834
FXUS63 KLOT 301146
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
546 AM CST Sun Nov 30 2025

.KEY MESSAGES...

- Winter weather advisory is in effect through noon today for
  areas along and north of I-80 for additional light snow with
  wind gusts 30-35 mph potentially causing blowing snow.

- Accumulating snow to impact the Monday afternoon and evening
  commute and result in hazardous travel conditions.

- Well below normal temperatures will persist through next
  weekend with wind chills -5 to -15 possible Thursday and
  Friday mornings.

&&

.DISCUSSION...
Issued at 255 AM CST Sun Nov 30 2025

Short term challenge is how to handle headlines. Periods of
light snow will continue across northern IL and into northwest
IN through late morning and as temperatures cool, the snow will
become lighter/fluffy. Westerly winds will be gusting into the
30-35 mph range with some higher gusts possible this morning.
These conditions will result in some travel impacts but no
longer expecting warning level impacts and opted to replace the
winter storm warning with a winter weather advisory until noon
today for roughly areas along and north of I-80. Additional/new
snowfall from this point until it ends this morning will likely
be no more than one inch, with some areas possibly only seeing a
dusting of new snow accumulation. There remains uncertainty for
how long any lake effect snow may persist into Porter County
and the advisory may need to be extended there, but for now
opted to maintain the same expiration time of noon/18z. There
will remain a chance of flurries this afternoon.

With the new snow pack and light winds tonight, low temps could
really tank but there remains uncertainty for cloud cover with
both slowly eroding lower clouds and then increasing high/mid
clouds by daybreak Monday morning. Lows in the single digits
across northwest IL to lower/mid teens elsewhere look ok for
now, but changes may be needed based on cloud trends.

Attention then turns to the next accumulating snow that
continues to speed up, now arriving during early/mid Monday
afternoon. Ensemble support/agreement has steadily increased
over the past 24-48 hours and blended pops have steadily
climbed. Made additional upward changes to pops for Monday
afternoon/evening with this snow now looking to start just
before the Monday afternoon commute begins. With expected
cloudy skies on Monday, high temps may only climb into the 20s
allowing the snow to begin to stick when it begins falling. Qpf
amounts in the 0.2 inch to maybe 0.25 inch range with snow
ratios perhaps averaging 15:1 would yield 2-4 inches. While this
is on the low side of an advisory, with it falling during rush
hour, an advisory will need to be considered with later
forecasts for this time period. The snow will be ending from
west to east early Tuesday morning but with temperatures falling
back into the teens, any untreated surfaces will likely still
be slippery with at least some travel concerns for the Tuesday
morning rush hour.

A cold front is expected to move across the region Wednesday
with a chance of snow along/ahead of this cold front. Its
possible the snow may develop right over the cwa and timing
could also be for the Wednesday afternoon/evening commute.
Still quite a bit of uncertainty for this time period. High
pressure would then move across the area Thursday with the
potential for some very cold temps both Thursday and Friday
mornings, possibly subzero for at least parts of the area. Winds
might still be in the 5-10 mph range both mornings with the
lowest winds during the day Thursday, resulting in morning wind
chills both mornings possibly in the -5 to -15 range.

Still several days away, but will need to continue to monitor
another possible accumulating snow for Friday afternoon/evening
as there is growing ensemble support for this time period. cms

&&

.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 546 AM CST Sun Nov 30 2025

Key Aviation Forecast Messages:

- Lingering light snow this morning, with intermittent IFR
  conditions. Period of slightly more intense light snow and
  solid IFR potential 12-16Z, with some minor accumulation
  potential.

- MVFR stratus lingers through this afternoon, but may persist
  overnight especially south/west of terminals.

- Strong W-WNW winds gusting near 30 kts this morning, gradually
  easing this afternoon.

Surface low pressure associated with our winter storm was over
central lower MI early this morning, pulling away from the area
to the northeast. A secondary cold front trails across far
southern WI however, and will push southeast across the
terminals this morning. This will be accompanied by a band of
somewhat more intense snow for a few hour period roughly between
12-16Z, with associated IFR vis/cigs (potentially brief LIFR
vis) and some additional minor accumulations of up to 1 inch.
Light snow should then end late this morning though can`t rule
out a few stray flakes/flurries from the stratus deck with no
vis impacts or accumulation into this afternoon. MVFR stratus
will linger through the afternoon and should scatter out by
evening, though may persist not too far tot the south and west
of the terminals.

Surface high pressure builds across the area late tonight, with
a period of light/variable winds after midnight turning light
southwest Monday morning. Some guidance develops fog predawn
within the surface ridge, though high/mid clouds quickly build
back into the area early Monday morning, making for lower
confidence in any fog development at this time. Mid clouds
thicken Monday in advance of the next weather system which will
bring snow back to the terminals by Monday afternoon, just
beyond the end of the current 30 hour ORD/MDW forecasts.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory until noon CST today for ILZ003-ILZ004-
     ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ020-
     ILZ103-ILZ104-ILZ105-ILZ106-ILZ108.

IN...Winter Weather Advisory until noon CST today for INZ001-INZ002.

LM...Small Craft Advisory until 10 PM CST this evening for the IL
     nearshore waters.

     Small Craft Advisory until 7 AM CST Monday for the IN
     nearshore waters.

&&

$$

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