textproduct: Indianapolis

KEY MESSAGES

- Hot and humid condition expected with highs in the 90s and heat indices peaking at 105 to 110 degrees in the afternoons through Thursday

- **Extreme Heat Warning** in effect through Thursday evening

- Thunderstorm chances will increase Friday through the holiday weekend

FORECAST UPDATE

Issued at 1000 PM EDT Tue Jun 30 2026

Conditions evolving as expected as June ends on a hot and humid note, with readings falling off a bit faster than expected amid mid-70s dewpoints. Diminishing low cumulus / high cirrus have been replaced by mainly clear skies that should be maintained through much of Wednesday. This will however increase chances of visibility reductions in overnight fog...especially south of the I-70 corridor where recent rainfall was heaviest. Minimum temperatures by early Wednesday will reflect dewpoint values...with 72-74 at most locations.

DISCUSSION (This evening through Tuesday)

Issued at 316 PM EDT Tue Jun 30 2026

Ridging and high pressure will persist for much of the week, keeping hot and humid conditions firmly in place. The ridge will finally start to break day and push east Friday and allowing for daily chances of showers and storms for the holiday weekend and into next week.

The primary focus will be on the heat and humidity with several more days of highs in the 90s and heat indices from around 100 to 110 each day. The hot, moist air is is being streamed into the region from the SW and Gulf which is helping to keep the dew points in the 70s. Increased subsidence over the Ohio Valley will limit clouds and diurnal cumulus clouds as well, especially Wednesday. Likely to see a slight increase in cumulus development Thursday as moisture pivots around the back side of the ridge and into the area, but it is shallow and should not have much impact on expected highs.

Long range guidance depicts upper ridging flattening out towards the end of the week with northwest flow developing aloft late weekend into early next week. A few shortwaves aloft are expected to track towards the region once the ridge begins to flatten. Weakening large scale subsidence and modest dynamics from the approaching impulses will provide greater opportunities for convection into the weekend. Diurnal convection can also be expected with strong daytime heating atop an anomalously moist PBL.

A few strong storms are possible with the potential for isolated intense downbursts in the moisture rich unstable environment during the afternoon or evening hours. Slow moving storms can also be expected as forecast soundings depict very weak flow throughout the column. This will support the potential for brief locally heavy rainfall and mostly prevent severe weather potential outside of the threat for isolated downbursts. A few MCSs may still develop upstream and propagate towards the region over the weekend, but specific details regarding this remain uncertain due to diverging model solutions.

Humid conditions will continue through the weekend while temperatures remain hot. Some slight relief from the heat appears increasingly likely into early next week as guidance suggest a front associated with a more organized shortwave could dive south. ECMWF and GEFS members differ on exact timing of the front though.

AVIATION (00Z TAF Issuance)

Issued at 717 PM EDT Tue Jun 30 2026

Impacts:

- SSW winds 7-12KT early this evening..and again Wednesday afternoon - Low chances of MVFR visibility in fog late tonight

Discussion:

Mainly VFR conditions are expected to prevail through Wednesday evening near central Indiana terminals. Generally FEW lower cumulus will dissipate through the early evening. Visibility reduction to MVFR in fog is possible through pre-dawn hours, but chances are too low to include in any TAF. Otherwise very humid heat wave to continue across the Midwest as Indiana sits under the northwestern quadrant of the subtropical upper ridge centered near Tennessee.

Scattered cirrus will overall decrease in coverage through early Wednesday...with mainly clear skies expected through the latter half of the TAF period. Winds within 190-240 degrees through Wednesday, will follow a typical diurnal variation...with sustained winds at 8- 12KT early this evening, falling below 7KT at most terminals by 04Z, and increasing within 5-11KT by Wednesday afternoon...although KIND will see 7KT or greater through most of the period.

IND WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM EDT Thursday for INZ021-028>031- 035>049-051>057-060>065-067>072.