153
FXUS63 KLOT 101756
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1156 AM CST Mon Nov 10 2025

.KEY MESSAGES...

- Lake effect snow will lead to hazardous travel through mid
  afternoon in northwest Indiana.

- A quick moving system may produce a dusting of snow Tuesday
  morning (20-30% chance).

- A gradual warming trend is expected through the end of the
  week.

&&

.UPDATE...
Issued at 1120 AM CST Mon Nov 10 2025

After a lull in the lake effect snow this morning, the band has
shifted back into northwest Indiana late this morning.
Visibility has dropped to 1/4 mile or less directly beneath the
band with snowfall rates in the 1 to 1.5" per hour range.
Unsurprisingly, webcams show roadways have quickly become snow
covered. This lake effect band has had remained fairly
progressive as it rounds the lake which should help limit
additional accumulation to closer to the 2-4" range, though
localized higher amounts remain possible. Regardless, if
traveling in northwest Indiana this afternoon be prepared to
encounter hazardous winter travel conditions.

Any remaining winter headlines for Illinois counties will be
allowed to expire at noon today with a Winter Weather
Advisory still in effect through the afternoon for northwest
Indiana.

High temperatures today will vary based mainly on residual
snowpack, with highs in the mid 30s in largely snow-less areas,
with upper 20s to lower 30s where the snowpack is deepest.
Continued breezy northwest winds will lead to wind chill values in
the 20s through the day and teens overnight.

Petr

&&

.DISCUSSION...
Issued at 211 AM CST Mon Nov 10 2025

Through this evening:

The much-anticipated lake effect snow event is underway.

A recent surface analysis augmented by regional water vapor
satellite and radar data depicted a 1018mb low pressure system
centered near Rensselaer, Indiana beneath an upper-level polar
shortwave centered over Pontiac, Illinois. A band of intense
lake effect snow with occasional radar reflectivity near 50 dBZ,
echo tops near 20kft, periods of graupel (soft hail), and
lightning strikes extends from northern Lake Michigan southward
into northeastern Illinois and right into a hybrid deformation
zone along the Illinois and Indiana state line on the the
northwestern side of the low pressure system. Snow intensity has
thus far have been maximized in the hybrid deformation zone
where low-level convergence and synoptic-scale lift are
maximized, with spotter reports confirming snow rates of 3
inches per hour. Meanwhile, snow rates along the Illinois
shoreline of Lake Michigan have been closer to 1-2"/hr, possibly
owing to periods of graupel at the expense of snow. Regardless,
when combined with observed wind gusts of 35 to locally 45 mph
(highest near the Lake Michigan shoreline), visibility and
overall driving conditions are very poor under the lake effect
snow bands. Needless to say, this is quite an impactful but
localized event unfolding across parts of our area.

Over the next 3 to 6 hours, the polar shortwave and associated
surface mesolow will shift southward, dragging the hybrid
deformation zone along the I-57 corridor and into central
Illinois. The intensity of snow tied to the mesolow should
lessen somewhat with time as it moves further from Lake
Michigan, though quick accumulations of 2 to 4 inches of snow
(locally higher) are on track along and east of I-57 through
daybreak. Note that accumulations may be relatively minimized in
Jasper and Benton counties given the center of the low pressure
system will move directly overhead. Anyway, while a lot of
focus has been on the lakeshore with this event, don`t want to
underplay the impactful morning commute along the I-57 corridor
and points east. Take it slow out there!

As for the lakeshore... The dominant lake effect snow band is
plowing into Lake, far northern Cook, and eastern DuPage
counties at press time. Scattered but still intense echoes are
streaming into central Cook county as well. With the mesolow
and polar trough eventually taking a southeastward jog later
this morning, increasing westerly components to the low-level
wind field should begin to push the dominant band of lake effect
snow southeastward. We time the band to shift across Cook
county and into far northern Will counties between 7 AM and 12
PM, and then across Lake and Porter counties in northwestern
Indiana between roughly 12 PM and 4 PM. While the band of snow
will be transitory, intense snow rates of 2 to 3 inches per hour
will make for a very difficult morning commute. Should the band
stall for an hour or two at any given location, travel
conditions could become locally impossible. Travel is
discouraged beneath the snow band this morning.

