textproduct: Indianapolis

KEY MESSAGES

- Marginally severe storms through daybreak along with potential additional flooding

- Flood Watch continues through today with additional strong to severe storms through the day, mainly during the afternoon

- Damaging winds will be the main threat today outside of flooding

- Storm chances continue through the rest of the week, severe weather threat looks lower

DISCUSSION (This evening through Wednesday)

Issued at 249 PM EDT Wed Aug 12 2026

Surface Analysis this afternoon shows a broad surface trough stretching from central IL to across Central Indiana. Convection continued along this trough spreading showers and thunderstorms across much of Central Indiana. Water vapor shows a steady NW flow aloft in place, with an wave over IL, generating convection downstream. Dewpoints remained high, in the 60s as much of the area was under the influence of rain cooled air, however across southwest Central Indiana, dew points were in the 70s, providing very humid conditions along with the best instability.

This afternoon through the overnight...

The Thunderstorm complex over Central Indiana will continue to propagate SE across Central Indiana through the late afternoon hours. Heavy rains may result in additional flooding and severe storms cannot be ruled out. Near 00Z the HRRR progresses this system further SE, exiting Central Indiana as the forcing with upper wave exits. Clouds will remain across the area through the evening with rain cooled air in place.

Overnight as the LLJ resumes, more storm development will be possible, but at this time HRRR is developing storms along the boundary which at that time should be located across southern Central Indiana due to the southward push from today's convection. Thus will focus best pops overnight in those locations. Fog will also be possible overnight due to high dew points, light winds and plenty of lingering lower level moisture.

Thursday and Thursday Night...

More rain chances will be expected on Thursday afternoon and into Thursday night. The persistent NW flow aloft is once again expected to continue across central Indiana. An upper level wave is expected to pass across central Indiana providing forcing through the afternoon hours. The location of the surface trough will be key in best initiation and propagation area. For now, this is suggested to be across southern Central Indiana, but changes can occur overnight. Forecast soundings show shallower CAPE at that time with values only around 1000-1500 J/kg across Central Indiana, but much higher values south of boundary in the warmer and humid air mass. Thus will again use high pops on Thursday afternoon for more showers and storm development given the familiar, favorable set-up in place. Again, best chances for now will be across southern Central Indiana which is the expected location of the surface trough. Flash Flood Watch will be extended.

Friday and Friday Night...

Strong ridging within the upper flow is expected to push east toward Indiana on Friday. This will allow surface warm front to surge across Central Indiana as flow becomes southwesterly. Forecast soundings again on Friday show a nearly saturated column at times, with pwats once again over 2 inches. Again shallow CAPE appears available. Thus again likely pops will be needed from the afternoon and into the evening as the warm front surges northeast across the area and acts as a focus for convection.

Saturday through Sunday Night...

Rain chances will persist on Saturday and Sunday as a warm frontal boundary is suggested to be lingering across Central Indiana. Working against this will be the pattern aloft where upper level ridging will be building across Indiana from the west. This will result in some subsidence within the mid and upper levels. However, diurnal convection cannot be ruled out due to the frontal boundary that will be present across the area on Saturday as a warm front and on Sunday as a cold front crossing Indiana. SW flow ahead of the cold front will result in hot weather on Saturday and again on Sunday with highs in the 90s.

Monday through Wednesday...

Better chances for dry weather and temperatures closer to normal will be expected during this time. Northwest flow is expected to resume across the area on Monday due to upper ridging in place over the Rockies. Little in the way of forcing looks to pass during this time. Meanwhile at the lower levels, stronger Canadian high pressure will be building behind Sunday's cold front on Monday and through the first part of the next work week. This should result in partly cloudy skies and highs in the 80s. Temps will moderate by Wednesday as the surface high drifts farther east and southerly return flow begins.

AVIATION (18Z TAF Issuance)

Issued at 249 PM EDT Wed Aug 12 2026

Impacts:

- Thunderstorms moving across the area through 22Z. Brief MVFR conditions possible with any TSRA that strikes a TAF site.

- Fog development expected tonight, especially near LAF/HUF. Possible MVFR/IFR.

- TSRA return on Thursday after 18Z.

Discussion:

Thunderstorm complex across across Indiana will be passing across HUF and IND near 18Z, then diving south to BMG by 19Z-20Z. MVFR conditions will be possible with any TSRA.

HRRR suggests the convection dives SE and ends this evening. This should lead to some convective debris clouds providing VFR Cigs through the evening and overnight. Fog will be possible overnight, as light winds, high dew points and recent rain provide good conditions for fog development.

Additional convection will be possible after 18Z on Thursday as another upper wave arrives and interacts with the warm and humid air mass across central Indiana.

IND WATCHES/WARNINGS/ADVISORIES

Flood Watch through Thursday evening for INZ021-028>031-035>049- 054>057-063>065-072.

Flood Watch through Thursday evening for INZ051>053-060>062- 069>071.