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

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 (18Z TAF Issuance)

Issued at 157 PM EDT Tue Jun 30 2026

Impacts:

- Low Cu field through sunset

Discussion:

VFR conditions are expected to prevail throughout the period.

A low Cu field is expected through much of the rest of the daylight hours today sitting around 025 to 030 with thin cirrus clouds aloft at times. Mostly clear skies should then move in tonight and should last into tomorrow under ridging. Winds will generally be out the SW throughout the period with wind speeds of 5 to 10 kt. A few sporadic gusts, less than 20 kts are possible this afternoon.

Can't rule out patchy fog during the early morning hours given how humid conditions are across the area, but winds should be just high enough to prevent anything widespread or dense. Will continue to monitor and update if needed.

IND WATCHES/WARNINGS/ADVISORIES

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