502
FXUS63 KIWX 022315
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
615 PM EST Tue Dec 2 2025

.KEY MESSAGES...

- 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 236 PM EST Tue Dec 2 2025

High pressure takes over this afternoon behind a departing trough
and warming return flow takes over on the back side of the high
after 6z. There is some question about how much the clouds are able
to break up this evening, but given the extent of the fog we`ve had
the last couple of mornings, perhaps helped along by the moisture
from wet roadways trapped under a forming inversion, could see some
fog by the morning. Aviation guidance seems to point to fog in areas
north of US-24, but that has also slackened back on the intensity
since the morning runs. One issue with the possibility of
evening/overnight fog formation is that boundary layer winds could
stay just strong enough to restrict it to more of a stratus deck.
Have handled this with some patchy fog. One other piece of note is
the possibility for some seeder feeder freezing drizzle as high
clouds overtop the low level moisture with the lift approaching and
temperatures staying below freezing tonight. There`s not too much
confidence in this though as most of those parcel trajectories
traverse Lake MI so will just discuss the chance here.

Then, as a shortwave rounds the base of the trough associated with
the upper low in Central Canada, a cold front pushes southeastward
for Wednesday. As the area of convergence slides down the eastern
side of Lake MI, wouldn`t be surprised to see some lake enhancement
with over 50 J/kg of SBCAPE and -2 theta-e lapse rates, and low
level winds obtaining more of a northerly component approaching
Berrien county by 21z. Lake induced inversions are marginal,
reaching around 1.5 km and delta Ts reach around 15 C at most. This
keeps the omega below the DGZ until around 00z as the cold air
begins to arrive on NW winds. The lake induced CAPE values drop
between 00 and 06z and low level moisture also begins to drop during
that time. It`s also pretty nearly a dry DGZ for a short time, so
wouldn`t be surprised to see some freezing drizzle mix in here and
there. Have kept this out of the forecast for now, though due to low
confidence in its possibility. The other limiting factor for lake
enhanced snow is that the main vort max passes by to the north of
the area as opposed to moving through the tear drop of Lake MI so
forcing is not conducive.

Following the cold front, a 1035 mb high pressure system dives
southeast from the Northern Plains into the Mississippi Valley and
Lower Great Lakes regions for Thursday and Thursday night. As such,
850 mb temps fall to -10C to -15C by 12z Thursday. As this swings
into the area, the gradient increases which helps increase winds.
Bufkit soundings/ momentum transfer indicate a period of 15 to 25
mph wind gusts may occur and this could allow for cold weather
advisory conditions overnight. Those relax quickly Thursday morning
so it`ll be interesting to see if there`s some overlap at all
between the arriving cold air and the lingering wind gusts. The
other factor would be if there`s any lingering new snow from the
Wednesday front that could enhance radiational cooling to take temps
lower should winds end up weaker. Highs on Thursday struggle to get
out of the 20s and lows Thursday night drop towards either side of 0
degrees.

The core of the cold swings through on Thursday pretty quickly and
is already moving away before the worst of the cold Thursday night.
The back side of the high is already providing warming return flow
Thursday night through Friday night, which is when we expect the
coldest temperatures to be. Friday stays securely in the low 20s and
lows Friday night are already back towards the mid teens.

Friday through Saturday, some weak shortwaves move through in the
flow, but a mix of sun and clouds should be the main story as
suppression and subsidence keep precip at bay. We`ll have to
look forward to later this weekend for our next system.
Discrepancies in their storm track and wave handling create
model output differences. However, it does appear cold enough to
produce snow.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 615 PM EST Tue Dec 2 2025

Difficult aviation forecast tonight with a thin layer of low
stratus that models are struggling to resolve and potential for
fog if the stratus does scatter out. For now, observational
trends suggest stratus will hold firm through the night so will
keep that going longer and limit any fog mention. However,
confidence is not high and adjustments may be needed. Low
confidence on exact ceiling heights as well given most locations
currently below 1 kft but most guidance suggesting ceilings
around 2 kft. Some brief VFR possible at KFWA Wed morning but
KSBN will likely remain under low stratus. More light snow
likely late Wed afternoon as a strong cold front approaches the
region.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 1 AM Wednesday to 7 PM EST Thursday
     for LMZ043-046.

&&

$$

DISCUSSION...Roller
AVIATION...AGD