textproduct: Indianapolis

KEY MESSAGES

- Heat Advisory through this evening for all of central Indiana except the far NE

- Isolated to scattered thunderstorms will be possible at times through the day

DISCUSSION (Today through Friday)

Issued at 306 AM EDT Sat Sep 5 2026

Broad ridging centered over the Plains will amplify while slowly drifting westward. This allows a trough over the northeastern US to push into the Ohio River Valley, bringing an end to the current heat wave. The ridge, temporarily shunted west, returns next week with renewed heat and humidity. The secondary round of heat does not appear to be as prolonged, with another trough arriving late next week along with a reduction in temperatures. Scattered showers and thunderstorms are possible with both troughs, though chances are generally 40 percent or lower due to limited moisture and forcing.

Today will be another hot one for most of the forecast area remaining in a heat advisory with max heat indices near to above 105. The troughing to the NE is expected to finally creep into the area, which will likely keep highs below 90 degrees for our NE counties. With the trough creeping in, there will be better chances of showers and storms today and into this evening ahead of a backdoor front that will bring a reprieve from the heat for the start of the new week.

As of early this morning, the cold front is draped over northern Indiana and into Ohio, along which a couple lines of thunderstorms have formed. The question for central Indiana is if these storms will reach the forecast area later this morning or if they will stay just outside until later in the day. Also watching radar to see how things play out along gust fronts surging south off of the storms. Atmospheric moisture is modeled to increase today with better lapse rates. With the front acting as an initiating force, our convective chances are a lot better compared to the past couple of days. Still, large-scale mid/upper-level forcing is displaced to the northeast and thus the convective chances are dependent on the front itself.

As mentioned above, still looking at a couple of existing scenarios. First, the front initiates convection during the early to mid- morning hours, which then propagates southwestward into the southwesterly low-level flow ahead of the boundary. This would generally limit severe potential with the primary hazard being heavy rainfall and localized flooding.

Second, the front enters central Indiana dry allowing daytime heating to maximize. Increased instability along the front would help initiate convection during the afternoon, which would propagate southeastward in line with the shear vector. Bulk shear is not excessive, but enough to allow for some storm-scale organization into clusters or small bowing segments. Steeper lapse rates and residual dryness may present a downburst or wind threat.

Behind the long awaited cold front, which should arrive late tonight, will bring cooler and drier air to the area. This airmass will only last a few days before the ridging and heat returns for midweek. Another frontal system should bring a relative dip in temperatures again late week as well as another chance of showers and storms sometime mid to late week.

AVIATION (12Z TAF Issuance)

Issued at 649 AM EDT Sat Sep 5 2026

Impacts:

- Scattered showers and storms today, mainly 18Z to 02Z - Wind shift to northeasterly Saturday evening

Discussion:

VFR conditions expected through the TAF period outside of periods of lowered vsbys during convection and brief patchy fog near LAF this morning. Isolated convection may be around the area late tonight towards LAF or IND towards daybreak this morning but more likely VCSH to start. A gust front may also lead to a shift in wind direction at IND at the start of the period. Additional scattered convection is expected to develop during the afternoon and evening hours with greater coverage compared to Friday. Winds will generally remain westerly through late today before a cold front will shift winds to the northeast towards tonight.

IND WATCHES/WARNINGS/ADVISORIES

Heat Advisory until 8 PM EDT this evening for INZ028>030-035>037- 039-043>048-051>057-060>065-067>072.