textproduct: Indianapolis

KEY MESSAGES

- Storm threat continues through tonight, with locally damaging winds, heavy rain, and rapid onset flash flooding remaining possible

- Heat index values in excess of 100 possible today in southern portions of central Indiana

- Dry and milder weather early in the work week

- Additional storms possible Wednesday

DISCUSSION (Today through Saturday)

Issued at 303 AM EDT Sun Aug 16 2026

THROUGH TONIGHT...

One or more upper level waves, at least partially convectively- enhanced, will traverse the area this morning into tonight, with attendant threats for additional showers and thunderstorms. Modest but sufficient deep layer shear will remain in place, along with ample instability in the continued warm and very moist environment. Areas of low level convergence associated both with surface boundaries and remnant convective outflows will serve as foci for development, but given the complex situation and CAM struggles with placement and consistency run-to-run, confidence is lowered. Localized damaging wind gusts will remain the primary severe threat.

Needless to say, flash flood concerns will remain the most pressing worry, however. HREF local probability matched means suggest a threat for up to a 1-2+ inches of rain with the most intense storms, which will continue to pose a extremely rapid onset flash flood threat, though there is some guidance suggestion that the heavier rainfall threat may be more central and south, which, while still quite wet, is not quite in as rough a shape as areas from Indy metro north and northeast.

MONDAY AND TUESDAY...

An area of surface high pressure will mercifully bring at least a temporary end to the repeated rounds of thunderstorms early in the week, with dry weather and near normal temperatures likely early Monday into Tuesday.

TUESDAY NIGHT INTO WEDNESDAY NIGHT...

Unfortunately, an additional round of thunderstorms appears likely late Tuesday night into Wednesday night as another cold front and upper level wave accompanying a strong jet streak aloft passes through the region. Plentiful moisture will be available, though precipitable water values may be slightly more modest (70-80th percentile climatologically). However, somewhat stronger deep layer shear may be available. Another round of severe storms will certainly be possible, though predictability is greatly limited given the sensitivity to prior rounds of storms and model inconsistencies 4 days out.

That said, even with a couple of days to dry out, flash flood vulnerability will remain quite high in the face of any additional convective rainfall given the extreme antecedent conditions, and we will need to remain vigilant through at least mid week for these concerns.

THURSDAY ONWARD...

Amplification of the upper ridge over the western CONUS and southward displacement of both the frontal zone and deeper moisture by surface high pressure and upper level troughing suggest milder temperatures and mostly dry conditions late week and into the weekend, though some slight chances for showers or storms may linger across the southern portions of central Indiana. It will take quite some time for antecedent conditions to significantly improve, unfortunately, and any additional convective rainfall with periodic frontal passages or upper level waves in the broader cyclonic flow next weekend and into the following week will pose at least modest flash flood threats.

AVIATION (12Z TAF Issuance)

Issued at 727 AM EDT Sun Aug 16 2026

Scattered light showers and a few storms are expected in the region this morning through midday. The most likely locations for brief - TSRA would be HUF/BMG, and will carry some Prob30 -TSRA. At IND/LAF, looking more at just -SHRA. Ceilings should mostly stay VFR with variable mid and upper sky cover. There is a brief window for some MVFR ceilings up at LAF later this afternoon, but overall VFR should mostly prevail. Surface winds today should be steady out of the SW, however may go more W-E later this afternoon. Another thunderstorm complex could arrive later tonight, and have hinted at this with another Prob30 mention at HUF/BMG/IND. Overall confidence is low in the timing/placement of that cluster, so will adjust as necessary with later issuances.

IND WATCHES/WARNINGS/ADVISORIES

None.