Des Plaines, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

426
FXUS63 KLOT 020457
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1057 PM CST Sun Feb 1 2026

.KEY MESSAGES...

- A light coating to half inch of snow is likely (70%+ chance)
  tonight into early Monday morning.

- There is a chance (30-40%) for freezing drizzle for a couple
  hours behind the snow tonight. If freezing drizzle occurs some
  icy surfaces may materialize.

&&

.UPDATE...
Issued at 856 PM CST Sun Feb 1 2026

The shortwave trough is beginning to pivot into northern IL
this evening and will continue through the area overnight.
Associated with the shortwave is a band of snow that is just
entering the I-39 corridor but will spread east through the
early overnight hours. While accumulations with the snow will
only be up to a half inch at worst, some areas of freezing
drizzle have developed behind the snow in eastern IA and
southwest WI. Forecast soundings from across our CWA continue to
show cloud top temperatures hovering in the -9 to -10C range
behind the snow which is on the more marginal side for freezing
drizzle and may support more poor quality flurries than true
drizzle. Couple this with the fact that cloud bases should
hover around 1000-1500 ft (ideally want 800 ft or lower bases),
confidence is low as to how far east the freezing drizzle will
get and how widespread it will be.

That said, with the freezing drizzle ongoing have opted to
include a formal mention in the forecast (30-40% chance). If
freezing drizzle does indeed occur it will likely only last 2-3
hours at any one location, but will likely lead to some icy
surfaces especially if they are untreated. Given the slippery
travel threat have also issued a Special Weather Statement
through midnight for areas along and north of I-80.

Regardless on the cover of freezing drizzle, precipitation is
expected to taper by daybreak Monday morning. While cloud cover
should gradually thin through the day Monday, expect partly to
mostly cloud conditions to prevail. Though with modest warm
advection temperatures should once again top out in the upper
20s to around 30 Monday afternoon.

Yack

&&

.DISCUSSION...
Issued at 212 PM CST Sun Feb 1 2026

Mid and high-level cloud cover continues to increase from west-
to-east in association with our next weather system shifting
eastward across the Mississippi Valley early this afternoon. An
area of light snow has also developed west of the area through
the morning within a region of deeper moisture and isentropic
upglide. While this area of light snow is attempting to shift
eastward into western IL at this time, it is also fighting
against drier air below 10,000 feet across northern IL.
Accordingly, it is going to take time for the snow to make
eastward extent into the Chicago metro area this evening, likely
not onsetting here until sometime after 8 or 9 this evening.
Even after it starts snowing this evening, rates are expected to
remain light, owing to rather poor forced ascent and only
modest moisture in the DGZ. So, why the potential for snow
tonight is high (70%+), the poor snow quality (small flake
sizes) and light rates is not going to amount to much (only a
light coating to as much as one half inch). The light snow is
expected to end prior to daybreak Monday morning for most.

Forecast soundings overnight indicate poor moisture in the DGZ
for a period, which suggests there to be a low, but non-zero,
chance for some light freezing drizzle. While the possibility
for this cannot be total ruled out, cloud temperatures may
remain just cold enough (~-10C) to keep any lingering light
precipitation in the form of low quality snow flakes overnight.
Also, the window for this possibility also looks limited to only
a couple hours at any given location. For these reasons, we
have opted to keep the mention out of the forecast at this time.


Aside from the chance of a few occasional flurries from a
lingering strato cu deck on Monday, conditions will remain
quiet, with highs in the mid to upper 20s.

Late Monday night through early Tuesday morning, eyes will be
on the next mid-level impulse expected to drop southeastward
along the lower-level baroclinic zone draped from the Dakota`s
into the Midwest. As it does, we could experience another
coating of snow sometime late Monday night into to early Tuesday
morning. The NBM did not offer up any POPs for this period, but
in collaboration with neighboring offices, we opted to add a
slight (20%) chance for some light snow late Monday night. At
the present time, we have only added this chance to northwestern
parts of IL. Admittedly, however, we could see the need for
these chances to be expanded into much of northern IL with
future forecast updates. Otherwise, the main chances for snow
later Tuesday with this wave are expected to quickly transition
to our southeast across the Ohio Valley.

A rather marginal lake-effect snow set-up into northwest
Indiana and along the Illinois shore will then be the next focus
for precip Tuesday night into Wednesday morning. Low inversion
heights and borderline thermo profiles indicate the precip will
be limited to isolated to scattered light showers. We have
maintained the going chance PoPs with little accumulation during
this window.

Broader northwest flow will persist midweek through next
weekend. Temps will moderate to above freezing on Thursday, and
Friday, which would be the first time in around three weeks for
much of the area. This would also come with a potential for more
active weather in the region late in the week, with chances of
accumulating snow and perhaps mixed precip. Another period of
colder conditions then appears to be in store for next weekend.

KJB

&&

.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1057 PM CST Sun Feb 1 2026

Forecast concerns for the terminals...

- Period of snow tonight resulting in reduced visibility and
  some accumulations.

- 30-40% chance for a period of freezing drizzle behind the
  snow tonight.

- Another chance for snow (20-30%) late Monday night into
  Tuesday morning.


The snow associated with a shortwave trough continues to spread
across northern IL this evening and will move into northwest IN
after midnight. While visibilities have generally been around
5-6 miles with the snow, ceilings have been lowering into the
1500-2000 ft range as snow begins. Additionally, some freezing
drizzle has developed behind the snow in eastern IA and
southwest WI and that threat does look to meander into northern
IL and maybe northwest IN later tonight. Given that forecast
soundings continue to show cloud top temperatures around -9/-10C,
confidence on the coverage and intensity of freezing drizzle at
the terminals remains somewhat low. That said, if the IFR
ceilings in IA do move overhead then the freezing drizzle threat
could increase and thus have decided to maintain the TEMPO
groups for such in the TAFs for now. Regardless, freezing
drizzle should only last around 2-3 hours at any one location
before shifting east and ending between 10-12z.

Outside of the precipitation, southwest winds have remained
breezy this evening with occasional gusts around 18-20 kts.
These gusts should remain sporadic through the night before
speeds settle around 10 kts by Monday morning. Ceilings however
look to remain MVFR through Monday morning before attempting to
lift back to VFR Monday afternoon.

Finally, another shortwave is forecast to pivot through the
Great Lakes late Monday night into Tuesday morning. While
guidance does show some snow developing with this wave, the more
limited moisture looks to make the snow more scattered in
nature. Therefore, confidence on if the snow will actually reach
the terminals or develop south of them remains low. So for now
have opted to introduce a PROB30 at the Chicago sites for this
potential.

Yack

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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