416 FXUS63 KIWX 291719 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 119 PM EDT Mon Jun 29 2026 .KEY MESSAGES... - Extreme Heat Warning is in effect through Thursday evening for an extended period of high heat indices and limited nighttime cooling. - Heat may remain a concern Friday, but chances for showers and thunderstorms begin to increase resulting in lower confidence on the amount of impacts. && .UPDATE... Issued at 955 AM EDT Mon Jun 29 2026 Sfc warm front (essentially shift of winds to SW and a pronounced increase in dewpoints) was located from GRR SE to near Lima, OH. The showers that were ahead of this earlier have dissipated. The front will clear the area over the next couple of hours with 10 am ET temps already in the lower 80s southwest of the front. 2 areas of minor interest are 1) patch of low clouds moving east into our western counties and 2) southward moving feature (gravity wave or elevated outflow) from the convection across northern MI. 12Z RAOBs showing a very strong cap in place behind the warm front with ILX showing +15 C at 700 mb, DTX +11 and ILN +13. Typically anything above 12 C is sufficient to limit updrafts in cu. With regards to temps and the above noted features, there could be some brief slowdowns in the rising of temperatures. However, the strong June sun will quickly catch up in their wake so forecasted highs and heat indicies remain on track. && .DISCUSSION... Issued at 208 AM EDT Mon Jun 29 2026 An isolated area of showers persists early this morning associated with upstream convection earlier in the day, embedded within an upper-level disturbance now spilling over the eastern Great Lakes. Despite an overall absence of meaningful upper-level support, this activity has survived within a narrow corridor of 500 j/kg of MUCAPE and mid-level lapse rates near 7.5 C/km. An Extreme Heat Warning remains in effect through Thursday as a 594 dm ridge builds over the area. Daily highs in the 90s with afternoon heat indicies of 100-105 can take its toll. As mentioned in this space, heat headlines may need to carry on into Friday but the possibility of showers and storms diminishes confidence somewhat. During this stretch of heat, the NAEFS depicts 99th percentile temperatures and upper-level heights relative to 1979-2009 climatology. This highlights the magnitude of this bout of heat. Precipitable water values are in the 90th percentile, marking an unseasonably humid air mass. High temperatures are likely safe this week, with records of 98 to 101 noted at Fort Wayne and South Bend. However, "warm" low temperature records may be set, with records currently in the mid- 70s. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 112 PM EDT Mon Jun 29 2026 VFR conditions expected through this TAF period. Some haze/mist certainly would be possible over the next several days but at this time confidence is low and have left any mention in the overnight hours even with the small dewpoint depressions. Also, a few to scattered flat cumulus may be possible with the daytime heating/surface instability but likely around 5000 ft and again not high confidence at this time. Southwesterly winds will become breezy by Tuesday afternoon with the diurnal heating and gusts up to 20 kts expected. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Extreme Heat Warning until 8 PM EDT /7 PM CDT/ Thursday 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 Thursday for OHZ001-002- 004-005-015-016-024-025. MI...Extreme Heat Warning until 8 PM EDT Thursday for MIZ078>081- 177-277. MARINE...None. && $$ UPDATE...Fisher DISCUSSION...Brown AVIATION...Andersen