Severe Thunderstorm Warning 281, NWS Northern Indiana

Area Forecast Discussion
National Weather Service Northern Indiana
640 AM EDT Wed Aug 12 2026

.KEY MESSAGES...

- Several more rounds of storms are expected today through late
  Thursday.

- Some of these storms may be severe with damaging winds and
  heavy rain possible. The best chances today are generally
  south of US-30.

- A flood watch remains in effect for areas along and south of
  US-30 today.

&&

.DISCUSSION...
Issued at 212 AM EDT Wed Aug 12 2026

Another challenging and very low confidence convection forecast for
today. Latest surface obs and mesoanalysis show frontal boundary
draped right along our southern CWA border. North of this front some
patchy fog has developed but visibilities are highly variable and
guidance suggests that will continue through the morning as cloud
cover increases so no plans for a dense fog advisory at this time.
This front will slowly lift NE through the early morning as the
nocturnal LLJ ramps up. Already seeing some convection fire along
this front but luckily it remains elevated with virtually no surface-
based instability in our area. Will still have to keep an eye on
this activity through the early morning though with some low-end
potential for hail and heavy rain in a region already water-logged.
Hi-res CAM's are struggling immensely to capture this activity and
subsequently predict evolution through the early morning. Forecast
confidence is low but based on overall mesoscale setup expect this
activity to continue and slowly expand NE through the early morning
as the LLJ intensifies and pushes very high theta-e air back into
our CWA (850mb dewpoints in excess of 16C).

There could be a brief lull during the late morning but attention
this turns to the potential for another MCS associated with
convection currently over SD. Here again confidence is not high but
hi-res guidance shows a little better agreement in an MCS tracking
through at least our southern half around midday. Unfortunately all
of the ingredients will be similar to yesterday (very high
instability and deep-layer shear) and a damaging squall line is a
possibility. Slight southward displacement of frontal boundary may
support a focus more toward central IN as reflected in the latest
SWODY1. However, it should be noted that several hi-res members
track this MCS further north with a track, timing, and intensity
eerily similar to yesterday. Straight-line winds would again be the
main concern but hail and an embedded tornado can't be ruled out.

The other issue will be heavy rain. Placement of the front and
convection predicted by several guidance members unfortunately
suggest the same area hit hard with heavy rain yesterday could be in
line to get another round of heavy rain today. Earlier noted
convective uncertainties remain but felt confidence enough to extend
the flood watch for our southern zones that received significant
rain yesterday. Ran the flood watch until 03Z to match up with
neighbors but if the midday convection plays out as expected it
could be canceled early.

With plethora of near-term challenges and uncertainties, did not
spend a lot of time on the later periods. Unfortunately, this front
hangs around through at least Fri morning with potential for several
more rounds of convection. The front finally does briefly surge
north late Fri into Sat which would bring some temporary relief
before the associated cold front arrives Sunday. Behind this front,
a more lasting period of dry weather is anticipated for early next
week.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 640 AM EDT Wed Aug 12 2026

Nocturnal LLJ and associated theta-e advection lighting up
numerous showers and storms around KFWA this morning. This
activity should wane shortly after 12Z but may persist slightly
longer. Ceiling forecast remains low confidence given highly
variable obs and guidance across the area but low-end MVFR is
still likely for a time this morning. Increasing confidence in
MCS passage around 18Z with return to VFR/tranquil conditions by
late afternoon.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch through this evening for INZ012>015-017-018-020-
     022>027-032>034-116-203-216.
OH...Flood Watch through this evening for OHZ024-025.
MI...None.
MARINE...None.

&&

DISCUSSION...AGD
AVIATION...AGD

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