Severe Thunderstorm Warning 119, NWS Northern Indiana

Area Forecast Discussion
National Weather Service Northern Indiana
236 PM EDT Sat Jul 26 2025

.KEY MESSAGES...

- Shower and thunderstorm chances continue this evening with
  heavy rain leading flooding and gusty to damaging winds being
  the main threat.

- Thunderstorm chances continue Sunday, but begin to wane as
  heat begins to build into the work week. Better chance for
  heat indices reaching 100+ degrees exist for Monday and
  Tuesday. Perhaps Sunday as well.

- A cold front will bring more storms on Wednesday with cooler
  and less humid conditions to end the week.

&&

.DISCUSSION...
Issued at 218 PM EDT Sat Jul 26 2025

Still under an airmass with 70+ dew points, 16C 850 mb dew points
and 2 to 2.5 inch PWATs as various shortwaves/MCVs move through in
the flow. The shortwaves' tracks took them through our northern
areas this morning (even though storms stayed along and south of US-
30), but an adjustment will take place as a low level jet shifts
southward and more through the center of the area. This allows
storms to move through this evening with around 30 kts of effective
shear and pockets of 100 m2/s2 of effective helicity and some
instability work with. Inverted-v like soundings are notable in HRRR
output, but may become more possible when heating occurs as clouds
break. Instability could be more elevated otherwise. All this in
mind, flooding and damaging wind appear to be the main threats, but
a quick spin up is not out of the question with the low LCLs. This
area of better shear is out of the area by 6z tonight, but the
better instability wanes closer to sunset. Sunday, the line of
forcing collocated with the front shifts so that it bisects the
area. However, weaker forcing and a departing low level jet likely
keeps coverage and intensity of showers, and perhaps a storm with
instability still around, lower than what we've had. Low level
moisture may be stubborn to evaporate tomorrow morning, which may
make it more difficult get better heating started and provide more
confidence behind a heat advisory. As a result, have decided to
allow the next shift to have one last look at a potential heat
advisory for Sunday.

After Sunday afternoon's height rises, more steady heights indicate
some possibility for showers and storms. Lid strength appears to be
conducive even by mid-morning so showers may start as early as then
or into midday, also throwing shade at confidence for heat headlines
on Monday. Even the normally wet-biased NAM keeps showers isolated
until the evening, though. High temps currently forecast for the 90s
and dew points in the 70s point towards surpassing 100 degree heat
indices with 105 heat indices in play as well. And this is the same
set up for Tuesday with 90s for highs and 70s for dew points, but
this time, there is no nearby trough.

By the time we get to Wednesday, a cold front begins to push
southward towards the area. Highs in the 80s are forecast along with
dew points in the 70s as thunderstorms may cut into how high temps
can get. But storm timing will need to be taken into account. There
is the potential that Wednesday ends up warmer if storms hold off.

For Thursday, an upper low over eastern Canada shifts southward and
CAA arrives on the heels of the FROPA, which occurs Wednesday night
into Thursday morning. Highs in the 70s and dew points in the 50s
represent a cooler and drier end of the work week. Dry weather
probably remains through the weekend as a sprawling 1025 mb
high takes its time to saunter through this neck of the woods.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 223 PM EDT Sat Jul 26 2025

Chances for showers and thunderstorms are the main group
producers for this TAF issuance. Will have tempo groups handle
MVFR chances until around sunset at SBN. Shower and storm
chances may continue overnight and we'll have to watch for a
chance for flight condition reductions around 9z into Sunday
morning at SBN, but didn't have enough confidence to add with
this issuance. Wind continue to prevail out of the southwest
until we get to Sunday morning when more westerly and
northwesterly trajectories take over.

&&

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

&&

DISCUSSION...Roller
AVIATION...Marsili/Roller

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