523
FXUS63 KIWX 092354
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
654 PM EST Sun Nov 9 2025

.KEY MESSAGES...

- Multiple rounds of lake effect snow are expected through early
  Tuesday. Winter Storm Warnings and Winter Weather Advisories
  are in effect until 1 AM EST Tuesday downwind of Lake
  Michigan.

- The heaviest snow is expected from 6 PM to 1 AM EST tonight
  where snowfall amounts should be 4-8"+ within the Winter
  Storm Warning area.

- Expect slick, snow covered roads along the I-94 and I-80/I-90
  corridors tonight!

- Snow showers are also expected away from the lake late tonight
  into early Monday with 1-2" possible.

- After a lull in lake effect snow Monday morning, additional
  accumulations are expected Monday afternoon and evening.

- Near record cold high temperatures possible Monday. Breezy
  northwest winds will make for wind chills only in the teens
  and 20s.

&&

.DISCUSSION...
Issued at 213 PM EST Sun Nov 9 2025

On the backside of the low pressure system centered over the Ohio
River Valley, breezy north winds have allowed for lake effect snow
to develop. Several rounds of lake effect snow are likely from this
afternoon/evening through early Tuesday morning. Currently, a
single, dominant, N-S oriented lake effect snow band is located
across La Porte, Starke, and Pulaski counties in Indiana. The
band extends down the long axis of Lake Michigan due to the
elongated northerly fetch extending all the way up to Lake
Superior. The lake effect snow band initially began this morning
over Gary and Chesterton, IN and has now pivoted eastward
through NW Indiana and should continue up towards St Joseph, MI
as low level converging winds take on a more north- northwest
component this afternoon and evening. Winter Storm Warnings and
Winter Weather Advisories are in effect until 1 AM EST Tuesday
downwind of Lake Michigan. With daytime temperatures above
freezing and highly variable snowfall rates within the band,
accumulations will range from 1-4" through the afternoon, with
locally higher amounts possible in La Porte County, IN.
Depending on how far inland the lake effect snow band gets this
afternoon and evening, snow showers will be possible as far east
as I-69 and as far south as the I-70 corridor. Visibilities
will be highly variable and could be as low as 1/4 mile within
the heaviest part of the lake effect snow band. If any heavier
snow rates do materialize (2"+ per hour), there could be
accumulations on roads, especially within the primary NW Indiana
and SW Lower Michigan snowbelts along the I-94 corridor.

Lake effect snow continues overnight into early Monday morning and
the environment will become incredibly favorable, with increasing
inversion heights to around 15,000 ft and impressively steep low
level lapse rates of 8.5-9 C/km. Near record cold 500 mb temps
around -40C combined with Lake Michigan water temperatures between
10C-12C will create 500-1000 J/kg of lake-induced CAPE and potential
for thundersnow. The lake effect snow band will be capable of
producing snowfall rates of up to 2-3"/hour this evening and early
overnight, with the heaviest snow likely from 6 PM to 1 AM EST. In
the Warning area, snowfall amounts of 4-6"+ are expected across
portions of La Porte, St Joseph [IN], and Berrien counties. Locally
higher amounts of 8"+ are possible in northwest La Porte County. In
the Advisory area, snowfall amounts of 2-4" are expected. Snowfall
amounts could be highly variable across short distances due to the
unpredictability of mesovortices within the band. Surface low
temperatures drop into the upper 20s by midnight, which will
limit melting and may result in some slick, icy patches on
untreated roadways for the Monday morning commute. Travel
impacts are most likely along the I-94 and I-80/I-90 corridors,
especially this evening/tonight. Be prepared for slick, snow
covered roads!

Overnight, between 1 AM to 4 AM EST Monday, a mesolow should form
over Lake Michigan and drop due south over the lake, which will pull
the axis of the lake effect snow to the west over the Chicago metro.
By 4 AM EST Monday, the lake effect snow band will be completely
west of the forecast area. Aided by lake effect snow and additional
moisture coming off of Lake Huron, as the mesolow comes through,
minor snow accumulations of 1" (maybe isolated 2") will also be
possible overnight in NW Ohio and northern Indiana. With NNE
flow, the Chicago metro area will likely receive the brunt of
the heavy lake effect snow and travel impacts around the time of
the Monday morning commute, where a potentially historic event
could unfold. Meanwhile, our forecast area will see a lull in
lake effect snow until late morning/early afternoon Monday. Lake
effect snow pivots back into NW Indiana and SW Lower Michigan
during the day Monday as winds shift from NNE to NW. Strongly
negative theta-e lapse rates will allow for snow to extend
further inland, especially late Monday into early Tuesday north
of US 30. A few hours of 1-2"/hour rates will be possible Monday
afternoon through early Tuesday, resulting in 2-4" of
accumulations across the typical snowbelts to as far southeast
as the Fort Wayne area. The Monday evening commute and Tuesday
morning commute may be impacted depending on where and when the
heaviest snow falls.

Breezy northwest winds and strong CAA will keep temperatures around
20 degrees below normal for this time of year on Monday. High
temperatures will be in the low to mid 30s, with some locations
struggling to get above freezing. When factoring in the winds, wind
chills will only be in the teens and 20s all day Monday.

Through the rest of the week, temperatures gradually warm and return
to near normal by Friday and Saturday. Quiet and dry weather resumes
Wednesday through the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 639 PM EST Sun Nov 9 2025

The main LES bands associated with a mesolow moving southward
over southern Lake Michigan will create the highest impacts
tonight into early Monday morning. Occasional IFR/LIFR
conditions are possible in the heavier lake effect snow showers
this evening for KSBN. KFWA may see some reductions to MVFR cats
for cigs and vsby in a few bands of snow showers that make it
southeastward to that TAF site over the next several hours. A
lull in lake effect snow showers is expected after 12z Monday
when the main band becomes displaced to the west into far NW IN
and NE IL. After 19z Mon the expectation is that we will see
this aforementioned band to the west begin to shift again
eastward into the end of this TAF period and continue Monday
night as it moves eastward.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory until 1 AM EST Tuesday for INZ005-013-
     015-116-216.
     Winter Storm Warning until 1 AM EST /midnight CST/ Tuesday for
     INZ012-014-103-104-203-204.
OH...None.
MI...Winter Weather Advisory until 1 AM EST Tuesday for MIZ078.
     Winter Storm Warning until 1 AM EST Tuesday for MIZ177-277.
MARINE...Small Craft Advisory until 7 AM EST Tuesday for LMZ043-046.

&&

$$

DISCUSSION...Johnson
AVIATION...Andersen