textproduct: Indianapolis

KEY MESSAGES

- Hot and humid through at least mid week, with daily chances for showers and storms through the forecast period

- Multiple rounds of severe storms will be possible at times from tonight into Wednesday night with damaging winds, heavy rainfall, and flash flooding the primary threats

DISCUSSION (This evening through Sunday)

Issued at 255 PM EDT Sun Aug 9 2026

Bottom line up front...Repeated rounds of thunderstorms are expected this week. Severe storms are possible into Tuesday, and heavy rain and resultant flooding are possible at least into mid-week.

Rest of This Afternoon into Early Evening...

Generally quiet weather is expected for this period, with very warm to hot and humid conditions.

Weakening convection across central Illinois at the moment should diminish in coverage to less than mentionable by the time it reaches the forecast area. However, will continue to monitor for the need to add an isolated shower mention to portions of the southern two- thirds of the area.

Across the northern third or so, additional convection may develop to the south of the current area from northern Illinois into lower Michigan. Have put slight chance PoPs in to cover this threat. A strong storm with gusty winds cannot be ruled out given the instability, but shear is weak enough that odds for severe look low.

Mid evening into Monday morning...

Focus then turns to the develop of an MCS. An 850mb jet should initiate convection to the northwest of central Indiana, most likely near the old outflow from this afternoon's convection. The MCS will then turn southeast as the 850mb flow veers during the night.

Unfortunately, high uncertainty remains on exactly where this will occur. Given the setup, would believe that the highest chances for rain will be north and east of the forecast area. However, as CAMs show in their forecasts, many solutions are possible. For now, will go high end chance PoPs northeast overnight with lower PoPs elsewhere. As the MCS weakens Monday morning, will have chance PoPs east and lower PoPs west.

With increasing shear and continued good instability, severe storms are possible. Damaging winds will be the primary threat. Heavy rain and resultant localized flooding will also be possible with efficient rainfall processes.

Monday afternoon and night...

Higher uncertainty will exist in this period as some convective development will depend on how tonight's convection evolves, and then the next round will depend on the previous round.

Some upper energy may kick off another complex of storms Monday afternoon, again mainly northeast. Will go with chance PoPs there and lower PoPs elsewhere. Monday night, similar conditions to tonight will ignite another MCS which could move through the area overnight Monday night. This one could be more into the forecast area, so went likely PoPs northeast and lower PoPs elsewhere.

With high instability and decent shear, severe storms will once again be possible. Damaging winds will be the primary threat, but large hail and an isolated tornado cannot be ruled out. Heavy rain will continue to be a threat, and will have to closely watch for heavy rain moving over the same areas multiple times.

Looking at temperatures, if clouds from the morning MCS don't stick around, highs in the upper 80s to lower 90s will occur Monday. With the high dewpoints, heat indices around 100 are possible, especially south.

Tuesday and Wednesday...

Central Indiana will remain in northwest flow aloft, and a surface front will remain in the area. This will keep the stage set for clusters of showers and thunderstorms to move through. Locally heavy rain will remain a threat and will have the potential for falling over the same locations. Instability and shear will combine to keep the possibility of severe storms around, especially Tuesday. Damaging winds look to be the primary severe threat.

However, as is the case with previous days, the devil is in the details. Uncertainty remains on the timing of the thunderstorm clusters as well as how each around will affect the others (in terms of cloud cover impacting instability, leftover boundaries, etc). These will also impact which areas see the best chances for convection as well.

Will have likely PoPs at times through this period. Initially focusing on the northern forecast area, these will gradually shift south into Wednesday night as the surface boundary gradually does the same. Confidence in the specific timing remains low.

Heat will remain a potential threat, mainly Tuesday across the south (the south has initially the lower chances for rain and cloud cover). Heat indices may reach around 100 degrees if rain/clouds hold off. Wednesday's readings may be a few degrees cooler with the increased clouds/rain chances.

Thursday onward...

The surface front will continue to move slowly south, eventually getting south of the forecast area by the weekend. This will allow cooler air to filter in, with highs in the upper 70s to middle 80s Friday into the weekend.

Central Indiana will remain on the periphery of the upper high (which will be to the south of the area by then), so energy moving around the high will keep chances for showers and thunderstorms in the forecast into next weekend.

There remains uncertainty on if the high can push north a bit during next weekend, which would bring warmer temperatures than currently forecast, especially south.

AVIATION (18Z TAF Issuance)

Issued at 1258 PM EDT Sun Aug 9 2026

Impacts:

- Brief MVFR ceilings possible early

- Convection possible mainly overnight into early Monday

- Near LLWS conditions tonight

Discussion:

Scattered to broken cumulus will continue this afternoon, with brief MVFR ceilings possible early before bases lift to above 3000FT. Elevated smoke will persist, and some increase in high clouds is expected into the night.

An isolated thunderstorm cannot be ruled out later this afternoon into early evening mainly at KLAF, but better chances for convection arrive overnight into Monday morning with a potential organized cluster of storms. Confidence is not great in timing or location. Northern sites have higher odds than southern ones. Will use PROB30s for now.

A few gusts near 20kt are possible later this afternoon. Increasing winds aloft will bring near LLWS conditions tonight.

IND WATCHES/WARNINGS/ADVISORIES

None.