659
FXUS63 KIWX 151927
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
327 PM EDT Tue Jul 15 2025

.KEY MESSAGES...

- Hot and humid conditions expected through Wednesday. Heat
  indices in the lower to middle 90s for Wednesday.

- Low chances of showers and thunderstorms later this afternoon
  south of US 24, with increasing chances of showers and a few
  storms later tonight into Wednesday AM, mainly along and east
  of I-69.

- Another round of thunderstorms Wednesday night into early
  Thursday morning. There is a Marginal Risk of severe storms
  mainly Wednesday night for wind.

- Brief period of less humid conditions for Thursday and Friday
  before heat and humidity returns beginning Saturday.


&&

.DISCUSSION...
Issued at 251 PM EDT Tue Jul 15 2025

Warm frontal boundary draped west to east over the southern
portions of the CWA this evening will increase chances for
showers/thunderstorms especially south of US-24 before the
boundary moves northward and increases chances for
showers/thunderstorms once again with best chances east of
I-69. This boundary will allow for more humid airmass to stream
northward bringing higher heat indices to the area for
Wednesday.

A cool frontal boundary to the west of the area over WI/IL will
push eastward tomorrow evening and thunderstorm activity is
expected along and just ahead of the frontal boundary. This has
the potential to bring chances of strong to possibly severe into
the CWA on Wednesday night into early Thursday morning. SPC
currently has our area for a Marginal Severe Risk. The main question
will be the timing. As in recent disturbances the activity over
IL had diurnally weakened significantly by the time it entered
our CWA. This is the expectation for this disturbance. However,
a few isolated strong to severe outflow gusts may be possible
with any of the surviving storms due to the slightly stronger
shear along the boundary.

A drier and cooler airmass will push into the area in the wake
of the cool front on Thursday and Friday. This will be a nice
change in pace albeit a short one so enjoy it. There still is
some chances for some diurnally driven instability
showers/thunderstorms. However, these thunderstorms would be
more of the garden variety with the lack of shear and lifting
mechanism.

Saturday a more zonal flow develops across the area and
continues into the beginning of next week with periods of weak
diurnally driven encroachment of moisture from the south each
day. High temperatures will get into the low to mid 80s each
day and dew points into the lower 70s. By Tuesday, ridging
starts to push northward and will bring increasing temperatures
and slightly more humid conditions into the area. Highs in the
upper 80s on Tuesday and into the low 90s by next Wednesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 143 PM EDT Tue Jul 15 2025

A frontal boundary situated well northwest of the lower Great
Lakes places the terminal sites in south southeast flow with
increasing moisture as precip water values rise through this
aftn into tonight. Isolated storms have already developed
across the southern half of Indiana this aftn. moving
northward. With loss of day time heating, this activity is
expected to diminish. Will introduce chc pops toward the end of
the fcst period as upper level dynamics become more favorable
for precip occurrence at the terminal sites.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert until 4 AM CDT Thursday for INZ103-203.
OH...None.
MI...Air Quality Alert until 5 AM EDT Thursday for MIZ078-177-277.
MARINE...None.

&&

$$

DISCUSSION...Andersen
AVIATION...Frazier