probability).

Those with travel plans this weekend are urged to check back for
additional updates. The probability of wintry travel impacts is
steadily increasing, particularly across the northern half of
Illinois.

Erwin

&&

.AVIATION...  (For the 00z TAFs through 00z Wednesday Evening)
Issued at 541 PM CST Tue Nov 25 2025

MVFR cigs will be predominant, although with a few breaks in the
clouds, as a cold front approaches this evening. Along the cold
front, a few showers can be expected, as well as some isolated IFR
cigs from around 00Z to 04Z. Behind the front, a period of VFR
cigs can be expected, although MVFR cigs are likely to return by
07Z-09Z. MVFR is expected until around 20Z. Winds SW 5-10 kts,
increasing and becoming W behind the front. Winds reaching 20-25
kts with gusts 35-40 kts by 12Z.

37

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory from 3 AM to 6 PM CST Wednesday for ILZ027>031-
036>038-040>057-061>063-066>068-071>073.

&&

$$