textproduct: Indianapolis

KEY MESSAGES

- Hot and humid condition expected for much of this week with multiple days in the 90s and heat indices over 100 degrees

- Heat Advisory in effect this afternoon through Thursday

- Thunderstorm chances will increase late week into the holiday weekend

DISCUSSION (This evening through Monday)

Issued at 257 PM EDT Mon Jun 29 2026

Ensemble guidance is in excellent agreement showing anomalous ridging this week across the Ohio River Valley. Ensemble mean 500mb heights around 598dm are roughly 2-3 sigma above average for this time of the year. Ridging remains roughly in place through about Thursday, before gradually drifting eastward and weakening somewhat. At the surface, prolonged southerly flow will continue to allow moisture and warm air to flow northward.

The warm and deeply subsident atmosphere should act to prevent shower or thunderstorm activity. Compressional heating combined with modest warm air advection is expected to result in above-normal warmth this week and likely into this weekend. High temperatures in the low to middle 90s are probable, with lows in the 70s. Additionally, dew points in the 70s will contribute to high heat indices between 100-110 all of this week. A Heat Advisory has been issued through Thursday evening.

As the ridge gradually drifts eastward later this week, subsidence weakens allowing for the possibility of daytime / pop-up showers and thunderstorms beginning on Friday. Severe weather is not currently expected, since the jet stream is far to our north, but isolated downbursts can never be ruled out in low-shear situations. Guidance shows a weak cold front potentially arriving early next week, with an increased risk of showers/storms. Upper-level flow remains minimal, however, and organized severe weather does not appear likely at this time.

AVIATION (00Z TAF Issuance)

Issued at 703 PM EDT Mon Jun 29 2026

Impacts:

- Patchy ground fog possible early Tuesday morning

- Wind gusts into the upper teens possible at one or more sites Tuesday afternoon

Discussion:

VFR conditions are likely to prevail throughout the period.

Given the very moist airmass in place, brief visibility restrictions near daybreak cannot be ruled out, particularly at the outlying sites, but this is too low probability for mention, and if it did occur, would likely be short and transient.

Winds will generally remain south to southwesterly throughout the period, with sustained winds overnight at 5-10KT or less, and during the day 9-12KT with a few gusts to around 18KT possible, primarily at LAF which will be furthest from the surface high, though an occasional gust at the other sites cannot be entirely ruled out.

IND WATCHES/WARNINGS/ADVISORIES

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