860
FXUS63 KIWX 020900
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
400 AM EST Tue Dec 2 2025

.KEY MESSAGES...

- Snow diminishes early this morning from west to east. Some
  lake effect snow showers through early afternoon, but
  additional snow accumulations should be generally less than an
  inch.

- Patchy fog is expected across northwest Indiana this morning,
  the fog may be locally dense.

- A strong cold front pushes across the area on Wednesday and
  will likely be accompanied by some light snow accumulations
  of around an inch.

- Much colder air moves in for middle of the week with lows near
  0 by Thursday night and wind chills as cold as 10 below. Some
  moderation in temperatures for the weekend, but still below
  normal.

&&

.DISCUSSION...
Issued at 352 AM EST Tue Dec 2 2025

Bands of snow continue this morning as a positively tilted
upper level trough tracks across the area. The forcing with this
system is highly elevated in nature with 700-500 mb fgen
forcing a primary driver. Since 06Z, mesobanding became more
distinct, particularly across portions of central Indiana into
far northeast Indiana/northwest Ohio along and south of US 24.
Another localized band formed from Rochester IN to Coldwater MI,
but forcing with this mesoband was likely highly elevated with
weaker UVMs in the snow production layer. Will be interesting to
see reports trickle in this morning and would suspect at least
a few 5+ inch reports across far south central/southeast
portions of the forecast area where brief isentropic forcing
last evening was followed by repeated mesobands. Across the
remainder of the area, snow production efficiency was less than
optimal, with generally a 1 to 3 inch snowfall for most areas.
Snow should continue to taper sharply through daybreak. The
Winter Weather Advisory for NW Indiana will likely be cancelled
around 09Z, while the remainder of the Winter Weather Advisory
headlines will likely be cancelled/expired in the 11Z-12Z
window.

In the wake of the snow, some concern that patchy fog development
may be supported again across northwest Indiana, but uncertainty
exists regarding how extensive this threat would be. Cannot
rule out some localized patchy dense fog this morning generally
west of US 31. The other thing to watch this morning in wake of
system snow is the eastward migration of what has been a mid-
lake snow band over Lake Michigan. This band is now shifting
east along with the associated sfc trough. Over next several
hours, lake effect parameters become much more marginal across
the local area as subsidence behind the departing mid level wave
supports continued lowering inversion heights and drying of
DGZ. Would expect any lake effect accums this morning across the
area to be less than an inch and likely not a factor in any
advisory headline extension this morning.

For tonight center of low level anticyclone will track of the area
with return southerly flow developing overnight. Some hires guidance
is picking up on a fog potential in this setup with return flow over
fresh snowpack. If low clouds can scatter this evening,
radiative processes may help fog form initially also. However,
some potential with strong lingering low level inversion that
low clouds could linger or re-form. This appears to be a muddled
combination of radiative/advective processes over time tonight,
but have included mention of some patchy fog across most areas
this evening/overnight.

After brief warm advection shot late tonight into early Wednesday, a
strong cold front will make its way across the area on Wednesday as
broad upper PV anomaly shifts across Hudson Bay/Ontario. Strongest
upper forcing should migrate north/northeast of local area, but
glancing blow of forcing with this upper trough and modest low level
fgen forcing should support a band of snow filling in along low
level front. Moisture and duration of deep moisture will be
a limiting factor with just a narrow axis of 3 g/kg 850 mb
mixing ratios in vicinity of the front. A band of light snow
with a potential of one inch accumulations is expected across SW
Lower MI/NW IN, with expectation that frontal forcing will
become a little more washed out with southeast extent as the
upper PV anomaly shifts across southeast Canada. Some lake
response possible late Wednesday night into early Thursday but
depth of lake induced instability appears limited once again.

An expansive low level anticyclone shifts across the region Wed
night into Thu night with coldest mins of the season expected
Thursday night. Temps should rapidly drop off early Thursday evening
before likely becoming more steady late in the night. Lows around
zero look like a good chance for many areas, and potentially sub-
zero for areas with fresh snowpack from the Wednesday system.
Subtle increase in southerly winds toward daybreak Friday should
allow for some 5 to 10 degree below wind chills. Some
moderation temperatures is expected for the weekend but
remaining below normal for early December. The large scale
synoptic pattern of west coast ridging and SE Canadian troughing
could provide favorable low level baroclinicity for potential
additional systems to track across the Mid MS Valley/Great Lakes
next weekend and have maintained broadbrush chance snow PoPs
next weekend into early next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1221 AM EST Tue Dec 2 2025

Light to moderate snow will persist through the area until
9-10Z this morning. Visibilities are down as low as 1 mile in
the heavier pockets of snow. At KFWA and KSBN, IFR ceilings and
visibilities will prevail through the morning. Winds will be
light and variable, eventually becoming southwest by the
afternoon hours. There may be a few hours of light lake effect
snow in the vicinity of KSBN as winds will be northwest coming
off of Lake Michigan. The best chances for any lingering lake
effect at KSBN will be before 18Z. Even after the snow tapers
off, it will take some time for ceilings to lift. IFR to MVFR
ceilings will last through much of the afternoon and evening,
with a gradual return to VFR ceilings overnight tonight.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory until 7 AM EST /6 AM CST/ this morning
     for INZ005>009-012>015-017-018-020-022>027-032>034-103-
     104-116-203-204-216.
OH...Winter Weather Advisory until 7 AM EST this morning for OHZ001-
     002-004-005-015-016-024-025.
MI...None.
MARINE...Small Craft Advisory from 1 AM Wednesday to 7 PM EST Thursday
     for LMZ043-046.

&&

$$

DISCUSSION...Marsili
AVIATION...Johnson