textproduct: Indianapolis

KEY MESSAGES

- Peak afternoon heat index values between 105 to 110 through Friday

- Extreme Heat Warning in effect through 8 PM Friday

- Thunderstorm chances will increase Friday through the holiday weekend

- Isolated damaging wind gusts and localized flooding are the primary threats with thunderstorms

DISCUSSION (This evening through Thursday)

Issued at 222 PM EDT Thu Jul 2 2026

Overview.

An intense heat wave will continue across central Indiana through Friday with dangerously hot and humid conditions expected. The Extreme Heat Warning continues through 8pm Friday with peak heat index values of 105 to 110 possible each afternoon and little to no relief from the heat overnight. Look for some slight relief this holiday weekend into early next week as storm chances begin to increase.

Today through Friday night...

Upper ridging will continue to break down through the end of the week allowing for rain chances to eventually return late in the day Friday from an approaching shortwave. While the ridge should break down, the hot and humid airmass is already in place so look for dangerously hot conditions to continue through Friday with little relief overnight.

Look for large scale subsidence to keep weather conditions mostly quiet through much of the day Friday. Isolated diurnal convection can then be expected towards the late afternoon or evening hours as subsidence decreases. Greater coverage of storms appears possible towards NW counties due to stronger forcing from the approaching wave. Deep-layer wind shear for storm organization appears weak, but strong destabilization and steep low-level lapse rates could support isolated damaging wind gusts Friday afternoon or evening. Storm mode will likely be short lived pulse thunderstorms or loosely organized multicell clusters.

Saturday through early next week...

Guidance depicts a few shortwaves moving through aloft during the period. Weakening large scale subsidence and at least modest dynamics from the approaching impulses will provide greater opportunities for convection, particularly over the weekend. The greatest storm chances can be expected during the afternoon and evening hours with strong daytime heating atop an anomalously moist PBL.

Isolated strong to severe storms are possible given strong destabilization each afternoon. Forecast soundings also show very steep lapse rates with high DCAPE values. The primary threat would be isolated damaging wind gusts from microbursts in the weakly sheared environment, mainly during the afternoon or evening hours. A few models also still suggest the potential for a few MCSs to develop near the region over the weekend. Confidence on this scenario remains limited due to varying model solutions, but overall flow could allow for any storm cluster to propagate towards central Indiana supporting the potential for isolated damaging wind gusts. Weak deep-layer shear should tend to limit maintenance of any MCS or storm cluster.

Humid conditions will continue through the weekend while temperatures remain hot or very warm. Some slight relief from the heat can be expected this weekend into early next week with additional chances for convection. Guidance also depicts a front associated with a more organized shortwave pushing through the area early next week. ECMWF and GEFS members differ on exact timing and, but the boundary will likely reinforce low convective chances along with helping to trend temperatures closer to seasonal averages.

AVIATION (00Z TAF Issuance)

Issued at 738 PM EDT Thu Jul 2 2026

Impacts:

- Scattered thunderstorms possible late in the day on Friday and into Friday night

Discussion:

VFR conditions through tonight except for low probability patchy ground fog at typically fog-prone terminals.

VFR conditions continue into early Friday afternoon with cumulus development expected. By around 23z Friday convective development is anticipated with storms possible until the end of the TAF period (06z at IND). Storms look to be widely scattered, but could produce downbursts capable of briefly strong wind gusts. Included a Prob30 group at IND to account for this possibility.

Winds are expected to maintain a generally southwesterly component through the forecast period. Light and variable conditions are possible during the overnight hours.

IND WATCHES/WARNINGS/ADVISORIES

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