629
FXUS63 KIWX 121725
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
125 PM EDT Sat Sep 12 2026

.KEY MESSAGES...

- Isolated showers and storms possible through the afternoon, mainly
  south of US 24.

- Light rain showers Sunday afternoon possible with 20-30% chances.

- Cooler Monday with highs in the 70s.

- Turning warmer and humid Tuesday and Wednesday. Additional rain
  and storm chances (40-70%) late Tuesday into Wednesday.

- There is a High swim risk forecast on Sunday for southeast
  Lake MI Beaches. Dangerous swimming conditions expected.

&&

.DISCUSSION...
Issued at 124 PM EDT Sat Sep 12 2026

Surface observations show a warm front and 500 mb shortwave draped
across northern Indiana. WAA and increased moisture transport have
allowed for scattered showers and a few storms to persist through
the morning and early afternoon, mainly along and south of US 24.
Still holding onto 20-40% chance PoPs until about 21-22Z this
afternoon as the warm front will continue lifting northeastward. An
isolated storm or two will be possible due to surface based
instability of around 1000 J/kg this afternoon. Shear and low/mid
level lapse rates will be too weak for any organized strong or
severe storms. Northwest Indiana and southwest Lower Michigan will
likely remain dry today. There is quite the contrast in sky cover on
visible satellite imagery across the area, with clear skies in the
vicinity of Lake Michigan and overcast skies mainly along and east
of I-69. Cloud cover is expected to keep highs in the low 80s today
along and south of US 24, while temperatures should climb into the
mid to maybe even upper 80s in locations that have stayed dry so far
today.

The rest of the weekend appears mainly dry except for 20-30% chances
for widely scattered showers and storms Sunday afternoon with a cold
frontal passage and associated upper level trough that passes
through the Great Lakes. Rainfall amounts should be light, less than
0.10" for most locations. Incoming high pressure behind the front
will create a tightening pressure gradient over the area, with
wind gusts up to 20-25 mph Sunday afternoon and evening. CAA
associated with northwest flow behind the front will make for a
pleasant Sunday night with lows in the upper 40s to low 50s. A
very fall-like day is ahead Monday with highs only in the low
70s.

If you have plans to head to SE Lake Michigan beaches on Sunday,
stay safe! Behind the cold frontal passage, dangerous swimming
conditions are expected for southeastern Lake Michigan beaches in
Berrien and La Porte counties. CAA and northwesterly flow Sunday
behind the front will promote onshore flow and waves of 3-5 ft,
meaning the swim risk will be High for both La Porte and Berrien
counties. Moderate to strong rip and structural currents are
expected.

An upper level ridge will amplify across the central and eastern
CONUS early next week. Surface high pressure builds over the eastern
US on Tuesday, with return flow and moisture from the Gulf ushering
in warmer than normal temperatures and humid conditions underneath
the peak of the upper level ridge over the Great Lakes. Our far
southwest will be the warmest with temperatures in the upper 80s for
highs Tuesday and peak heat indices around 95. Another frontal
system likely approaches by midweek with zonal flow aloft as the
ridge breaks down. Have maintained likely PoPs of 40-70% Tuesday
evening through Wednesday. There are still some uncertainties with
this system in regards to exact timing and placement of the cold
front. This system may be slow moving or potentially even stall to
our northwest (still mixed model guidance results on how fast it
actually comes through our area or not). Rain/storm chances midweek
will be highly dependent on where the periphery of the ridge ends up
(which model guidance has routinely struggled with in recent
months). With forcing expected to be weak as of now, severe weather
is not expected at this time, but we will have to monitor trends in
the coming days.

Our forecast area looks to remain sandwiched between hot and humid
air to our south and cooler, drier air to our north for the
foreseeable future, with a trend towards drier than normal
conditions by late September.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 115 PM EDT Sat Sep 12 2026

Shortwave responsible for showers and MVFR ceilings at KFWA will
push eastward over the next 2-3 hours, bringing a return to VFR
conditions that will persist through the evening. No thunderstorms
are expected. Some patchy fog then possible early Sun morning
at KFWA given light winds and residual moisture but confidence
in widespread/dense fog remains low. VFR expected to persist
through the period at KSBN given drier conditions there.

&&

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

&&

$$

DISCUSSION...Johnson
AVIATION...AGD