624
FXUS63 KIWX 221009
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
609 AM EDT Fri Aug 22 2025

.KEY MESSAGES...

- Patchy fog early this morning.

- There are low chances (10-30%) for showers Saturday afternoon.
  Scattered lake effect showers likely on Monday.

- Significantly cooler than normal temperatures Sunday through
  Tuesday.

- Dangerous swimming conditions for southeast Lake Michigan beaches
possible Sunday into Monday.

&&

.DISCUSSION...
Issued at 252 AM EDT Fri Aug 22 2025

Given the dry and comfortable airmass over the region this morning
combined with residual ground moisture from recent rainfall, areas
of patchy fog are possible this morning. Patchy fog will likely
develop between 5 AM to 9 AM ET this morning before dissipating.
Today, another pleasant August day is ahead with highs near 80
degrees, intermittent sunshine, and comfortable humidity
levels. Winds will still be from the northeast, which will help
keep some lake effect cloud cover off of Lake Erie over the
area, especially over northwest Ohio and northeast Indiana.

The next chance for rain/storms arrives during the day on Saturday.
A large area of low pressure will spin and develop over Ontario,
with the system`s attendant cold front expected to move through much
of the eastern CONUS. This front looks to come through our forecast
area during the afternoon and evening hours on Saturday, bringing
low chances (10-30%) for showers and storms. With uncertainties
still on how much moisture and forcing will accompany this front,
have kept PoPs low.

Behind this front, strong CAA will push a refreshing,
substantially cooler airmass across much of the Midwest and
Great Lakes. With cold air moving over the relatively warm
waters of Lake Michigan, expect lake effect clouds and showers
late Sunday into the day on Monday and again potentially on
Tuesday. Sunday`s chances may be limited depending on how much
dry air is aloft. Soundings near Lake Michigan depict a
favorable environment for diurnally-driven lake effect showers
on Monday with low level convergence along a trough that pivots
through, cyclonic flow, and tall inversion heights of 7-8 km.
Can`t rule out potential for waterspouts over southern Lake
Michigan as well, especially if the low level convergence sets
up over the lake. Temperatures on Monday and Tuesday will
struggle to reach the low 70s for highs, especially in areas
closer to Lake Michigan where lake effect cloud cover remains.
Meanwhile, particularly away from the lake, nights will be crisp
with near- record lows in the mid to upper 40s!

As a large area of surface high pressure builds across the central
CONUS midweek, expect dry conditions to persist through much of the
week. Temperatures will slowly rebound towards more seasonable
levels by the weekend (with highs near 80 degrees).

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 607 AM EDT Fri Aug 22 2025

Patchy fog, dense at times, will come and go over the next
couple hours. Coverage has been variable which squashes forecast
confidence with respect to timing of FM groups. Increasing cloud
cover late in the TAF period, especially at KSBN, should limit
the overall fog concern for the coming night. Light wind
otherwise today beneath high pressure.

&&

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

&&

$$

DISCUSSION...Johnson
AVIATION...Brown