By the time snow is done this afternoon, snow totals will
probably vary pretty dramatically across the area. Still think
that localized double-digit totals are a real possibility,
particularly in the southeastern Cook/eastern Will/Lake (IN)
county region as well as in eastern Lake (IL)/far northeastern
Cook counties.

Finally, opted to keep all headlines (Winter Storm
Warnings/Winter Weather Advisories) as-is for the time being.
It`s possible that some of the products will be able to be
cancelled early (particularly in Illinois). The day shift will
be best positioned to evaluate the current location of
accumulating snow to determine any adjustments.

Borchardt


Tonight through Sunday:

Any remaining lake effect snow across far northeast Porter
County will be ending early Monday evening as a fast moving
ridge of high pressure crosses the cwa Monday night. A weak
disturbance will move southeast in fast northwest flow early
Tuesday morning with guidance continuing to show an earlier
arrival. While precipitation amounts will be light, precip type
will likely be all snow with the earlier and colder air aloft.
Surface temps also appear to remain below freezing through mid
morning. Several runs and now some of their ensembles are
showing a dusting of snow accumulation across parts of northern
IL. No changes to the low chance blended pops, but if current
trends continue, higher pops for a dusting of snow accumulation
may be needed.

Southwest winds will increase Tuesday morning as the gradient
tightens with gusts into the 30-35 mph range possible. Wednesday
also looks breezy with westerly winds gusting into the 30 mph range.

Generally dry and warmer conditions are expected for the end of the
week though a few showers may be possible as a warm front lifts
across the area Friday night into Saturday. While high temps may
already be in the upper 50s/lower 60s Friday, this warm front could
help push highs well into the 60s for much of the area for Saturday.
A deep trough moving across the western U.S. the develops into an
upper low next weekend and then slowly moves east across the region,
bringing the next chance of rain to the area. cms

&&

.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1156 AM CST Mon Nov 10 2025

Lake effect snow has ended for the northeast IL terminals, with
snow expected to end with an hour at GYY. VFR conditions are
expected through late tonight. An axis of strong warm air
advection around 700-800mb will then lift ENE across the
terminals from the pre-dawn hours through mid-morning. Moisture
in this layer may be marginally favorable for a period of snow
with MVFR visibility, so have included a PROB30 during this
window at all sites.

NW winds will continue to gust to around 20 knots through
sunset. WNW winds around 10 knots this evening will then back SW
through daybreak Tuesday. With a 40 knot LLJ around 4kft, some
sporadic gusts above 20 knots are also possible tonight. As
daytime mixing ensues, SSW winds will frequently gust over 25
knots to possibly 30 knots.

Kluber

&&

.MARINE...
Issued at 211 AM CST Sun Nov 9 2025

Periods of north to northwesterly gale force winds to 40 kt will
continue this morning as a low pressure system centered near the
IL/IN state line drops southward. Gusts may decrease in
frequency by mid-morning as the low pulls further away, with
relatively highest frequency west of a lake effect snow band
moving eastward along the Lake MIchigan shoreline. Finally,
waterspouts will continue to be possible in any lake effect snow
band.

NWS Chicago

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory until noon CST today for ILZ103-ILZ104-
     ILZ105-ILZ108.

IN...Winter Weather Advisory until 6 PM CST this evening for INZ001-
     INZ002-INZ010-INZ011.

LM...Small Craft Advisory until midnight CST tonight for the IL
     nearshore waters.

     Small Craft Advisory until 6 AM CST Tuesday for the IN
     nearshore waters.

&&

$$

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