761
FXUS63 KLOT 100811
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
211 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 /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1137 PM CST Sun Nov 9 2025

Key Aviation Messages for the current TAF period:

- Moderate to heavy wind blown lake effect snow creating drastic
impacts down to VLIFR conditions. Main uncertainties are for
any "improvements" between bands of snow

- Gusty northwest winds will likely prolong BLSN issues at the
Chicago metro terminals until winds subside late day Monday.

The initial push of snow that dropped vis down to 3/4SM at
Chicago terminals is pushing southwestward toward KPIA. However,
the next band of snow is right along the lake shoreline at the
time this discussion was published. Currently conditions at
Chicago terminals are VFR, but with the next band about to move
onshore, the TAFs were sent with worse conditions due to the
expectations that things will deteriorate quickly after 06Z.
This band will be have more vigorous snow rates and strong gusty
winds. Low vis is expected, but may exceed expectations and
become sub-1/4SM. Additionally, buoys have already reported
gusts to 31 knots, and while 35 knots is in the TAF, it is
entirely possible that gusts touch 40 knots at times. It is
possible the the TEMPO from 06Z to 09Z is a hair long, but have
moderate confidence that there could be 3 hours of really
intense snow rates.

Looking at regional radar, there is a long lake oriented band
off the Wisconsin shoreline moving southward. This band will be
"Round 2" as it moves into Illinois. There will the expectation
is that there will probably some time of "break" in the intense
snow before it moves southward (longer at KMDW and KGYY). Can`t
rule out some quick VFR conditions, but felt more prudent to
leave IFR/MVFR conditions for ongoing snowfall. Nevertheless, a
second round of intense lake effect snow is expected before
daybreak. The is slightly lower confidence in the timing of this
band. In fact, we may not know the exact timing until the
scheduled 09Z amendments when we can see "the white`s of its
eyes". But again, vis and cig reductions down to LIFR if not
brief VLIFR is possible once again. With this band more focused
closer to the lake shoreline, terminals farther inland like
KDPA should still see some light snow, but more VFR or
occasional MVFR conditions.

Most guidance has the band of lake effect snow moving eastward
toward northwest Indiana after 14Z (lower confidence in the
timing of its exit east). While the precipitation may slowly
taper off with a return to VFR conditions, northwest wind gusts
20 to 25 knots will prevail allowing providing the risk for
blowing snow from accumulated snowfall to continue into the late
morning/early afternoon. Its possible the timing of BLSN ending
is a little long, but wind gusts are not expected to truly
subside until at or just before 00Z. VFR and winds around 10
knots and subsiding are expected after 00Z.

Near KRFD...
A flurry or two is possible through daybreak, but otherwise
snow free conditions are expected. The main impacts will be
from gusty northwest winds up to 25 knots (cannot rule out
isolated to 30 kt through daybreak), likely subsiding late
afternoon Monday.

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 6 AM CST early this morning for
ILZ006.

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

Winter Storm Warning until noon CST today for ILZ023-ILZ103-
ILZ104-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.

&&

$$

Visit us at weather.gov/chicago