867
FXUS63 KLOT 031749
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1149 AM CST Wed Dec 3 2025

.KEY MESSAGES...

- Some light snow expected to develop this afternoon, possibly
  mixed with some freezing drizzle at times.

- Well below normal temperatures Wednesday night through the
  weekend, with the coldest period bringing minimum wind chills
  of about 10 to 20 below Thursday morning and Thursday evening.

- Additional chances for snow Saturday night-Sunday and again
  early next work week.

&&

.UPDATE...
Issued at 1032 AM CST Wed Dec 3 2025

Late this morning a cold front stretched from northern Lake
Michigan southwest across southern Wisconsin and into eastern
Iowa. This cold front is associated with an amplifying northern
stream trough over the Great Lakes. Meanwhile, a southern stream
shortwave trough is noted on water vapor imagery zipping
east across southern Iowa. Ascent in advance of this feature can
likely be implied by the blossoming area of mid level echos
evident on regional WSR-88D mosaic over northern Missouri into
central/northern IL. This southern stream shortwave is progged
to phase with the digging northern stream trough today resulting
in pretty potent jet streak developing over northern IL this
afternoon. Strong upper level divergence in response to the
developing jet streak will lead to deep strengthening ascent and
strengthening low level convergence along the low level frontal
boundary.

Already seeing some light precipitation developing in a narrow
band from east central IA across northern IL. Given the expected
increasing ascent through the afternoon, would expect this
precipitation to expand in coverage heading into the afternoon.
Despite the deep ascent, recent ACARS soundings from MDW depict
a notable mid-level dry layer, which is also reflected in
forecast soundings this afternoon. These forecast soundings
this afternoon are teetering on the threshold for whether ice
nuclei necessary for snow will be present, leading to some
concern for some freezing drizzle at times. While there is some
threat for FZDZ at times over most of the area, forecast
soundings do suggest that southern/southwestern portions of the
CWA may be most favored to lose the necessary cloud ice for
snow. These areas stand the best chance for temps to reach or
climb just above freezing with precip transitioning to just
plain DZ.

Low confidence in how widespread of a problem FZDZ will become
and with most roads still treated from recent snowfall, opted to
hold off on a winter wx advisory. Will be monitoring
observational trends closely this afternoon for any indications
that FZDZ threat will become more widespread. Otherwise, snow
could result in a coating to maybe a half inch of accumulation,
mainly near and south of the I-88/I-290 corridors.

- Izzi

&&

.DISCUSSION...
Issued at 240 AM CST Wed Dec 3 2025

The gusty south/southwest winds have resulted in low drifting
snow blowing onto some roads early this morning. Added patchy
blowing snow to the grids/forecast through 15z this morning,
when winds will diminish some across the north and then across
the rest of the area early this afternoon. Trends will need to
be monitored for this end time and whether low drifting snow
develops again later this afternoon into this evening.

A strong cold front will move across the area this afternoon
into early this evening shifting southwest winds to the
northwest. There is a low chance for snow showers along and
ahead of this front and made no changes to the going forecast
pops of 20-40 percent. The HRRR is the only model suggesting
that if any precip were to develop, it could be in the form of
some patchy freezing drizzle. With confidence low on whether
there is actually precipitation today, no mention with this
forecast, but trends will need to be monitored.

No changes to the forecast or reasoning for temperatures tonight
through Friday morning. Main takeaway will be the wind chills
which will be in the -10 to -15 range overnight into Thursday
morning and again Thursday night into early Friday morning.
There may be a few areas that dip to -20 for wind chills, but
these are not expected to be prolonged or widespread. Warm air
advection early Friday morning should allow temps to level off
and then slowly rise toward daybreak Friday morning.

There continues to be high uncertainty for precip chances in
the extended with some mention of blended chance pops from
Saturday night through the middle of next week. The one trend
that appears to be emerging is there could be a clipper parade
next week, with the potential that one or more of these pass
north of the local area, which would potentially allow temps to
moderate some. If there is precip falling with what will likely
be cold ground, some mixed precip would be possible, but way
too much uncertainty from this distance. cms

&&

.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1149 AM CST Wed Dec 3 2025

Forecast concerns for the terminals...

- Period of light snow this afternoon through early evening

- 20-30% chance for some freezing drizzle to mix in mainly at
  MDW and GYY and points south

- Increasing northwest winds behind a cold front this evening
  with 20 kt gusts expected


An arctic cold front is moving through the area this morning
which has resulted in an uptick in snow showers across northeast
IL and northwest IN. While snow is expected to persist through
early evening (ending 23-01z at the terminals), accumulations
look to be rather limited with amounts generally under half an
inch expected. However, there is a chance for some freezing
drizzle to mix in this afternoon mainly at MDW and GYY and
points south. Forecast soundings continue to show a loss of
cloud ice this afternoon as the front moves through, but recent
aircraft soundings out of MDW contradict this by showing a
fairly saturated atmosphere especially in the snow growth
region. So while the freezing drizzle is becoming lower
confidence (20-30% chance) have opted keep a TEMPO group going
for now for this potential especially with some FZDZ being noted
in central IL. If freezing drizzle does materialize it would
also result in a period of IFR ceilings and visibilities.

Precipitation is expected to taper this evening as the front
exits with winds becoming northwest and breezy in its wake. Wind
gusts will likely be in the lower 20 kt range this evening
through the predawn hours Thursday due to deeper mixing. Though,
as a surface high moves overhead Thursday morning winds will
subside into the 5-10 kt range with directions gradually
becoming southwest Thursday afternoon. As for ceilings, expect
the ongoing MVFR ceilings to persist through midnight before
clouds scatter and allow VFR conditions to return through the
rest of the TAF period.

Yack

&&

.CLIMATE...
Issued at 542 PM CST Tue Dec 2 2025

Updated at 250 PM CST Tue Dec 2 2025

Here are the current record low temperatures for Thursday into
Friday this week:

Chicago           Cold High       Low
Thursday 12/4     13 (1991)      0 (1893)
Friday 12/5                      4 (2005)

Rockford          Cold High       Low
Thursday 12/4      7 (1991)     -4 (1991)
Friday 12/5                     -5 (2005)

- Izzi

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 9 PM this evening to 9 AM CST
     Thursday for Winthrop Harbor IL to Gary IN.

     Small Craft Advisory until 3 PM CST Thursday for Gary to Burns
     Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

Visit us at weather.gov/chicago