textproduct: Indianapolis

KEY MESSAGES

- Cooler and less humid today

- Hot and humid conditions returning Tuesday and lasting potentially through late week with highs reaching the 90s

- Periodic thunderstorm chances late Tuesday through the end of the week

DISCUSSION (Today through Sunday)

Issued at 301 AM EDT Mon Sep 14 2026

A brief break from the warmer weather comes today as high pressure in tandem with a quick moving upper trough within the band of westerlies will move into New England by this evening. Upper ridging will expand back north into the Ohio Valley by Tuesday with a resumption of hot and humid conditions through midweek along with a periodic threat for thunderstorms as a frontal boundary becomes quasi-stationary over the lower Great Lakes. The ridge will persist over the southeast U S through the weekend with the front drifting into the area during the second half of the week before retreating back north. Above normal temperatures will continue for much of the period with slightly cooler air holding off until early next week.

Today through Wednesday Night

Clear skies early this morning as Canadian high pressure has taken over across the region. With dewpoints into the 50s and northeast winds...comfortable temperatures at 06Z ranging from the mid 50s to the mid 60s.

The presence of the high as it moves east from the Great Lakes into New England by this evening will produce a brief break from the warmer weather experienced much of the first half of September so far. The heat and humidity however will return in earnest as early as Tuesday with return flow on the back side of the departing high advecting a hot and humid airmass back into central Indiana through midweek.

A notable area of deep subsidence will accompany the high pressure today and pivot across the northeast half of the forecast area. This will aid in a spectacular day highlighted by sunny skies...much lower humidity levels and cooler temperatures. Diurnal cu will be limited to the lower Wabash Valley primarily where afternoon humidity levels will be subtly higher. As mentioned...this is temporary with the hot and humid airmass suppressed to the south drawing back into the area Tuesday as ridging aloft expands into the Ohio Valley Tuesday.

A cold front will track into the Great Lakes and mid Mississippi Valley on Tuesday. A broad area of convection will develop this evening over the upper Midwest aided by a strong low level jet and accompany the boundary as it drifts south into Tuesday morning. There does appear to be potential for convection and remnant cloud debris to make it as far south as the northern Wabash Valley prior to the weakening of the 850mb flow during the morning hours otherwise expect much of the day will be dry for the forecast area. By late day...the remnant outflow boundary from the complex tonight and early Tuesday may serve as a focus for renewed convection within a highly unstable airmass across the northern half of the forecast area. A capping inversion will be present south of Interstate 70 where mainly sunny and hot conditions will persist. Model soundings show steep lapse rates through 700mb with DCAPE values over 1000 j/kg. A lack of BL shear will keep convection pulsating in intensity but stronger cells will carry a damaging wind risk that will last into the evening.

The front will slip into the northern half of the forecast area Tuesday night and Wednesday with the potential for periodic storms overnight Tuesday then again Wednesday afternoon and night as subtle waves aloft ripple through the region. With PWATs in the 1.75 to 2 inch range and ample instability in place...convection will carry a risk for locally heavy rainfall and gusty winds.

Temps...low level thermals today support highs ranging from the mid 70s northeast to the lower 80s in the lower Wabash Valley with comfortable humidity levels. Highs will recover into the low and mid 90s Tuesday with heat indices around 100 degrees in the afternoon. Temperatures for Wednesday are more conditional and are dependent on convective coverage. Have highs ranging from the upper 80s north to mid 90s south but if the boundary can make it further south and there are more clouds and storms...daytime temperatures will end up lower.

Thursday through Sunday

The Ohio Valley will remain in between the strong upper ridge to the south and the band of westerlies to the north...resulting in the frontal boundary retreating back north at the end of the week as heights aloft rise yet again. Convection will largely be isolated and diurnally driven both Thursday and Friday. A sharper upper level wave will track across the northern tier of the country this weekend suppressing the ridge back to our south. Consequently the front will be pulled back south into the forecast area as well with an increase in clouds and scattered convection.

Temperatures will range from the mid 80s to lower 90s for much of the area Thursday through Saturday falling back into the lower and mid 80s as the boundary drops into central Indiana on Sunday.

AVIATION (12Z TAF Issuance)

Issued at 535 AM EDT Mon Sep 14 2026

Impacts:

- None

Discussion:

Mainly clear skies early this morning with high pressure settles over the region. An area of mid level clouds moving east through Illinois should diminish in coverage today as it approaches with a drier airmass across central Indiana. The high will drift east into New England through the day with predominant easterly winds at around 10kts then veer to southeast tonight. Mid and high clouds will remain scattered at best through early Tuesday.

IND WATCHES/WARNINGS/ADVISORIES

None.