724
FXUS63 KIWX 120514
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
114 AM EDT Sat Jul 12 2025

.KEY MESSAGES...

- A few showers and storms early Saturday morning are possible
  across NW Indiana and SW Lower Michigan.

- Better chances for rain/storms between 2-10 PM EDT Saturday,
  especially along and east of I-69. Storms may be strong to
  severe with lightning, heavy rainfall, and gusty to damaging
  winds.

- Hot and humid conditions for the weekend, with highest heat
  indices expected in the mid to upper 90s for Saturday
  afternoon.

- Brief shot of dry and less humid weather Monday, but heat is
  expected to return by Tuesday and Wednesday.

&&

.UPDATE...
Issued at 749 PM EDT Fri Jul 11 2025

Line of convection steadily moving eastward across northern IL
at this time. The expectation is we should see these storms
weaken through time as they move eastward into our CWA much like
yesterday evening. A few of the showers/storms may survive into
the western and northwestern portions of the CWA tonight around
midnight CDT and 1AM EDT. Have adjusted pops and weather to
reflect this timing/possibility.

&&

.DISCUSSION...
Issued at 225 PM EDT Fri Jul 11 2025

A decaying round of showers and a few storms moved through the area
this morning as part of an overnight MCS that went through Iowa and
northern Illinois. In it`s wake, pockets of clearing have become
evident on visible satellite imagery. While widespread redevelopment
of showers and storms is not expected today, can`t rule out isolated
pop-up storms this afternoon and evening. CAMs still have quite a
high spread in outcomes over the next 12-24 hours, but it appears
like the highest chances for redevelopment along any remnant outflow
boundaries will be tonight across eastern Iowa, northern Illinois,
and southern Wisconsin with yet another MCS. Given southwesterly low
level flow tonight, it`s possible that this system to our west holds
together. If it does, NW Indiana and SW Lower Michigan could get in
on some rain/storms during the evening and overnight hours into
early Saturday. There will be some shear to work with given that
surface flow will be southerly this evening and mid level flow will
be southwest. Instability will be modest but ample moisture will
allow for heavy, efficient rain rates. Should storms develop,
strong wind gusts to 50 mph and heavy rain will be possible
across the northwest portion of the forecast area.

Hot and humid conditions prevail on Saturday with highs in the low
90s and dewpoints into the low to mid 70s. Peak heat indices in the
afternoon will likely be in the mid to upper 90s, although
rain/storms may bring some relief by late in the afternoon and
evening. Saturday`s chances for rain/storms are dependent on the
evolution of the overnight decaying MCS. Some of the CAMs,
particularly, the HRRR, depict quite a strong MCS developing to our
west tonight, which would likely leave an outflow boundary (or
multiple) in it`s wake. On Saturday, scattered clusters of storms
are likely to develop ahead of a cold front in the afternoon and
evening. The Storm Prediction Center has areas along and east
of I-69 in a Slight Risk (level 2 of 5) for severe weather on
Saturday. The best environment for severe storms will be east of
I-69, however, storms may develop along any remnant outflows
leftover from the aforementioned overnight MCS. Destabilization
may occur as early as 1-2 PM EDT, but best chances for storms
will likely be between 4-10 PM EDT Saturday. With minimal shear
once again (less than 20 kts), moderate instability (~2000-2500
J/kg MUCAPE) and steeping low level lapse rates, gusty to
damaging winds will be the primary threat. Given tall, skinny
CAPE profiles, low level southwest flow parallel to the cold
front, and PWATs around 1.5-2", heavy rain and flooding will
also be possible Saturday. WPC does have much of our forecast
area in a Marginal Risk (level 1 of 4) for isolated instances of
flash flooding on Saturday afternoon and evening.

By Sunday, the cold front will have mostly cleared the area. A few
storms could redevelop south of the US 24 corridor in the
afternoon and evening if the front hasn`t entirely cleared the
area by then. It will be a similar setup to Saturday with
limited shear and moderate instability. Northwest flow behind
the front will usher in a brief reprieve from the heat and
humidity late in the day Sunday into Monday.

An upper level ridge and surface high pressure build across the
Great Lakes region into early next week, bringing mainly dry
conditions until midweek. Low chances (around 20%) for diurnally
driven showers and storms exist Monday and Tuesday. Heat and
humidity return with highs in the upper 80s to low 90s Tuesday
and Wednesday. The next area-wide chance for rain/storms
arrives Wednesday afternoon/evening along a cold front.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 114 AM EDT Sat Jul 12 2025

Upstream convection over Chicago continues to slowly weaken with
little eastward progress as ridge holds firm over northern
Indiana. Hi-res models suggest a few showers may move into KSBN
around 12Z with some brief MVFR ceilings possible. Otherwise
attention turns to afternoon convection chances as front slowly
approaches and local area finally destabilizes. There is very
little forcing during peak heating though and hi-res CAM`s show
a wide variety of solutions with variable timing and coverage.
Best chances will be at KFWA but can`t rule out a storm at KSBN.
Given uncertainty in timing and coverage will hold with just a
PROB30 mention for now.

&&

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

&&

$$

UPDATE...Andersen
DISCUSSION...Johnson
AVIATION...AGD