633
FXUS63 KIWX 142338
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
738 PM EDT Mon Sep 14 2026

.KEY MESSAGES...

- Turning hot and humid Tuesday and Wednesday. Shower and
  thunderstorm chances return Tuesday afternoon through
  Wednesday (40 to 70%). Chances may linger into Thursday as
  well.

- There is a marginal risk for isolated strong to severe storms
  Tuesday mainly between 6 pm and midnight. Main threat is
  damaging winds if storms become severe. Confidence remains
  low at this time.

- There is a moderate swim risk for Lake Michigan beaches along
  the Berrien Co, MI shoreline Tuesday. Breaking waves and
  currents expected.

&&

.DISCUSSION...
Issued at 147 PM EDT Mon Sep 14 2026

Very pleasant temperatures in the 70s and dewpoints in the 40s will
shift away as the sfc ridge moves east and an increasing low level
flow starts ushering much higher dewpoints to the area. This will
take a bit of time, with values into the low to mid 50s by 12Z Tue.
Off to our NW, an axis of much higher dewpoints will be pooled along
a slow moving frontal boundary that is expected to approach later
tomorrow and linger across the region (in a weaker state) through
Thursday. Dewpoints and low level temps will climb through the day
with a much more muggy feel returning by afternoon. High temps
before any convection occurs will reach well into the 80s for most
locations and if cloud cover stay away long enough, a few 90s are
possible in SW areas.

Models have generally backed off on upstream convection making it
into NW parts of the area as it encounters the drier air mass and
outruns the better forcing. As we move into Tuesday afternoon and
beyond, this changes with at least chance pops warranted as leftover
outflow boundaries that may drift in during peak heating interact
with increasing CAPE. There seems to be a continued lean towards
better development in the 20 to 22Z time frame, mainly NW but
honestly could end up just about anywhere. These then progress
southeast through about 2Z to 3Z Wed before shifting out of the area
or weakening. Shear profiles are on the lower side (25 to maybe 35
kts) for some organization of convection, and decent low level lapse
rates will help with the initial lift, but mid level lapse rates are
quite unfavorable for more robust convection. SPC has maintained the
Marginal Risk for severe storms with some gusty wind potential for
those storms that can interact with boundaries and maybe sustain
some briefly better updrafts and cores.

Beyond 6Z Wed forecast becomes even more challenging as frontal
boundary slowly weakens and stalls over the general area with models
struggling (as to be expected) with the handling of subtle waves and
possible new development or propagation of upstream convection.
Given the amount of lingering moisture in the area and at least some
instability, it won`t take much to pop additional showers and
storms, thus warranting the chc to likely pops through Thursday. By
no means does it look like a washout with periods of little/no
precip likely in between waves, but no way to time those out at this
point in the forecast. Severe threat should be very minimal, if non
existent, but heavy rain/localized flooding could become an issue
with high PWATs and any repeated training of multiple rounds of
convection. Marginal risk for Excessive Rainfall remains in place
Tue and Wed and is reasonable.

No changes beyond Thursday as models seem to want to push the
ridging north into MI for the weekend. However, history over the
past several weeks in this setup has pointed towards low confidence
on how much of this comes to fruition. As a result, blend is left
alone with some slgt chc to chc pops, especially Sat.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 735 PM EDT Mon Sep 14 2026

As surface high pressure escapes eastward, low pressure passes by to
our north in Canada. This evolution allows a warm front to push
through Tuesday morning allowing moisture to push in. Depending on
cold front and convergent boundaries, shower and storm chances
increase. The first instance of such an episode is Tuesday morning
around 12z for SBN. RAP time-sections indicate there`s quite a bit
of dry air that needs to be overcome below 700 mb so there`s still
some uncertainty on start time. Chances continue in the vicinity
of SBN through the morning. FWA takes even longer to moisten up,
but there`ll be thunderstorm chances that erupt in the late
afternoon time frame as long as its largely unimpeded by cloud
debris. Given dry air extent, it looks like we may be harder
to get MVFR conditions into SBN in the morning, but chances
are, during the afternoon MVFR conditions will be more likely
with IFR more possible by 00z time frame. FWA likely sees a
quicker ramp of adverse flight conditions closer to the 00z
time frame with the initiation of storm chances.

We`ll also have some marginal LLWS between 10 and 16z at SBN.
Initial southeast winds slowly veer more southwesterly by Tuesday
afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 11 AM EDT Tuesday for LMZ043-046.

&&

$$

DISCUSSION...Fisher
AVIATION...Roller