487
FXUS63 KIWX 031042
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
642 AM EDT Wed Sep 3 2025

.KEY MESSAGES...

- Rain likely late this afternoon through early Thursday
  morning, with heavy rain and isolated thunderstorms possible
  at times. Rain totals are expected to be between 0.5" to 1".

- Highs near 80 today then turning sharply cooler on Thursday
  with highs only in the 60s.

- Highs only in the 60s to around 70 are expected Thursday
  through Saturday. Briefly warmer on Friday south of US 24 in
  the low 70s, then cooler and dry area-wide for the upcoming
  weekend.

- There is a High Swim Risk for southern Lake Michigan beaches
  in La Porte, IN and Berrien County, MI on Thursday. Hazardous
  swimming conditions persist into Friday and Saturday as well.

&&

.DISCUSSION...
Issued at 241 AM EDT Wed Sep 3 2025

A strong surface cold front is currently located to our
northwest across northern Wisconsin, Minnesota, and South
Dakota. This cold front and the associated upper level trough
will continue southeast through the Midwest and Great Lakes
regions today through Thursday. In our forecast area, the
morning and afternoon hours will be dry today, but the
aforementioned cold front will bring 60-90% chances for rain
starting late in the afternoon in our far northwest. The cold
front will move from the northwest to southeast, bringing
increasing rain chances to the area this evening and into the
overnight hours. A few embedded thunderstorms will also be
possible given ~500 J/kg of surface instability. Rain will come
to an end early Thursday with a few showers lingering south of
the US 24 corridor through daybreak. PWAT values will be around
the 75th percentile of normal and with a strong source of lift
provided by the cold front, a much needed soaking rainfall is
possible for much of the area. Forecast soundings continue to
depict tall, skinny CAPE profiles, a deep warm cloud layer, and
a very saturated profile. Latest model guidance from the HRRR,
HREF, NAM, NAMNest and RAP all show a bullseye somewhere over
our forecast area of 1"+ of rain but there is still uncertainty
as to exactly where. Rain may be more scattered initially near
Lake Michigan this afternoon and evening before becoming more
widespread along and east of I-69 and south of US 24 after
sunset where the better environment exists for heavy rain. At
this time, I am maintaining the previous forecast that 0.50" of
rain is likely area-wide but I would not be surprised to see
totals that approach or even exceed 1", especially south of US
24 or along and east of I-69. Severe weather is not expected,
however, gusty winds of up to 20 to 30 MPH will likely accompany
the cold front this afternoon and evening.

Strong CAA and northwest flow on Thursday will usher in much cooler
temperatures post-front. A cool Canadian airmass will overspread
much of the Midwest and Great Lakes regions with cooler than normal
temperatures. Highs Thursday will be only in the mid to upper 60s
area-wide, which is about 10 degrees below normal for this time of
year. Overnight lows Thursday into Friday will fall into the mid to
upper 40s

Winds will shift from the northwest to southwest late Thursday into
the day on Friday, with breezy conditions and WAA boosting
temperatures up into the low to mid 70s along and south of US 24. A
secondary cold front will sweep through on Friday. A few scattered
showers are possible near Lake Michigan but much of the area will
stay dry or only see a few sprinkles. This second cold front will
reinstate northwest flow and reinforce cooler than normal
temperatures for the weekend. Highs look to only reach the upper 60s
to around 70 degrees both days. Mid to long range model guidance has
trended towards cooler than normal temperatures persisting into
early next week as surface high builds across the region.
Temperatures will gradually moderate back towards seasonable levels
next week.

Additionally, breezy northwest winds on Thursday will generate high
waves over Lake Michigan. Waves will start to increase after sunset
on Wednesday; the strong cold front may create
seiche/meteotsunami activity across southern Lake Michigan that
could intensify wave development. A Beach Hazards Statement
will go into effect from 8 PM ET/7 PM CT tonight through 5 PM
ET/4 PM CT Thursday. There is a High Swim Risk for both Berrien
County, MI and La Porte County, IN beaches on Thursday with
waves expected in the 4 to 6 feet range. Stay out of the water
and stay off of piers/breakwalls! Strong rip and structural
currents are expected in addition to the high wave action.
Hazardous swimming conditions likely persist into Friday and
maybe even Saturday as well where additional headlines may be
needed.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 639 AM EDT Wed Sep 3 2025

Cold front will sweep through this afternoon and evening,
bringing gusty winds ahead of it and a period of showers (few
storms) along and behind it. Most favorable time frame continues
to be roughly 21Z-3Z at KSBN and 00-09Z at KFWA. Periods of MVFR
cigs and vsbys are expected during the peak of the event.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement from this evening through Thursday
     afternoon for INZ103.
OH...None.
MI...Beach Hazards Statement from this evening through Thursday
     afternoon for MIZ177-277.
MARINE...Small Craft Advisory from 8 PM this evening to 5 PM EDT
     Thursday for LMZ043-046.

&&

$$

DISCUSSION...Johnson
AVIATION...Fisher