Portage, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

404
FXUS63 KIWX 232342
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
642 PM EST Tue Dec 23 2025

.KEY MESSAGES...
- Patchy fog late tonight with lows near 30.

- Rain, and even freezing rain for south central Michigan, is
  expected Wednesday night and Thursday night. Rain lingers
  Friday morning.

- Mild through the rest of this week with highs in the 40s and
  50s. Colder by Sunday and Monday.

&&

.DISCUSSION...
Issued at 213 PM EST Tue Dec 23 2025

Northern Indiana will be the battleground for clashing air masses
these next couple of days as warm fronts come and go. Temperatures
will generally be above normal with chances for rain and even
freezing rain.

Stratus and fog are gradually mixing out this afternoon as cooler
and drier air attempts to seep in from the northwest. Aloft, 850-mb
temperature advection is neutral and surface high pressure nosing in
will create an inversion that will trap any lingering low-level
moisture leading to at least patchy fog overnight. Northwest IN and
southwest MI may be spared with their dew points already in the
upper-30s as of this midday writing. Cloud cover is another
variable that muddies the forecast a bit. Duration of fog
appears to be limited to pre-dawn hours (~3-4 hours) which will
help reduce travel issues from freezing fog. Confidence is low
on the duration and coverage of fog, but enough ingredients are
in place to afford the "patchy fog" mention.

Warm air advection resumes Wednesday as surface high pressure tracks
east and poleward moisture transport occurs on the western fringe of
a Gulf Coast ridge. Weak low pressure by Wednesday night will result
in a chance of rain, and even freezing rain in southern MI. The
source region (mid-Mississippi Valley) for this rain chance is much
better than this morning`s which was polar (i.e., dry) in nature. A
majority of the forecast area will experience rain, but forecast
soundings in southern MI depict a stout low-level warm nose
indicative of a freezing rain risk. Luckily, low temperatures are
forecast to be right near freezing (as opposed to well into the 20s,
for example) which may limit overall impacts. Instead, a greater
likelihood of freezing rain exists Thursday night into early Friday
morning when low temperatures will be in the upper-20s for far south-
central Michigan spreading into far northwest Ohio.

Colder with rain changing to lake effect snow Sunday as a low moves
across the upper Great Lakes. This replaces late-week high
temperatures that were in the 50s to highs near 40 Sunday (in the
west and north) followed by highs in the 20s by Monday.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 640 PM EST Tue Dec 23 2025

High level clouds continue to stream through a broad, low
amplitude upstream upper level ridge this evening. Surface high
pressure will seep into the Great Lakes tonight allowing the
initial west-northwest winds of 5 to 10 knots to become light
and variable overnight. Partly cloudy skies and light winds
should allow for good radiational cooling and patchy fog
concerns with lows temps well below the crossover temps.
Confidence in extent of vsby restrictions is still on the low
side as low level dry air advection will be relatively strong.
At this time have maintained idea of MVFR vsbys overnight into
early Wednesday, although cannot completely rule out some IFR
vsbys in the 08Z-12Z window. Southeast winds develop during the
day Friday as the low level anticyclone shifts off to the east.
Conditions are expected to deteriorate back to MVFR and then to
IFR Wednesday evening and overnight respectively, but this is
well beyond this forecast valid period.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Brown
AVIATION...Marsili