186
FXUS63 KLOT 101137
AFDLOT

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

.KEY MESSAGES...

- A period of dangerous and intense wind blown lake effect snow
  will continue this morning, with impacts to travel generally
  along and east of I-57 and I-355 through noon in Illinois.

- Meanwhile, in northwestern Indiana, a break in lake effect
  snow is possible this morning before snow returns in an
  eastward-moving band this afternoon.

- Travel conditions beneath the snow bands will be difficult
  with low visibility and quick accumulations on roadways.

- A quickily-moving system may deliver a dusting of snow on
  Tuesday.

- A gradual warming trend, possibly accompanied by periods of
  breezy winds, is expected toward the middle of next week.

&&

.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 /12Z TAFS THROUGH 18Z TUESDAY/...
Issued at 537 AM CST Mon Nov 10 2025

Key Aviation Messages for the current TAF period:

- Another band of lake effect snow over southeastern Wisconsin
  will move south across the Chicago terminals through the
  morning reducing conditions once again to V/LIFR

- Gusty northwest winds will prevail through the afternoon
  before subsiding. Lighter winds after 00Z will slowly turn to
  the southwest.

There is a brief break in the snow for many of the Chicago
terminals. There is a band of lake effect snow along a KDPA
to KRAC line. This band will move southward and be the next
chance for impactful snow. While accumulations will may "only"
be another 1 to 3 inches (depending on how fast it moves over
any one terminal), it will have the ability to reduce vis below
1SM. Northwest winds remain gusty between 20 to 25 knots, and
occasional gusts to 30 knots is possible when the band is
overhead and allowing BLSN to remain in the TAFs. The highest
uncertainty remains in the timing of when the band moves
southward. Timing was adjusted to account for a later arrival
this morning, but may need to be refined later this morning once
the band starts to move. Other than some lingering flurries
behind it, snow will come to an end later this morning (early
afternoon for NW Indiana).

VFR conditions are expected this afternoon (and through the end
of the TAF). Winds will remain gusty through the afternoon and
gradually diminish toward 00Z, becoming southwesterly tonight.

Near KRFD...
VFR conditions expected. The main impacts will be from gusty
northwest winds up to 25 knots, likely subsiding late afternoon
Monday. Winds will turn southwest after 00Z as they diminish and
eventually become southerly around daybreak tomorrow.

DK

&&

.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 Storm Warning until 9 AM CST this morning for ILZ006.

     Winter Weather Advisory until noon CST today for ILZ013-ILZ033-
     ILZ039-ILZ104-ILZ106-ILZ107.

     Winter Storm Warning until noon CST today for ILZ023-ILZ103-
     ILZ105-ILZ108.

IN...Winter Weather Advisory until 1 PM EST this afternoon for
     INZ019.

     Winter Storm Warning until 6 PM CST this evening for INZ001-
     INZ002.

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

LM...Gale Warning until 6 AM CST early this morning for the IL and
     IN nearshore waters.

     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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