039
FXUS63 KIWX 211815
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
215 PM EDT Fri Aug 21 2026

.KEY MESSAGES...

- Isolated showers and storms possible east of I-69 this
  afternoon and evening.

- 30-60% chances for scattered rain and storms arrive tonight through
  Saturday. An isolated strong storm capable of gusty winds and
  brief heavy rain is possible west of US-31 this evening and
  east of I-69 Saturday afternoon.

- Dangerous swimming conditions expected for southeast Lake
  Michigan beaches on Saturday and Sunday with High Swim risks
  both days. Northwest winds will gust to 30 mph with waves of 3
  to 5 feet.

- Dry weather returns Sunday and Monday with below normal
  temperatures and low humidity.

&&

.DISCUSSION...
Issued at 132 PM EDT Fri Aug 21 2026

An upper level low over the Hudson Bay will be the focus of the
forecast for the next 36-48 hours, as the attendant cold front with
this system sweeps through our area and brings periodic chances for
rain and storms tonight through early Sunday. Mainly dry conditions
are expected to continue this afternoon, however, isolated
showers and storms remain possible through sunset east of I-69
with a leading 500 mb shortwave associated with the upper level
low. Scattered cumulus development is already noted on visible
satellite imagery this afternoon. Isolated showers are also
likely in the vicinity of Lake Michigan this afternoon where a
dying convection complex from upstream is moving in. Into this
evening, with the cold front still back in Wisconsin and the
upper level trough expected to begin to dig into the Great
Lakes, we will have to watch what additional development there
is upstream over southern Wisconsin and northern Illinois. CAMs
are in fairly good agreement in a cluster of storms developing
this evening to our northwest and diving southeast after sunset.
Given that shear and instability will wane after sunset, these
storms should be diminishing by the time they reach northwest
and north central Indiana tonight. Can`t rule out an isolated
gusty storm or two but not expecting much if any severe threat.
Locations along and east of I-69 will remain dry until daybreak
Saturday.

Showers gradually become more numerous as the front pushes eastward
and as the upper level trough amplifies during the morning and early
afternoon hours on Saturday. Have maintained PoPs between 30-60% on
Saturday, with the highest chances in northwest Ohio. With the front
expected to come through between the morning and early afternoon
hours, this is not the most favorable diurnal timeframe for storms.
Again, can`t rule out an isolated strong storm or two (especially in
northwest Ohio) as a corridor of up to 1500 MLCAPE could develop
east of I-69, but the likelihood of organized severe weather
tomorrow is low given marginal shear of 20-30 kts and poor low/mid
level lapse rates. With a tightening pressure gradient and strong
cyclonic flow on the backside of the departing front on Saturday
evening, I wouldn`t be surprised if widely scattered lake effect
showers develop downwind of Lake Michigan for several hours late
Saturday into early Sunday. Winds will be breezy out of the
northwest through the remainder of the weekend with northwest winds
gusting as high as 25 to 30 mph.

The aforementioned frontal passage is expected to stir up southern
Lake Michigan, generating large waves and dangerous currents
throughout the weekend. Northwest, onshore flow with northwest winds
gusting to 30 mph will allow for waves to build to 3 to 5 feet with
strong currents expected. High Swim Risks will be in place both days
this weekend. Beach Hazards Statements will need to be issued this
afternoon for Berrien and La Porte counties at least for Saturday.
There will be a lull in winds and possibly waves overnight before
dangerous conditions ramp up again into Sunday, with additional
headlines likely needed. Heed beach flags/lifeguards and stay
out of the water!

High pressure builds into the Great Lakes and Midwest regions again
by Sunday, giving us the first taste of fall as temperatures and
dewpoints fall to comfortable levels. Temperatures will be slightly
below normal on Sunday and Monday with highs in the low to mid 70s
with northwest flow behind the cold frontal passage. A few crisp
nights are ahead Sunday night and Monday night with lows in the low
to mid 50s. With much drier air building in, dewpoints only in the
50s will make for several nice days! Another cold front moves in
Wednesday with low chances (20-30%) for rain/storms maintained.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 137 PM EDT Fri Aug 21 2026

Mainly VFR conditions expected through at least 05z Sat for
both TAF sites. There is a possibility of an isolated
shower/storm for KFWA later this afternoon however, confidence
is pretty low on this occurrence so did leave mention out of the
TAF. After 05z a frontal passage pushing northwest to southeast
will increase chances for scattered showers and thunderstorms
bringing periods of MVFR vsbys/cigs for both TAF sites. KSBN
will see conditions begin to improve first by late morning after
15z Sat with scattered showers possible for KFWA through the
remainder of this TAF period after 13z Sat.

&&

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

&&

$$

DISCUSSION...Johnson
AVIATION...Andersen