textproduct: Indianapolis

KEY MESSAGES

- Dry through today but upper level smoke will be over the area

- Growing concern for numerous strong to severe thunderstorms with heavy rainfall late Monday night into Tuesday

- Noticeably cooler and less humid for the second half of the week

DISCUSSION (Today through Sunday)

Issued at 307 AM EDT Mon Jul 20 2026

Hazy conditions from Canadian wildfire smoke is expected again today, although should be at least somewhat less dense than what central Indiana saw yesterday. High pressure across the area will maintain dry conditions throughout the day and expecting highs in the 80s again.

The surface high will push off to the east late in the day and into the overnight hours, with return flow, out of the SW, developing on the backside. This will help to push more of the smoke out of the area.

A low developing across central Canada will track north of the Great Lakes, with the associated cold front tracking across the the region tonight and into tomorrow. Confidence continues to increase in an MCS developing to our northwest and diving towards the region tonight due to this feature.

While there remain differences with respect to the actual evolution and track of a convective cluster, the presence of a surface wave along the boundary will promote an enhancement of speed and directional shear in addition to higher SRH values across the lower Great Lakes. Timing will be a factor in whether severe convection will make it into the forecast area and if so how far, but the greatest risk from an MCS moving into the region will be damaging winds especially if a mature cold pool develops. The orientation and strength of the low level jet in tandem with a rapid influx of deep moisture and PWATS near 2 inches supports heavy rainfall and flooding concerns as well and this may end up being the main impact with the potential of a late night/predawn timing early Tuesday. Rainfall rates will be efficient with the freezing level near 15kft. Still details to be worked out but potential for impactful convection late tonight and early Tuesday continues to grow.

The timing and extent of the overnight/early morning convection will have a direct impact on what takes place during the day Tuesday with the cold front across the area. In the wake of the convective cluster, significant uncertainty exists regarding the degree of destabilization as there is potential for an extended period with leftover cloud debris limiting heating. Considering the kinematic environment, any redeveloping convection along the front would carry an inherent severe risk. The most likely scenario however is that the greatest potential for severe weather will be to the southeast of the forecast area Tuesday afternoon and evening. All hazards will be possible with this redevelopment, but damaging winds pose the greatest threat. Any convection will depart central Indiana late Tuesday evening as broad surface high pressure takes over with a cooler and drier airmass.

The surface high is expected to persist through the end of the week allowing for growing confidence in high temperatures to range from the mid 70s to low 80s and lows down into the 50s for a couple of nights. The cooldown won't last long as models show the high exiting and returning surface flow from the south to southwest with temperatures likely returning to near to above normal.

AVIATION (12Z TAF Issuance)

Issued at 701 AM EDT Mon Jul 20 2026

Impacts:

- Low VFR to MVFR visibilities possible through the day from wildfire smoke/haze

- Storms expected to move in at the end of the period from the north

Discussion:

Widespread haze is expected to continue through much of the period due to wildfire smoke from the upper Midwest and Canadian fires. Visibilities have been fluctuating between MVFR and low end VFR at times, and expect that to continue today.

Winds will start off on the lighter side from the SE and generally shift to the SW by this afternoon. Wind speeds will pick up to around 7 to 12 kt by this afternoon as well.

Storms will start to move in at LAF and IND at the end of the period.

IND WATCHES/WARNINGS/ADVISORIES

None.