textproduct: Indianapolis

KEY MESSAGES

- Cooler than average conditions persist today with mostly cloudy skies.

- Clearing skies with a warming trend this weekend.

- Showers and thunderstorms possible late Tuesday through early Thursday.

FORECAST UPDATE

Issued at 1016 PM EDT Thu Sep 24 2026

A few adjustments were made to the forecast to better align with current observations. First was the cloud cover as skies are clearing from the east and have almost reached Indy around 2z. Temperatures were also adjusted as they are quickly dropping under the clear skies, so expecting lows across our east in the mid 40s to near 50. The western half will not see as prominent of an effect of the clearing skies as high clouds are moving in from the west late this evening.

DISCUSSION (This evening through Thursday)

Issued at 149 PM EDT Thu Sep 24 2026

REST OF TODAY AND TONIGHT

The overall synoptic setup remains similar over the area with a surface high over SE Canada and an upper low just to the SE. Cold, moist advection along the cold conveyor belt along with modest subsidence has kept overcast skies over the Ohio Valley for much of the day. There is some mid level dry air working its way into the area this afternoon which has allowed for some mixing and pockets of clearing. That said, broad clearing likely wont arrive until late this evening into the overnight as dry air entrainment increases on the northern end of the upper low occlusion along with high pressure building in from the NE. Clearing will be a slow process, but should gradually move through central between 02Z and 08Z from east to west.

Temperatures overnight will have a modest gradient across the area due to this temporal difference in clearing. Some areas over far NE central Indiana where clearing is expected to begin may have enough diurnal cooling to reach the mid 40s by day break. The rest of the area should see lows near to just above 50. Some models are maintaining cloud cover over the southern Wabash Valley as pressure gains wane with the low moving off to the east. If this occurs, lows may only briefly fall below 60 over W/SW portions of the area. I Surface high pressure, centered over southeastern Canada, has be

FRIDAY THROUGH SUNDAY

For tomorrow, a new broad area of low pressure begins to develop over the Mississippi Valley leading to an additional source of cloud cover over central Indiana. Low clouds are likely to be much less abundant, but upper level cirrus will likely push through the area throughout the day leading to opaque, mostly cloudy skies. There is some uncertainty with how thick the cirrus shield will be, and therefor its impact on high temperatures, generally the expectation is for highs in the low 70s, but areas with thinner cirrus may push into the mid 70s tomorrow afternoon.

High pressure will continue to build within easterly flow tomorrow into the weekend, creating greater subsidence over the area. This should keep the broad region of low pressure to the west, eventually resulting in mostly clear skies over the weekend once cirrus debris leaves the area. Diurnal cumulus is likely over western portions of the area, with gradual temperature gains each day. This will lead to a very seasonal late September weekend across the area. Greater diurnal cooling along with lingering surface moisture Friday night may lead to patchy dense fog, but uncertainty is too high to include at this time.

NEXT WEEK

Guidance is beginning to hint at a potent system developing over the Plains around the Tuesday timeframe. Current ensemble suite generally brings the low center to our northwest, with the trailing cold front passing through Indiana. Uncertainty remains regarding the strength and track of the low, but enough of a signal is present to justify higher PoPs Tuesday night through early Thursday. Thunderstorms are also possible, but deep warm moist advection appears limited despite the system's potential strength. For now, most members of guidance show only low amounts of MLCAPE (under 500 J/Kg). This system resembles a cold-season synoptic low with minimal instability and high shear. So, despite the low MLCAPE, this system still bears watching from a severe weather standpoint.

AVIATION (00Z TAF Issuance)

Issued at 801 PM EDT Thu Sep 24 2026

Impacts:

- MVFR ceilings through first few hours of the period

Discussion:

MVFR ceilings are beginning to lift at the start of the period as clearing start to move into central Indiana from the NE. KHUF and KBMG will likely be the last to clear tonight into tomorrow morning. Additional VFR clouds are expected to move in tomorrow.

Winds should remain out of the NE/ENE throughout the TAF period, mainly between 7-10kt with slight lulls overnight.

IND WATCHES/WARNINGS/ADVISORIES

None.