textproduct: Indianapolis

KEY MESSAGES

- Areas of fog through daybreak, locally dense at times, Dense Fog Advisory through 9AM for eastern and southeastern Indiana

- Very warm and sunny weather today and Tuesday, with near record highs in the upper 80s

- A slow-moving cold front will arrive Wednesday, bringing widespread rain and scattered thunderstorms through Thursday night

- Cooler air arrives Friday and persists through the weekend, bringing potential frost Saturday night

FORECAST UPDATE

Issued at 332 AM EDT Mon Oct 12 2026

With fog expanding across eastern Indiana, have issued a Dense Fog Advisory through 9AM. High clouds streaming in from the west should help to limit dense fog coverage across much of western and northwestern Indiana, but expect to see additional expansion of fog through daybreak across the east. Will continue to monitor observational trends and adjust headlines accordingly.

DISCUSSION (Today through Sunday)

Issued at 130 AM EDT Mon Oct 12 2026

Today Through Tuesday.

Areas of fog have developed across much of central Indiana and will continue to spread in coverage through daybreak with clear skies and calm winds across the forecast area. Fog generally remains non-dense but with the increasing coverage, have elected to issue a Special Weather Statement. Will continue to monitor observational trends going forward and will issue a Dense Fog Advisory if conditions warrant.

Strong low-level WAA will overspread the area after daybreak as surface high pressure shifts off the Mid-Atlantic coast and a deepening upper trough moves across the Northern Plains. The tightening regional pressure gradient will drive gusty southwesterly surface winds of 15 to 25 kt across the forecast area. Model soundings show strong boundary layer mixing up to 850 MB, where temperatures reaching 15-17C will support afternoon surface highs in the mid to upper 80s. These values will threaten established record highs at IND (86F) and approach the 90F mark in the Wabash Valley. Deep subsidence and dry mid-level air will maintain sub-0.8 inch PWATs, suppressing cloud cover and keeping conditions clear through Monday night.

On Tuesday, the thermal ridge axis will remain centered over the Ohio Valley ahead of a cold front pushing southward out of the Upper Great Lakes. Deep boundary layer mixing and ongoing southwesterly flow will maintain unseasonable warmth with daytime highs again reaching the upper 80s under mostly sunny skies with another shot at breaking the record at IND. HREF and HRRR component members show moisture transport increasing late Tuesday night along a pre-frontal 40 kt LLJ, raising PWAT values above 1.3 inches across northwestern counties. Low-level convergence along the sagging surface boundary will initiate scattered shower and elevated thunderstorm activity after 06Z Wednesday, while areas further southeast remain dry through the morning hours.

Wednesday Through Saturday.

The surface cold front will decelerate and align parallel to mid- level southwesterly flow across central Indiana Wednesday and Thursday. Ensemble guidance is hinting in a prolonged precipitation event as multiple embedded shortwave impulses traverse the stalled boundary. Strong low-level baroclinic forcing combined with moisture advection drawing Gulf moisture northward will push PWATs above 1.5 inches along the frontal zone, exceeding the 90th percentile for mid- October. Diagnostic soundings indicate elevated MUCAPE between 300- 800 J/kg and 0-6 km bulk shear around 40-50 kt, supporting embedded thunderstorms and efficient rainfall rates along with a lower-end threat for severe weather. Cloud cover, precipitation, and post- frontal CAA north of the boundary will cap Wednesday and Thursday highs in the upper 60s to mid 70s.

A robust upper-level trough will dig into the Eastern CONUS by Thursday night, driving the frontal boundary south into the Tennessee Valley and opening the path for strong CAA. High pressure of Canadian origin will build across the Northern Plains into the Great Lakes. Northwesterly winds will gust as high as 40 mph in the aftermath of the frontal passage as strong pressure gradients remain in place. These stronger winds will relax through the weekend as the high centers over the Ohio Valley. Daytime temperatures will drop to seasonable levels in the mid to upper 60s on Friday, cooling further into the upper 50s and lower 60s on Saturday and Sunday. Clear skies, light winds, and efficient radiational cooling over the weekend will allow overnight lows to fall low to mid 30s with a freeze possible across eastern Indiana and frost likely across all of central Indiana.

AVIATION (12Z TAF Issuance)

Issued at 616 AM EDT Mon Oct 12 2026

Impacts:

- MVFR to briefly IFR fog possible at times through 13Z - Southwesterly wind gusts of 15-20kt at LAF/HUF 15Z to 00Z

Discussion:

Transient fog continues across the terminals, but expect improvement after daybreak as dew point depressions begin to increase. There may be another couple of hours of MVFR to IFR vsbys through 13Z. Cigs will be VFR outside outside of a low chance for shallow stratus through 13Z. Southwesterly winds will occasionally gust up to 15- 20kt at time during the afternoon hours, mainly at LAF and HUF. Winds then will drop back to near calm tonight.

IND WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until 9 AM EDT this morning for INZ040>042- 048-049-054>057-062>065-070>072.