textproduct: Indianapolis

KEY MESSAGES

- Heat Advisory in effect for all of central Indiana from Tuesday afternoon through Thursday evening

- Increasingly hot and humid conditions through the middle of this week. Peak heat index values up to 105 are possible each afternoon Tuesday through Thursday.

- Isolated to scattered thunderstorms will be possible at times late this week through the weekend.

DISCUSSION (This evening through Tuesday)

Issued at 257 PM EDT Tue Sep 1 2026

Deep ridging over the central CONUS will be the predominant driver of our upcoming weather over the next several days. Warm SW flow has pushed temperatures well above normal, with high temperatures in the low to mid 90s through Thursday. This in combination with dew points in the low 70s will push heat index values above 100 each afternoon, prompting a Heat Advisories until 8PM Thursday.

The main source of uncertainty will be the amplitude of the aforementioned ridge over the lower Great Lakes and Ohio Valley. Diabatic processes from upstream convection and upper level water vapor will mitigate pressure rises a bit, keeping the apex of the ridge just north of central Indiana. Confidence in convection on the northern periphery of the ridge is high, but how far south this area of convection reaches is where confidence wanes. Currently the expectation is for a majority of any precipitation tomorrow through Thursday afternoon to remain north of the area, but the margin for error is small. Any rainfall and associated cloud cover that does occur will limit diurnal temperature gains, thus temperature gradients across the state could be significant.

Within the super-geostrphic upper level flow, a short wave is expected to develop late tomorrow through Thursday. As this shortwave dives south into the east Great Lakes, modest lift along the leading edge will likely lead to an area of more organized convection late Thursday through Thursday night. Ensemble spread on where this convection will focus is still high, but generally most members agree on an area from northeast IN through northern OH. The severe threat will be greatest over this area, but parameter spacing is sufficient for damaging wind gusts over central Indiana if enough lift is able reach this far west and initiate convection.

Depending on where diabatic pressure chances occur with the previously mentioned MCS, a weak surface trough may develop near or within central Indiana Thursday night. This area of troughing will likely lead to additional rain and storm chances, but confidence on location is low at this time. A deepening trough over the East Coast, will push the ridge westward towards the end of the week, leading to increased uncertainty this weekend onward as the ridge axis falls west of the area and potential shortwaves increase chances for rain.

AVIATION (18Z TAF Issuance)

Issued at 1253 PM EDT Tue Sep 1 2026

Impacts:

- Wind gusts to 15kt Wednesday afternoon

Discussion:

VFR conditions will continue through the period, with high clouds from time to time. A few cumulus will likely develop over the next few hours, and diminish just before sunset.

Winds will be predominately out of the SW throughout the TAF period. This afternoon sustained winds to 8kt are expected, becoming lighter overnight. Chances for gusts increase tomorrow, with gusts of 15kt likely, potentially even higher at KLAF.

IND WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 8 PM EDT Thursday for INZ021-028>031-035>049- 051>057-060>065-067>072.