Severe Thunderstorm Warning 239, NWS Northern Indiana

Area Forecast Discussion
National Weather Service Northern Indiana
331 PM EDT Mon Aug 10 2026

.KEY MESSAGES...

- Several rounds of strong to severe thunderstorms are possible
  into Tuesday. Damaging winds and large hail are the main
  concerns, but an isolated tornado or 2 is possible.

- Flooding concerns may increase depending on rainfall amounts
  across the area with each round of storms.

- Seasonable temperatures are expected to persist.

&&

.DISCUSSION...
Issued at 243 PM EDT Mon Aug 10 2026

Difficult forecast continues in regards to convection coverage
and timing over the next couple of days. Will focus on the next
24 hours or so as guidance seems to be flummoxed with this ring
of fire pattern that is currently sitting over our forecast
area. A stationary boundary continues to sit form west to east
over central IA, northern IL, and into northern IN/southern MI.
Convection has been firing along this boundary over the last day
or so and looks to continue to do so. With pretty much a lack
of any agreement in the different CAMs models uncertainty
remains pretty high on the exact timing and coverage of any
developing convection. Currently a couple of thunderstorms have
continued to form over northern IL and a couple of cells have
also popped up just to the southeast of our CWA. Watching for
possible backbuilding northwest from the cells to our southeast
and also further storm development eastward from the storms
over northern IL. A very moist airmass is in place with surface
dew points in the mid to upper 70s, PWATs also remain elevated
around 1.75". Instability is also abundant with SBCAPE values of
5000 to 6000 J/kg present this afternoon into the evening.
Effective bulk shear values around 40 kts will also be
available. The stationary boundary will most likely be the focal
point for initial storm development but with the amount of
instability present and this is what makes this forecast so
difficult is that any outflow boundary or weak disturbance is
enough to initiate further storm development out away from the
boundary. Pinning down where storms will and when will
ultimately develop continues to be the main quandry. However,
any thunderstorms that develop will have all threats available
especially wind, hail, and heavy rainfall but with SR Helicity
values around 100 m2/s2 and the close proximity of the boundary
will also allow for tornado spin ups. SPC still has our area
under a slight risk for severe weather tonight.

Overnight tonight there will continue to be periods of
thunderstorms pushing through the area in a more scattered
nature but a few lingering stronger cells that develop this
evening may continue to impact the area into the overnight
period and even continue into the morning period on Tuesday.
Some indications do having a brisk southward push of the
boundary by Tuesday afternoon and this will increase the forcing
available and would help to move the activity into central
Indiana, but again with models struggling in the near term
really do not have high confidence on any solution. SPC
currently has the southwest half of our CWA in an enhanced risk
of severe storms tomorrow. This does make sense with the better
forcing and some models hint at a linear convective band pushing
from the northwest parts of the CWA southward into the southern
half of the CWA. Again, all threats look to be possible but the
main threats will be damaging winds and heavy rainfall on
Tuesday.

With the southward shift to the boundary the SPC is calling for
a marginal severe risk for our southwestern portions of the CWA
on Wednesday. With the still quasi zonal flow remaining in place
on the northern side of ridging over the southeast CONUS
temperatures look to remain seasonable through the weekend.
Still taking the longer term with a grain of salt as the near
term evolution will lead to the longer term outcome.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1228 PM EDT Mon Aug 10 2026

MVFR stratocu in the vicinity of a frontal boundary should mix
into low VFR with some additional heating this afternoon. Main
focus otherwise is on the convective potential late this
afternoon into tonight. Latest observational and model data
suggest the late afternoon and evening for the best opportunity
for scattered convection as a weak impulse approaches from the
west amid ample MUCAPE. Brief IFR/LIFR conditions and gusty
winds possible if storms impact the terminals.

&&

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

&&

DISCUSSION...Andersen
AVIATION...Steinwedel