150
FXUS63 KIWX 241010
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
610 AM EDT Tue Jun 24 2025

.KEY MESSAGES...

- An Extreme Heat Warning continues in effect through through
  this evening for widespread heat indices around 100 to
  locally 105 degrees.

- Cumulative effects of long-duration heat will likely cause
  significant impacts at least through Friday, especially with
  vulnerable populations.

- Mild overnight lows in the 70s will exacerbate the heat wave.

- Thunderstorms will become numerous most afternoons and
  evenings through Friday. Storms may become marginally severe
  today and Wednesday with damaging winds will be the main hazard.

&&

.DISCUSSION...
Issued at 218 AM EDT Tue Jun 24 2025

The Heat Wave will persist today for the fourth day with afternoon
highs in the low to mid 90s and heat indices around 100 to locally
105 degrees. Therefore, have kept the Excessive Heat Warning in
effect today. Research has shown these hot conditions are especially
brutal on the more vulnerable populations where the heat has
significant impacts with multiple hot days in a row. Highs are
forecast to be in the upper 80s to around 90 through Sunday which,
if all of these hot days are considered, would bring the heat
wave to 8 days (June 21-28).

In addition to the heat, thunderstorms will enter the forecast
today. The storms will be most numerous during afternoon and
evenings through Friday. Intense heating today and Wednesday may
bring some storms to the threshold of becoming severe. Although
wind flow and wind shear will be generally weak, afternoon
instability may top 3000 J/Kg per NAM BUFKIT CAPE favoring a
high correlation with a diurnal window of 19Z to 01Z. There is
a signal for heavy precipitation given the likely slow storm
movement and anomalously high precipitable water values near 1.8
inches which is above the 95th percentile for the forecast area
for this time of year.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 605 AM EDT Tue Jun 24 2025

Existing TAFs were on track resulting in little to no change for
this issuance. An outflow boundary is located SW to NE across
northern IN this morning. This will likely serve as a point of
thunderstorm initiation later this afternoon. High resolution
guidance favors storms to develop near KSBN but timing varies
somewhat. There appears to be a small concensus of models that
suggest TSRA stays north of KFWA thanks to our dominant ridge.
I`ll maintain the PROB30 for the time being. Low confidence on
whether or not additional storms overnight arriving from
Illinois impact KSBN. This second round would be highly
dependent on the afternoon`s storm coverage.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Extreme Heat Warning until 8 PM EDT /7 PM CDT/ this evening
     for INZ005>009-012>015-017-018-020-022>027-032>034-103-
     104-116-203-204-216.
OH...Extreme Heat Warning until 8 PM EDT this evening for OHZ001-
     002-004-005-015-016-024-025.
MI...Extreme Heat Warning until 8 PM EDT this evening for
     MIZ078>081-177-277.
MARINE...None.

&&

$$

DISCUSSION...Skipper
AVIATION...Brown