627
FXUS63 KLOT 020816
AFDLOT

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

.KEY MESSAGES...

- Areas of freezing fog early this morning.

- 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 /06Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 1146 PM CST Mon Dec 1 2025

Key Messages:

- Snow will come to an end overnight.

- IFR/MVFR ceilings are favored to prevail well after the snow
  ends tonight, though confidence in exact ceiling trends is
  relatively low through the TAF period.


Most of any lingering accumulating snow will come to an end
prior to 09Z. There is an increasing chance for flurries and/or
lingering mist to keep visibilities reduced for a while longer,
however, so have pushed the return of VFR visibility back a few
hours in the TAFs to account for this possibility.

After the snow ends, IFR/MVFR stratus is generally favored to
prevail into tomorrow. Satellite observations indicate that
there are some breaks within the broader stratus shield over the
region, and some model guidance suggests that some more
scattering could occur tomorrow, so it`s plausible that VFR
conditions could end up being observed for some period of time.
However, confidence in precisely when that might occur and how
long that would occur for is low on the whole, so have continued
to take a simpler, more pessimistic approach with the TAFs and
just advertise prevailing MVFR ceilings through the TAF period
for now. Adjustments to the ceiling forecast will likely need to
be made as observational and model trends become evident.

Ogorek

&&

.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...Winter Weather Advisory until 3 AM CST /4 AM EST/ early this
     morning for INZ001-INZ002-INZ010-INZ011-INZ019.

LM...None.

&&

$$

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