textproduct: Indianapolis

KEY MESSAGES

- Rain and storms chances return tonight and linger into early next week, with greatest chances Thursday and Friday

- Localized flooding will be possible at times from repeated rounds of convection

- A few strong/severe storms are possible this weekend into early next week...with low confidence on exact details

DISCUSSION (This evening through Wednesday)

Issued at 251 PM EDT Wed Aug 5 2026

Broad upper-level troughing currently resides over the northern CONUS with an embedded shortwave over the northern Plains. Weak and elongated surface troughing induced by the shortwave is also located over the northern Plains. A cold front has slowly been moving southward, triggering convection upstream across Iowa and northern Illinois. Though the front has been advancing towards Indiana, it has slowed in its forward progress today.

Guidance is in fairly good agreement showing this front continuing to slow, or even stall, to our west. Multiple rounds of showers and thunderstorms are depicted by CAM guidance, particularly where the nocturnal low-level jet terminates. This places the most likely area of thunderstorm activity far to our west over Missouri into central Illinois. A large complex of thunderstorms is most likely to develop, moving eastward into a dry air mass with little large-scale forcing. As such, weakening is anticipated with any storm complex that tries to enter Indiana from Illinois.

Nevertheless, repeated rounds of convection over Illinois should allow for atmospheric saturation which may enable shower and storm activity to finally advance into Indiana tomorrow morning. Even if it does, it still looks to be in a weakening state and likely just a remnant area of stratiform rain or showers. With little instability and shear, severe weather is not anticipated through Thursday morning.

Renewed thunderstorm activity is possible on Thursday afternoon but a key mitigating factor may be too much to overcome. This would be the lingering cold pool / stabilization from tonight's convective complex. Most guidance is against the idea of afternoon showers and storms on Thursday. However, a few do show development after sunset Thursday evening as the low-level jet tries to kick in to our southwest.

A very similar situation may unfold on Friday with isolated to scattered showers and thunderstorms. Forcing looks minimal, so confidence is fairly low on coverage.

This Weekend Into Next Week

A semi-active period of weather may develop this weekend into next week as ridging over the intermountain west amplifies, displacing the CONUS trough eastward. Northwest flow takes hold over Indiana with a warm and humid air mass at the surface. Repeated rounds of thunderstorm development upstream could propagate southeastward aided by the upper-level flow aloft. Additionally, nightly low-level jet development could allow for convective maintenance downstream. Uncertainty is still high, however, even if the environment is favorable for MCSs (mesoscale convective systems). This is because forcing in this kind of environment can be fairly weak and nebulous. Pin-pointing exactly where thunderstorms will develop can be tricky, and which clusters become the dominant MCS even trickier. Additionally, subsequent convective development depends on how the previous round of convection altered the overall environment.

AVIATION (18Z TAF Issuance)

Issued at 138 PM EDT Wed Aug 5 2026

Impacts:

- Showers and possibly a thunderstorm tonight into Thursday morning.

Discussion:

High pressure has weakened and slid east of Indiana this afternoon. Surface winds are now out of the southwest, though still light around 5kt. Light southwesterly flow will continue, becoming more southerly overnight and perhaps calm in a few locations. Winds return to a more southwesterly direction on Thursday.

Showers and thunderstorms are ongoing over northwestern Illinois as of 18z Wednesday. These should progress slowly eastward today into tonight, weakening with time. Remnant showers are possible near LAF as early as 00z. Elsewhere, precipitation may take its time advancing eastward. The most likely time for precipitation is Thursday morning from 10z to 16z.

Ceilings are expected to remain VFR, but a brief period of MVFR conditions are possible during heavier showers or storms.

IND WATCHES/WARNINGS/ADVISORIES

None.