textproduct: Indianapolis

KEY MESSAGES

- Dry weather returns for late week into the weekend.

- Hotter and more humid air arrives Sunday into early next week.

FORECAST UPDATE

Issued at 952 PM EDT Wed Aug 26 2026

Minor adjustments to PoPs to match ongoing radar trends, otherwise the going forecast is in fine shape.

Broken line of convection continues to push south/southeastward, producing sporadic areas of wind damage and heavy rainfall, with slowing of the western extent of the main cluster in the past hour to 90 minutes producing several inches of rain in south central portions of the area.

This activity should be out of the area by about midnight, with focus then shifting toward fog and low cloud potential overnight, particularly in the areas that received the most rain this evening. Weak cold advection in the low levels coupled with lagging drier air and the prior rainfall may produce areas of dense fog and stratus near daybreak Thursday, though uncertainty in extent and timing remains fairly high. Will maintain fog mention in the grids and monitor trends.

DISCUSSION (This evening through Wednesday)

Issued at 216 PM EDT Wed Aug 26 2026

Rest of This Afternoon and Tonight...

Weak lift well ahead of the surface cold front produced isolated showers across the northern forecast area earlier. These have since exited, but the lift continues to produce some clouds across the area. Can't rule out another isolated shower developing through mid-afternoon with this lift.

A line of showers and storms has developed in central Illinois this afternoon. This line is ahead of the surface cold front, which is farther to the northwest in Illinois. Instability continues to increase ahead of this line, with MLCAPE over 1500 J/kg. With some heating and moisture advection to go before the line arrives in central Indiana, the storms should become more numerous and intensify.

The line will move through the area from northwest to southeast late this afternoon through this evening. Decent shear will work with the aforementioned instability to keep a threat of some severe storms around. The primary threats will be damaging winds and large hail. However, isolated tornadoes cannot be ruled out, especially north where shear is best.

After midnight, only the southeast third or so will still see some scattered convection around. Instability will have waned by then, ending the severe threat. By 3 or 4 AM, convection should have exited the area.

Drier air will lag well behind the front, and winds will diminish overnight. This will set up the potential for some fog, especially south where rain will have fallen last.

Lows will generally be in the 60s.

Thursday...

The upper trough will linger across the area on Thursday. Low level moisture will remain. Any fog will lift early in the day, with a scattered to broken cumulus field developing. Some CAMs generate isolated convection Thursday afternoon with some weak forcing from the upper trough. This certainly cannot be ruled out, but for now feel odds are below mentioning in the forecast at this time.

Highs will be in the lower and middle 80s.

Friday through Monday...

An upper high will nudge its way into the area during this period. This will keep the area dry with increasingly warmer temperatures.

Initially dewpoints will be relatively low, but they will increase Sunday into Monday, making conditions more humid to go along with the elevated temperatures.

Highs in the lower to middle 80s on Friday will warm to the middle 80s to lower 90s by Sunday. On Monday, highs could reach the upper 80s to middle 90s. Heat indices may be near 100 degrees on Monday.

Tuesday and beyond...

Uncertainty increases in how much influence the upper high will continue to have across the area. For now, believe it will hang on, so will go dry the vast majority of the area on Tuesday. By Wednesday, it may lose enough influence for isolated convection to develop in the afternoon.

Heat will continue, with highs most likely from near 90 to the middle 90s. Heat indices near 100 would also then be likely.

AVIATION (06Z TAF Issuance)

Issued at 1153 PM EDT Wed Aug 26 2026

Impacts:

- Areas of MVFR fog and/or ceilings possible early this morning; Otherwise VFR.

Discussion:

Thunderstorms have exited south of the TAF sites. The associated cold front was progressing across our state also, with light northwesterly winds arriving in its wake.

GOES19 shows clear skies across the TAF sites, but dew point depressions were already getting quite small. Patchy MVFR fog will be possible overnight as light winds and clear skies will be expected. Any morning fog will quickly burn off as heating resumes.

On Thursday, high pressure to the northwest will build across Central Indiana, allowing for dry weather. Forecast soundings suggest CU development due to to diurnal heating, and this will result in some afternoon VFR Cigs.

IND WATCHES/WARNINGS/ADVISORIES

None.