textproduct: Indianapolis

KEY MESSAGES

- Heat Advisory in effect for all of central Indiana through Friday evening with peak heat index values up to 108 are possible each afternoon

- Isolated to scattered thunderstorms will be possible at times late this week through the weekend.

FORECAST UPDATE

Issued at 959 PM EDT Wed Sep 2 2026

Persistent unseasonably warm/hot pattern under broad stacked ridge over most of the CONUS' eastern two-thirds...will maintain another rain-free yet humid overnight with light southwest flow becoming variable by pre-dawn hours. Patchy fog will be possible towards dawn amid elevated dewpoints, but impactful visibility reductions are not expected. Temperatures generally in the low to mid-80s as 0f 930 PM EDT will slowly fall to 72-76 by early Thursday.

DISCUSSION (This evening through Wednesday)

Issued at 254 PM EDT Wed Sep 2 2026

Strong mid/upper-level ridging over the CONUS remains in place through the end of the week, amplifying over the Plains this weekend. With the main ridge axis amplifying to our west, troughing over the northeastern US may nudge southwestward into Indiana late Saturday or Sunday. This could allow for a backdoor cold front out of the northeast, bringing an end to the current heat wave. The reprieve may not last long as ensemble guidance hints at the ridge building back eastward next week with above-average temperatures returning to the region.

In the meantime, heat and humidity continue to build over the Ohio River Valley. Temperatures have risen into the mid 90s with dew points in the low 70s. ACARS soundings out of IND show around 1500 J/Kg MLCAPE with guidance showing an increase to around 2500 J/Kg later this afternoon. The IND soundings also show a fairly deep but modest cap around 700mb. The profile overall is rather dry as well. Nevertheless, CAM guidance hints at some isolated convective development later today into the early evening. Forcing seems nebulous at best, and initiation will likely depend on subtle features such as horizontal convective rolls. Severe potential appears low, but with such a dry profile amid relatively steep lapse rates, a downburst capable of strong winds cannot be ruled out. Overall, chances of any one location experiencing convection today is low and severe convection even lower.

Thursday is similar to today with heat, humidity, and afternoon/evening storm chances. Thunderstorm potential looks to be a bit better than today due to influence from upstream convection (remnant outflow). The greatest potential exists across our northern CWA, and especially into northern Indiana. Depending on how upstream convection evolves overnight which determines the position of the outflow boundary, subsequent development may not even reach central Indiana. Isolated convection is also possible further south but chances are low. Severe potential exists in the form of strong wind gusts due to steep low-level lapse rates and high DCAPE (over 1000 K/Kg). Like today, overall chances are still low and severe potential even lower.

By Friday, the amplifying ridge to our west will allow upper flow to become more northerly. Guidance shows northeasterly surface flow over Ohio pushing a thermal gradient southwestward towards Indiana. Upstream convection may tend to ride along this gradient within the northerly flow aloft. Low-level flow over Indiana is out of the west- southwest at the time, which may encourage some west/southwestward propagation. Like with any potential late summer MCS, strong winds and flooding are the primary hazards. Activity may linger into Saturday morning, depending on how far upstream and how late it forms.

The thermal gradient then advances southwestward as a backdoor cold front on Saturday allowing temperatures to return to near average this weekend, perhaps even a bit below average.

AVIATION (00Z TAF Issuance)

Issued at 739 PM EDT Wed Sep 2 2026

Impacts:

- Low chances of MVFR visibility in fog/BR late tonight, mainly KLAF - West-southwest gusts Thursday afternoon up to 13-17KT - VCSH possible at KLAF after 21Z Wednesday

Discussion:

VFR conditions to generally prevail near central Indiana terminals through early Thursday evening as broad, stacked subtropical ridge continues to drift east over much of the CONUS. Overall conditions a near carbon-copy of preceding 24 hours, so have added TEMPO for MVFR/ VFR fog at KLAF 08Z-12Z Thursday and noted slightly higher gusts for Thursday afternoon where 15-17KT gusts will be possible at times for at least KIND/KLAF.

Otherwise expect occasional cirrus and perhaps a bit better coverage of afternoon cumulus Thursday. Isolated convective showers are possible late in the 24/30-hour period, mainly at KIND/KLAF, but confidence too low to include in TAFs at this time. Light southwest winds to become variable by late tonight...with slight overall veer in heading for Thursday to mainly 230-260 degrees, often sustained near 10KT at KIND and near 7KT elsewhere.

IND WATCHES/WARNINGS/ADVISORIES

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