912
FXUS63 KIWX 011652
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1252 PM EDT Mon Sep 1 2025

.KEY MESSAGES...

- Seasonable and dry today through Wednesday afternoon.

- Big changes are ahead by midweek! A strong cold front will
  sweep through Wednesday evening through early Thursday,
  bringing chances for rain/storms and much cooler temperatures.

- Highs only in the 60s Thursday then slightly warmer in the
  low 70s on Friday. Cooler than normal temperatures continue
  through the weekend.

- There is a High Swim Risk for southeast Lake Michigan beaches on
  Thursday.

&&

.DISCUSSION...
Issued at 242 AM EDT Mon Sep 1 2025

Happy Labor Day and happy start to meteorological Fall! With
expansive surface high pressure over the Great Lakes and
Northeast regions, expect dry conditions to continue through
Wednesday afternoon. Given antecedent dry conditions, diurnal
temperature spreads will be around 30-35 degrees again today.
Mostly clear skies and comfortable humidity are on tap, with
high temperatures climbing up into the upper 70s to near 80
degrees by the afternoon. Lows will be slightly more mild
Tuesday morning in the low 50s.

Big changes are ahead by midweek! Get your sweaters, flannels, and
pumpkin spice lattes ready for Thursday! High temperatures will drop
from the low 80s on Wednesday to the mid to upper 60s by Thursday.
An upper level trough will drive a surface cold front through the
forecast area on Wednesday evening through Thursday morning. There
are chances for rain and maybe even an embedded thunderstorm or two
late Wednesday afternoon through early Thursday morning. There will
be increased moisture out ahead of the front (dewpoints in the low
60s) although much of Wednesday afternoon should be dry because of
the lack of forcing until the front and upper level trough arrive.
The best chances for rain/storms will be after sunset Wednesday
through daybreak Thursday, with rain totals up to 0.50" to 0.75" per
NBM and WPC QPF guidance. A tight pressure gradient sets up along
and behind the front, so expect gusty winds to accompany the sharp
temperature drop and rain late Wednesday into Thursday. Severe
weather is not expected. With persistent northwest flow and strong
CAA on Thursday, temperatures will only make it to the mid to upper
60s for highs! A dry continental Canadian airmass settles over the
Midwest and Great Lakes behind the front, allowing for lows well
into the 40s on Friday morning (with maybe a few low lying, rural
locations making it into the upper 30s? Very low confidence but
something we`ll have to keep an eye on.)

Behind the strong cold front, breezy northwest winds and high waves
will develop over Lake Michigan late Wednesday into the day on
Thursday. There is a High Swim Risk for Berrien County, MI and
La Porte County, IN beaches on Thursday. 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 as
well.

Winds shift from the northwest to southwest on Friday, with breezy
conditions and some WAA boosting temperatures up into the upper 60s
to low 70s on Friday (a few degrees warmer than previously forecast)
A secondary cold front will sweep through on Friday with low chances
for rain. This second cold front will reinstate northwest flow and
reinforce cooler than normal temperatures for the weekend. Have kept
with the NBM for now in the long range, which has highs in the low
70s area-wide over the weekend. The GFS and ECMWF have both caught
onto this secondary cold front and also have cooler than normal
temperatures persisting into early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1252 PM EDT Mon Sep 1 2025

Rex block pattern continues a forecast persistence mode with the 18Z
TAFs. An expansive low level anticyclone tied to a broad northern
stream upper ridge will continue to allow a weak easterly flow
regime to persist across northern Indiana. With a few degrees of
warming today compared to yesterday, some potential exists for a
weak lake breeze to impact KSBN late in the afternoon or early
evening with a brief period of northeast winds less than 10 knots
possible. Some patchy shallow fog is also possible early Tuesday
morning, but expectation is that this would be mainly for outlying
rural locations and will continue to omit mention from terminal
forecast.

&&

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

&&

$$

DISCUSSION...Johnson
AVIATION...Marsili