textproduct: Indianapolis

KEY MESSAGES

- Showers and embedded thunderstorms early this morning, especially across the southeast half of central Indiana

- Additional isolated to scattered storms this afternoon

- Scattered storms Sunday afternoon and evening

- Heat returning Tuesday and Wednesday

DISCUSSION (Today through Friday)

Issued at 209 AM EDT Sat Sep 12 2026

An upper level wave will bring scattered showers and embedded thunderstorms this morning focused mainly across the southeast half of central Indiana. Additional isolated storms are possible this afternoon before weak high pressure builds in tonight. After a brief cooldown Monday...upper ridging will expand north into the region through the middle of next week with hot temperatures returning. A cold front will become nearly stationary across the lower Great Lakes before gradually sliding into the Ohio Valley during the second half of next week with increasing chances for showers and thunderstorms.

Today through Monday Night

Clouds were increasing from the southwest early this morning in response to an approaching upper level wave. Convection has been ongoing across the western Tennessee and lower Ohio Valleys since Friday evening and had now advanced into the lower Wabash Valley. 06Z temperatures ranged from the mid 60s north to the mid 70s south.

The upper wave is the primary feature of interest in the near term as it pivots across the region through this afternoon. An organized area of convection will continue to track northeast across the forecast area through daybreak. While storms have had a history of stronger winds across far southwest Indiana...anticipate a gradual decrease in intensity as it lifts northeast through the forecast area with less instability present. The main concern from the storms will be the potential for locally heavy rainfall as PWATS near 2 inches advect into the area and the airmass below 500mb is exceptionally moist. High rainfall rates have already been noted west of KEVV earlier and while a downtrend in convective intensity should lead to diminishing rates...there are likely to be some locations over the lower Wabash Valley and southern parts of the forecast area that see a quick 1 to 2 inches of rain.

The weakening area of convection will move east of the region during the first half of the morning with scattered lighter showers and an expansion of lower stratus enveloping much of the forecast area through midday. As the stratus mixes out into a cu field this afternoon and heating commences...potential is there for isolated convection developing across primarily the eastern half of the forecast area on the back side of the departing upper wave. MUCAPE levels increase to 1000-2000 j/kg with abundant moisture lingering. The convection will shift east by early evening as the upper wave moves away to the east.

Weak high pressure builds in tonight in the wake of the upper wave with cloud coverage diminishing. Could again see patchy fog near daybreak Sunday within the muggy airmass. Sunday will begin dry but the approach of a cold front from the northwest will spread the risk for scattered convection back into the forecast area for the afternoon and evening. A surge of cooler and much drier air will follow in the wake of the frontal passage Sunday night as a strong high pressure builds into the upper Midwest. The high will pivot across the Great Lakes on Monday with an axis of deep subsidence swinging across the area. Return southerly flow will begin to draw moisture back into the region as soon as Monday night with the high shifting into New England. The upper ridge will also progress towards the Ohio Valley setting the stage for a return to a hotter regime for Tuesday and Wednesday.

Temps...Highs today will range from around 80 in eastern parts of the forecast area where clouds and the threat for rain will last much of the day...to the mid 80s in the Wabash Valley. Low level thermals support highs in the low to mid 80s Sunday as well. With the Sunday night frontal passage...MOnday temperatures will pleasant ranging from the mid 70s in the northeast to the lower 80s in the Wabash Valley.

Tuesday through Friday

Return southerly flow will develop on the back side of the departing high quickly on Tuesday as mid level heights rise across the Ohio Valley. Highs will likely warm back into the lower and possibly mid 90s Tuesday and Wednesday as the upper ridge centers over the Tennessee Valley. With a frontal boundary stalled to the north over the Great Lakes...convective risks will be isolated and diurnally driven at best.

A retrogression of the ridge into the Southern Plains by late week will finally enable the front to press south into the region with an increasing threat for scattered convection across the forecast area. The heat will be pushed back south as well with temperatures sliding into the lower and mid 80s by Friday then into the upper 70s next weekend. Extended model guidance has backed off on the arrival of a much cooler airmass into the region perhaps not until the 10 to 14 day range as a more chaotic quasi-zonal flow aloft remains across much of the northern half of the country by next weekend.

AVIATION (06Z TAF Issuance)

Issued at 1235 AM EDT Sat Sep 12 2026

Impacts:

- Scattered to numerous showers with embedded thunder predawn hours to near daybreak, especially at KBMG and KIND - Patchy fog possible predawn hours - MVFR ceilings developing through midday - A few thunderstorms will develop mid to late afternoon

Discussion:

A convective cluster over the lower Ohio Valley will lift northeast into the region over the next several hours. Should see lightning strikes diminish from current levels as it lifts into southern Indiana but still feel short TSRA tempo groups are warranted at KBMG and KIND between 08Z and 11Z. MVFR ceilings will accompany the showers and settle over all but KLAF around or shortly after daybreak as the area of rain shifts away to the northeast. Patchy fog may develop at KLAF in the predawn as well.

Lower clouds will linger into the early afternoon before lifting into a broken VFR cu field. Enough instability will remain for isolated convective development this afternoon on the back side of the departing upper level wave...focused primarily over the eastern half of central Indiana. Any rain threat will end by early evening with skies clearing as weak high pressure builds in tonight.

IND WATCHES/WARNINGS/ADVISORIES

None.