textproduct: Indianapolis

KEY MESSAGES

- Patchy to areas of fog tonight east and south. Locally dense fog possible

- Near record highs Monday and Tuesday

- Periodic showers and thunderstorms for midweek

- Coolest air of the season so far next weekend with growing confidence in a widespread frost Saturday night

FORECAST UPDATE

Issued at 951 PM EDT Sun Oct 11 2026

Low clouds have cleared all of central Indiana with the exception of far eastern Randolph County. Some high clouds were to the west. Winds have lessened to near calm at most areas with a ridge of high pressure nearby.

The combination of the mostly clear skies and light winds has allowed temperatures to fall quickly.

The eastern forecast area will likely have more boundary layer moisture overnight, with not having cleared out much before sunset. The south central forecast area did clear out a little earlier this afternoon, but this area had more rain recently.

Given all of the above, believe that at least patchy fog will develop across the eastern forecast area as well as the south central forecast area. Have left in the fog mention east and expanded it farther to the south and west.

The HRRR has been backing off on the widespread dense fog it was showing earlier. Ensembles show the potential for less than a mile visibility, mainly east. With the HRRR backing off on widespread dense fog, have held off on issuing a Special Weather Statement for fog, but did enhance the wording in the Hazardous Weather Outlook. Will continue to monitor closely.

Otherwise, lowered the low temperatures some based on recent trends in observations.

DISCUSSION (This Evening through Sunday)

Issued at 221 PM EDT Sun Oct 11 2026

The remnants of Hurricane Isaias will move away to the east with upper level ridging set to build in immediately for the early part of the week. This will set the stage for near record breaking warmth Monday and Tuesday. A frontal boundary will move into the area for midweek with periodic rain and storms Tuesday night through Thursday. The coolest air of the season so far will follow for next weekend.

Rest of This Afternoon through Tuesday

The back edge of the stratus deck continues to make slow but steady eastward progress across central Indiana early this afternoon. Skies were mostly sunny in the Wabash Valley with thicker clouds largely confined to areas east of Interstate 69. Temperatures varied widely as a result of the clouds...ranging from the lower 60 in eastern counties to the mid 70s in the lower Wabash Valley.

The departure of the stratus associated with what is left of Isaias will be followed by high pressure and mainly clear skies tonight. With winds becoming near calm...potential exists for patchy fog formation in the predawn hours through daybreak Monday focused primarily over the eastern half of the forecast area. The fog will burn off quickly Monday morning as boundary layer mixing commences.

The arrival and expansion of a broad upper level ridge into the Ohio Valley on Monday will signal an abrupt transition...and the first of several upcoming over the next seven days...as stronger southwest flow develops between a frontal boundary over the upper Midwest and the aforementioned high pressure as it settles along the Gulf coast. Strong warm advection will commence and result in well above normal temperatures for Monday and Tuesday across the region. Highs may flirt with 90 degrees in the Wabash Valley both days. For KIND... record highs of 86 for both Monday and Tuesday will be threatened. The frontal boundary over the Great Lakes will drift south towards the area late Tuesday but any convection is expected to remain to the north through Tuesday evening.

Tuesday Night Through Sunday

An increasingly amplified flow aloft driven first by an upper low over the Rockies and then more significantly by a deepening northern stream trough will flatten the ridge over the Gulf coast while initiating a substantial pattern change for the region late week into next weekend. The aforementioned boundary will remain in a quasi-stationary state over the Ohio Valley midweek before lifting back north Thursday in response to a surface low ejecting out of the Rockies and increased upper jet phasing. Rain with embedded thunderstorms will increase in coverage across the region as a result Wednesday and Thursday as multiple surface waves ride along the boundary. There remains at least some potential for a few stronger storms...especially ahead of a strong cold front Thursday afternoon but the potential for an abundance of clouds and rainfall poses some uncertainty in this prospect. With a deep moisture plume pooling along the front aided in part from remnant moisture from the two eastern Pacific hurricanes...there is the possibility for some locations to see one to two inches by Thursday night.

The cold front will sweep across the region Thursday night and early Friday. In the wake of the frontal passage...the aforementioned upper trough will settle and amplify across much of the eastern half of the country. A much cooler airmass will overspread the region with strong cold advection in place. Highs primarily in the 60s on Friday will remain in the 50s Saturday making for the coolest daytime temperatures experienced in over 5 months. While a lack of boundary layer decoupling may limit frost accrual to sheltered locales Friday night...confidence continues to grow in a widespread frost for much of the area on Saturday night as lows fall into the 30s. Subfreezing temperatures are squarely on the table for some of our normal cool spots as well Saturday night.

AVIATION (00Z TAF Issuance)

Issued at 652 PM EDT Sun Oct 11 2026

Impacts:

- Patchy fog at KIND/KBMG overnight and early Monday - Wind gusts of 15-20kt at KLAF/KHUF Monday afternoon

Discussion:

Lower clouds have exited to the east of the TAF sites, and some cirrus will move in at times tonight and Monday.

Light winds and some lingering moisture in the boundary layer will lead to some fog development overnight. Most fog should be east of the sites, but some shallow fog will likely extend west to KIND and KBMG. If fog gets deep enough, worse conditions may develop at KBMG.

Fog will mix out after sunrise Monday. A tightening pressure gradient along with mixing will produce winds around 10kt and some gusts by Monday afternoon, with most gusts expected at KLAF/KHUF.

IND WATCHES/WARNINGS/ADVISORIES

None.