871
FXUS63 KLOT 021758
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1158 AM CST Tue Dec 2 2025

.KEY MESSAGES...

- Possible (40-60%) period of light snow Wednesday afternoon
  with any snow accumulations less than one inch.

- Well below normal temperatures through the weekend with wind
  chills -10 to -20 expected Thursday and Friday mornings.

&&

.DISCUSSION...
Issued at 216 AM CST Tue Dec 2 2025

Clouds scattered quickly as the snow ended and areas of freezing
fog quickly developed, most concentrated along the I-80 corridor/
Fox Valley in IL, currently. Visibility has improved quite a bit
here at LOT recently as stratus clouds moved back through.
Forecast soundings also suggest low level winds will increase
into the 10-12kt range over the next few hours and this may help
mix the low levels enough to limit any widespread dense fog.
Issued an SPS earlier for the entire area which expires at 10z,
with fog mention in the grids/forecast until 12z. Will take
another look for refinement before sending products this
morning. Another SPS may be needed for at least patchy freezing
fog through mid morning.

Any remaining light snow will end over the next few hours and
plan to let the rest of the winter weather advisory expire at
09z. However, untreated surfaces may still be partially snow
cover and slippery this morning.

A ridge of high pressure will quickly move across the area today
with winds turning southerly by this evening and then gradually
increasing in speed overnight with some gusts into the 20-25 mph
range possible by daybreak Wednesday morning. Low temps will
likely occur this evening, generally in the upper teens and then
temps will level off an begin to slowly rise overnight.

A strong cold front will move across the area Wednesday
afternoon into early Wednesday evening. Precip chances along and
ahead of this front remain uncertain with guidance about equally
split between just some flurries or a brief period of light
snow. Blended guidance pops have jumped to likely for much of
the central cwa Wednesday afternoon. If snow occurs, it will
likely be a high pop, low qpf event and opted to make no
changes. Snow amounts will be light, less than one inch and many
areas may see just a dusting/trace.

The cold air surges into the area Wednesday night on gusty
northwest winds into the mid 20 mph range, which will diminish
to 10 to 15 mph by daybreak Thursday morning. Low temps will
likely be in the subzero single digits across northwest IL and
in the low single digits for the rest of the area, perhaps a
little warmer downwind of Lake Michigan in northwest IN. This
temp/wind combination will likely produce wind chills in the -10
to -15 range for most areas.

High pressure will quickly move across the area Thursday and is
a bit faster in the latest guidance. This allows for some weak
warm air advection by late afternoon and then pretty decent
warming aloft Thursday night into Friday morning. Blended high
temps in the lower/mid teens may be a touch too cold, but made
no changes. However, did warm low temps Thursday night, as they
will tank Thursday evening and then level off and may slowly
warm by daybreak Friday. This still yields subzero single digit
low temps. Even if temps level off and slowly warm overnight,
southerly winds will slowly increase Thursday night into Friday
morning, keeping wind chills in the -10 to -20 range for much of
the area.

There remains quite a bit of uncertainty for a possible system
this weekend and then perhaps another system for early next
week, both of which could produce at least some accumulating
snow for parts of the area. Blended guidance low chance pops
seem fine for now. cms

&&

.AVIATION /18Z TAFS THROUGH 00Z THURSDAY/...
Issued at 1158 AM CST Tue Dec 2 2025

Key messages for the 18Z TAF period:

* IFR to MVFR for a majority of the period, lower confidence in
  cat trends

* Gusty SW winds overnight

* A chance for a period of snow early-mid afternoon Wednesday

IFR cigs hang over the TAF sites a little before 18Z. They are
very slowly trending up and are expected to lift to low MVFR
near or shortly after 18Z at the Chicago sites, and possibly
closer to mid- afternoon inland. There is a signal for a period
of VFR overnight into Wednesday morning before MVFR settles in
again during the morning. However, this signal is slowly
shrinking and guidance is trending toward continued MVFR through
the night. MVFR appears likely again by mid-morning on
Wednesday as a cold front approaches the area.

A potential for a period of snow exists along the front.
Favorable time window is 16-19Z at RFD and 18-21Z in
Chicagoland. Intensity should be light with vsby reductions as
low as MVFR, but a few tenths of an inch could get left behind.

Additionally, W winds near or below 10 kt this afternoon will
trend SW and pick up gusts between 20 and 25 kt for late this
evening and overnight. SW winds between 10 and 20 kt can be
expected ahead of the cold front tomorrow before turning to NW
in its wake.

Doom

&&

.CLIMATE...
Issued at 225 PM CST Mon Dec 1 2025

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 midnight tonight to 9 AM CST
     Thursday for the IL nearshore waters.

     Small Craft Advisory from midnight tonight to 3 PM CST
     Thursday for the IN nearshore waters.

&&

$$

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