textproduct: Indianapolis

KEY MESSAGES

- A few stronger storms this afternoon and evening with damaging winds as the primary threat

- More widespread showers and storms Thursday

- Warm and humid today, then cooler Thursday and Friday

DISCUSSION (Today through Tuesday)

Issued at 249 AM EDT Wed Sep 9 2026

Upper level ridging will flatten throughout the day today in response to a sharp upper trough traversing through southern Canada. This will enable a frontal boundary to drift into the area late today and move slowly south through Thursday producing chances for showers and storms. The frontal boundary will wash out to the south of the area late week as the ridge aloft flexes back into the Ohio Valley. This will maintain warm temperatures through the weekend and into early next week along with daily chances for scattered storms. A more organized threat for rain and storms will accompany a cold front on Tuesday.

Today through Thursday

The cirrus shield associated with weakening convection over Iowa and western Illinois was expanding across the forecast area early this morning. With light southerly flow and an overall muggy airmass...06Z temperatures remained in the 70s.

Despite the overall downtrend in convective intensity to our northwest early this morning...it is becoming apparent that mid and high level clouds will be more prevalent right out of the gate this morning focused especially across the northern half of the forecast area. What is less clear is whether any of the ongoing activity even as it weakens can make it into the northern Wabash Valley by late morning. With CAMs picking up on the remnant outflow boundary tracking into the area after 15Z...have nudged up precip chances a bit faster than previously thought expanding that through the area into the afternoon and early evening as the outflow progresses to the southeast.

Thermodynamic profiles do support steepening lapse rates up through about 700mb this afternoon but much weaker mid level lapse rates. With deeper shear remaining bottled up to the north...convection will be heavily dependent on available instability and be in a scattered pulse intensity mode as the afternoon progresses. DCAPE values peaking near 1000 j/kg suggest that the strongest elevated cores will be capable of damaging winds via localized downbursts with the greatest potential likely across the southern half of the forecast area where heating through the day will be greatest subsequently leading to better instability. Still though with the lack of shear and deep moisture through the column...expect only an isolated risk for severe storms this afternoon into the early evening before deeper instability is lost. Have pulled highs down a bit from the model blend as the increased cloud cover should keep most areas north of I-70 in the 80s. Where clouds will be less prevalent across southern counties highs should still make it into the 90 to 95 degree range.

There now appears to be a lull in overall convective coverage from mid evening into the overnight as convection diminishes along the remnant outflow. The frontal boundary will slip south into the area tonight but more widespread rain will likely wait to impact the forecast area until closer to daybreak Thursday as 850mb winds increase across the Ohio Valley and a stronger upper level wave approaches from the west. This will set the stage for a mainly cloudy day for much of Thursday with periodic showers and a few storms. Could see up to an inch in some locations across the southern half of the forecast area by Thursday evening. Temperatures will be kept down in the upper 70s and lower 80s.

Thursday Night through Tuesday

Lingering showers will end Thursday night as the cold front shifts south of the area before gradually washing out on Friday as the boundary runs into the ridge over the southeast US. The nearby presence of the remnant moisture plume with the front will contribute to at least a risk for a few showers in the southeast Friday with high pressure over the Great Lakes keeping dry conditions over most of the forecast area. Highs on Friday will be in the lower to mid 80s.

Return flow developing on the back side of the departing high pressure will enable low level moisture to advect further north into the region. An approaching frontal boundary will interact with the moist and unstable airmass and likely generate better diurnal convective coverage again focused especially across the southeast half of the forecast area for both Saturday and Sunday. Highs will recover as well into the mid and upper 80s.

Developing low pressure over the High Plains early next week will shift the boundary north as a warm front by Monday enabling a brief return of a hotter and more humid airmass prior to a cold front sweeping through the region on Tuesday with a better chance at showers and storms. Temperatures will remain warm through much of next week but extended guidance continues to advertise a stronger cold frontal passage for late next week with the first taste of early Fall air to follow about 10 days from now.

AVIATION (12Z TAF Issuance)

Issued at 649 AM EDT Wed Sep 9 2026

Impacts:

- Peak wind gusts around 20kts this afternoon - Scattered convection possible by early afternoon at KLAF and later in the afternoon into the early evening at the other terminals - Additional showers late tonight

Discussion:

Mid and high level clouds will continue to overspread the region through the morning. There remains low confidence with regards to whether the ongoing convection can make it into central Indiana late into the afternoon but model soundings show enough instability present to maintain PROB30s at all of the terminals for expected scattered convection...likely developing in the vicinity of a remnant outflow boundary. Coverage will diminish with the loss of heating through the evening and into the early overnight before more widespread showers expand into the region during the predawn hours. MVFR stratus will accompany the arrival of these showers.

Southwest winds will become gusty through the afternoon as the cold front to the north approaches the region. The front will slide into the area this evening with winds becoming light and variable.

IND WATCHES/WARNINGS/ADVISORIES

None.