textproduct: Indianapolis

KEY MESSAGES

- Hot temperatures will continue at times into Saturday, especially south. Heat indices around 100 again today and Thursday.

- Scattered showers and storms today, but severe storms are not expected

- Shower and storm chances persist for much of the time into next week, with temperatures turning cooler next week

FORECAST UPDATE

Issued at 923 AM EDT Wed Sep 16 2026

A mid to low level trough with a weak low level jet is passing through the region today. Moisture advection within this LLJ is allowing more weakly forced convection and numerous showers with embedded thunder over the northern to mid Wabash Valley. This will continue to push E/NE throughout the morning with most of the I-69 corridor and points to the NW getting rainfall.

The residual airmass across the region will be rather unstable this afternoon and evening as convective temperatures are reached. The primary forcing is likely to be old outflow boundaries, of which will be the main area focus for additional convection later today. Generally speaking, the main hazards for this afternoon remains heavy rainfall and lightning, but a few cores may be large enough for an isolated damaging wind threat.

DISCUSSION (Today through Tuesday)

Issued at 252 AM EDT Wed Sep 16 2026

Early This Morning...

Energy riding around an upper high with help from a surface front has been generating convection from northern Missouri into the northern forecast area. Looking upstream, there may be a brief lull as convection remains just west and north of the area, but more will move in closer to sunrise. Outflow from the convection has reached the I-70 corridor, and this may spark an isolated shower in that area. Will continue with mainly chance PoPs from about I-70 north through 12Z.

Some gusty winds and heavy rain are possible, but odds of severe remain low given lessening instability.

Today...

Some stronger upper energy looks to bring showers and some storms to portions of the northern forecast area after 12Z, so will go with high chance to likely category PoPs there. Will keep chance PoPs south of this area this morning in case outflow is enough to trigger more isolated to scattered convection.

There looks to be less upper support this afternoon for convection, but with various old outflows in the area as well as the surface front, will go with at least slight chance PoPs most areas this afternoon. The far southern area may be far enough from outflow and close enough to the upper high to remain dry. Severe parameters look low enough that severe storms are not expected, but a gusty storm is possible. Locally heavy rain will remain a threat with a moist atmosphere.

Convection/clouds will help keep temperatures cooler across the northern forecast area, so went middle to upper 80s. The central forecast area looks more uncertain thanks to the questions about how much convection will be generated by outflows and the surface front. Will go lower 90s there. The south should still be able to reach the middle 90s. Heat indices will reach around 100 again this afternoon for much of the area.

Tonight and Thursday...

More energy riding around the slowly retreating upper high along with the old surface front will keep chances for convection around, mainly across the northern half of the area. Similar to today, clouds/convection Thursday will keep temperatures cooler north with hot conditions persisting south. Heat indices will remain around 100 south during Thursday afternoon.

Friday and beyond...

The upper high will continue to gradually retreat southwest. The surface front will sink far enough south initially to keep PoPs low on Friday, but it will return north again on Saturday as an upper wave interacts with the front. This will bring more rain chances, mainly north.

After a brief reprieve from heat for many areas Friday, hot conditions return on Saturday as the front moves back north.

Sunday into next week, larger upper waves moving through will keep chances for rain around. Cooler air will filter back into the area, with highs by Tuesday in the upper 70s to middle 80s.

AVIATION (18Z TAF Issuance)

Issued at 121 PM EDT Wed Sep 16 2026

Impacts:

- Thunderstorms are possible at KIND/KHUF and KBMG this afternoon and evening.

- Thunderstorms are expected at KLAF late tonight and possibly again at KIND/KHUF Thu morning.

- MVFR ceilings expected to occur at KLAF towards 12Z Thu.

Discussion:

Convection is anticipated to develop over portions of central IN generally near and south of I-70 over the next few hours along residual outflow boundaries. Convective temps from morning soundings suggested temp near 90 F was sufficient for development and recent ACARS soundings from KIND suggest little inhibition remaining. Recent radar trends are showing the first signs of echoes to the west of KBMG. Have added PROB30s for -TSRA with MVFR vis for BMG/IND/HUF this afternoon into the evening to account for the expected scattered convection.

Overnight, the primary frontal boundary will have shifted northward towards KLAF and northern portions of central IN. With an approaching weak shortwave, thunderstorm activity is expected to be more numerous around KLAF after 06Z as the low level jet increases into the boundary enhancing convergence. There is some chance that this greater coverage of TS will move towards KIND/KHUF by 12Z Thursday and have introduced PROB30 for TSRA for this scenario through 18Z.

There is decent agreement that ceilings will fall overnight with low level cooling and saturation associated with both convective outflow and rainfall further N-NW of central IN. Ceilings are expected to fall into the MVFR range for KLAF towards 12Z with IFR ceilings possible with convection.

IND WATCHES/WARNINGS/ADVISORIES

None.