301
FXUS63 KIWX 130535
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
135 AM EDT Sun Jul 13 2025

.KEY MESSAGES...

- Showers and thunderstorms exiting by 9 PM EDT. Local wind
  gusts to 40 mph.

- Brief reprieve from high humidity with dry conditions Sunday
  and Monday, but heat is expected to return by Tuesday and
  Wednesday.

- Wildfire smoke returns aloft Sunday and Monday.

- Next best chances for rain/storms will be Wednesday and
  Thursday.

&&

.UPDATE...
Issued at 730 PM EDT Sat Jul 12 2025

Sub severe thunderstorms are persisting along the lessening
instability gradient across far SE portions of the area with the
last area moving through NW Ohio and likely to exit between 8
and 9 pm EDT. Wind gusts have been in the 30 to 40 mph range
with the storms thus far and with loss of heating, no
intensification is anticipated. Will do some minor grid cleanup,
but overall forecast remains on track.

&&

.DISCUSSION...
Issued at 234 PM EDT Sat Jul 12 2025

An MCV coming out of southern Illinois this afternoon aided by lift
from an approaching cold front will allow for scattered
thunderstorm development this afternoon and evening. The cold
front is currently draped from Rockford, IL southeast to St
Louis, MO, however, a subtle wind shift is already preceding
the front. Gravity waves leftover from last night`s MCS in
Illinois have cleared the area and clearing is evident on
visible satellite imagery. The forecast area should continue to
destabilize with highs in the upper 80s to near 90 and dewpoints
recovering in the low 70s. Heat indices are still expected to
peak this afternoon between 95 and 100 degrees, especially
across northwest Ohio. Destabilization should occur between 3-5
PM and clusters/a broken line of storms should form across
central and northern Indiana. SPC has maintained their Slight
Risk for northeast Indiana and northwest Ohio. The best window
for severe weather should be along and east of I-69 from 4-9 PM
EDT. There is only 20-25 kts of shear today and it is offset
from a decent CAPE gradient with 2000-2500 J/kg SB CAPE across
far northeast Indiana and into northwest Ohio. While the overall
setup is unimpressive, steeping low level lapse rates coupled
with ~1000 J/kg of DCAPE suggest that isolated damaging winds
gusts could be possible this afternoon and evening if storms can
maintain their updrafts. Even if storms are sub-severe, 40-50
mph gusts could still take down tree limbs and powerlines.

Tonight, the cold front will slowly move through the area. Storms
will taper off after sunset with the loss of diurnal heating. By
sunrise on Sunday, the cold front should be mostly through the area.
A few storms could redevelop south of the US 24 corridor in the
afternoon and evening, but chances are very low (20% or less).
Northwest flow behind the front will usher in a brief reprieve
from the heat and humidity on during the afternoon on Sunday.
Highs will be in the mid 80s with dewpoints only in the low 60s!
Smoke from Canadian wildfires will also get dragged in across
the Upper Great Lakes behind the cold front. An Air Quality
Alert has been issued for southwest Lower Michigan from midnight
EDT tonight through Noon EDT on Monday. Latest HRRR and RAP
model runs depict that the smoke largely remains aloft over
Lower Michigan and far northern Indiana, although increasing
northwest winds may mix some of it down to the surface during
the afternoon on Sunday.

The relief from the heat and high humidity is, unfortunately, short
lived. An upper level ridge and surface high pressure build across
the Great Lakes region into early next week, bringing mainly dry
conditions through midweek. Heat and humidity return with highs in
the upper 80s Tuesday and Wednesday. The next best chances for
rain/storms arrives Wednesday afternoon/evening and into Thursday as
a low pressure system moves through the Midwest and Upper Great
Lakes.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 124 AM EDT Sun Jul 13 2025

The edge of a large upper level ridge will encroach into
northern Indiana. Given weak subsidence and extremely stable mid
level lapse rates near 5C/Km, have kept showers and storms out
of TAFs. Otherwise, winds will be light and conditions VFR.
Scattered cumulus is possible by late afternoon, but should not
be operationally significant.


&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...Air Quality Alert until noon EDT Monday for MIZ078>081-177-277.
MARINE...None.

&&

$$

UPDATE...Fisher
DISCUSSION...Johnson
AVIATION...Skipper