546
FXUS63 KLOT 281726
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1126 AM CST Fri Nov 28 2025

.KEY MESSAGES...

- Winter Storm Warning in effect for all of our Illinois and
  Indiana counties for late tonight into Saturday night.

- Impactful snow is expected late Friday night through Saturday
  night. There is a >90% chance for 6"+ amounts and higher end
  travel impacts along and north of I-80.

- Well below normal temperatures will persist into or through
  next week, perhaps with additional chances for snow (Monday
  afternoon and night).

&&

.UPDATE...
Issued at 1116 AM CST Fri Nov 28 2025

While no substantial forecast changes have been made at this
time, there is enough 12Z model support to warrant upgrading the
remainder of the Winter Storm Watch across the southeast CWA to
a Winter Storm Warning. There continues to be some concern that
a surging mid-level dry slot and warming low-level profile will
quickly end most accumulating snowfall chances in the original
watch area. However, given a relatively short period (9 hours
or less) of higher snowfall rates, increasing southeast winds
gusting to 30 mph, and associated impacts with holiday travel,
it was determined that a Winter Storm Warning is warranted for
this area.

Kluber

&&

.DISCUSSION...
Issued at 259 AM CST Fri Nov 28 2025

Through Saturday Night...

Upgraded the winter storm watch to a winter storm warning for
most of the area with increasing confidence for 6+ inches of
snow. Maintained the winter storm watch for the far southeast
cwa where snowfall amounts are expected to be less and there is
some potential for a mix/change to light rain/drizzle late
Saturday afternoon into Saturday evening.

Overall forecast reasoning remains on track with no significant
changes to the forecast this morning. Light snow is expected to
spread across northern IL late tonight/early Saturday morning
with light snow falling across much of northern IL, north of
I-80 by the predawn hours. The snow will then increase in
intensity Saturday morning with the heaviest snow falling during
the afternoon and then slowly tapering off in intensity from
southwest to northeast Saturday evening. The snow will likely
end completely early Sunday morning with perhaps some lingering
flurries of snow showers later Sunday morning. The blended pops
are in the high chance range and this seems a bit high, but did
not make any changes. Lake effect snow showers may continue
across far northwest IN, especially Porter County with
additional snow accumulation possible and the winter storm
warning may need to be extended for Porter County for these lake
effect snow showers.

QPF amounts remain fairly steady from the models, generally
ranging from 0.9 inches in the northwest and western cwa, to
perhaps as low as 0.6 inches across the southeast cwa. Have
generally maintained the snow ratios from the previous forecast,
which for the bulk of the area may only be in the 11:1 or 10:1
range, perhaps a bit higher across the northwest cwa and a bit
lower across the far southeast cwa. Combining these brings storm
total amounts for much of the warning areas into the 6-10 inch
range. Its possible areas where the watch remains in effect
could reach 6 inches, but confidence is too low to upgrade those
areas at this time. For areas northwest of an Ottawa to Aurora
to Waukegan line, snow totals may be more in the 10 to possibly
12 inch range and a separate segment may eventually be needed
but for now have just highlighted locally higher amounts for
those areas. The track of the low will also need to be watched
closely. Any north shift to the low track could have some large
impacts on snow amounts.

Snowfall rates will likely be in the one inch range for several
hours Saturday afternoon with some potential for a few hours of
rates of 1-2 inches an hour, especially across northwest IL. cms

Sunday through Thursday:
Issued at 301 PM CST Thu Nov 27 2025

A 1035-1040 hPa high building into the Great Plains impinging
on the low over Lake Huron and Georgian Bay on Sunday will
induce strong gradient winds and a modest 3-5mb/3hr pressure
rise over much of the area. Some shallow blowing and drifting
snow will likely persist for open areas conditional on a drier
character of the expected snow pack. Will include patchy
blowing snow in the forecast for now, with the greatest concerns
on N/S-oriented roadways in open areas west of the Fox River
Valley. Additionally, ongoing strong CAA with shallow stratus
under a steadily lowering subsidence will support some lingering
light snow showers or flurries well into the day Sunday. The
lower inversion will also limit lake effect snow intensity near
the lake in northwest Indiana, but additional minor
accumulations are probable for northeast Porter County.

The inversion should lower enough to erode remaining stratus
Sunday night as the surface ridge edges toward the area. As long
as stratus does not persist well into the night, diminishing
winds with a fresh snow pack will promote a rather chilly Sunday
night with lows potentially at or below zero across interior
northern Illinois. Very cold conditions will persist through
Tuesday as a reinforcing shot of colder air arrives on Monday.

A mid-level wave crossing the Ohio River Valley late Monday
afternoon and Monday night is now exhibiting decent phasing with
a sub-tropical system over the Lower Mississippi River Valley,
which supports increasing chances for light accumulating snow to
affect at least the southern CWA during this time. Resultant
higher cloud cover would ultimately tamper very cold conditions
Monday night, but if there is any clearing, sub-zero lows will
again be possible.

Deep troughing now anchored over eastern Canada will lead to
colder conditions through the remainder of the week, with some
energy from a Pacific NW trough bringing another period of
potential snow to the western Great Lakes Wednesday into
Thursday.

Kluber

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1126 AM CST Fri Nov 28 2025

- Snow overspreads the region late tonight/early Saturday
  morning.

- Cigs/vsbys will steadily deteriorate through the morning.
  Periodic dips to LIFR/VLIFR anticipated, particularly midday
  Saturday onward.

- Snowfall rates generally around one half inch per hour, but
  expected to peak near 1 inch/hour Saturday afternoon. Bulk of
  snow accumulations expected from about 1 pm to 8 pm.

Northwesterly winds will turn southerly this evening and
eventually southeasterly tonight. Generally VFR conditions are
expected today, with some patches of high-MVFR strato-cu
developing.

Snow will overspread the terminals late tonight into early
Saturday morning. Some uncertainty regarding the exact start
time of light snow remains, but snow will gradually fill in and
become steady through the morning hours with widespread IFR
vsbys expected. Snowfall intensity is expected to peak Saturday
afternoon, and this is the period most likely to result in
LIFR/VLIFR conditions--at least on a temporary basis. The bulk
of snowfall accumulations are expected during the roughly
12pm-8pm timeframe, with snowfall rates intermittently nearing 1
inch per hour during this period.

Southeasterly winds will also gradually increase through the
day, with gusts increasing towards 25 kts during the afternoon.

Finally, just beyond the end of the current TAF periods: a mid-
level dryslot is expected to quickly work its way northward
Saturday evening. Temperatures will also begin to slowly warm,
and this combination may result in snow mixing with or even
changing to drizzle Saturday evening. This appears to be a lower
potential at RFD, and locally greater potential at GYY and MDW.

Carlaw

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Storm Warning from 3 AM Saturday to 6 AM CST Sunday for
     ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
     ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ103-ILZ104-
     ILZ105-ILZ106-ILZ107-ILZ108.

     Winter Storm Warning from 3 AM Saturday to midnight CST
     Saturday night for ILZ033-ILZ039.

IN...Winter Storm Warning from 3 AM Saturday to 6 AM CST Sunday for
     INZ001-INZ002.

     Winter Storm Warning from 3 AM CST /4 AM EST/ Saturday to
     midnight CST /1 AM EST/ Saturday night for INZ010-INZ011-
     INZ019.

LM...Small Craft Advisory until 3 PM CST this afternoon for the IN
     nearshore waters.

&&

$$

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