textproduct: Indianapolis

KEY MESSAGES

- Patchy frost possible late tonight in sheltered locations north of Indianapolis

- Widespread frost Saturday night with sub-freezing temps possible

- **Freeze Watch** north and east/southeast of Indianapolis Saturday night into early Sunday morning

FORECAST UPDATE

Issued at 1006 PM EDT Fri Oct 16 2026

Gloomy, at times windy, transition into autumn will be waning through the overnight...as strong, broad, and amplified polar surface high pressure settles over most of the CONUS...with its positively-tilted axis from the southern High Plains to Chicagoland, advancing close enough to central Indiana to drop sustained winds under 10 mph by dawn. At least partial clearing has already begun over the northwestern half of the CWA, with SCT/BKN decks expected to continue west of Lafayette/Crawfordsville from fetch off of Lake Michigan that may allow a stray RW over these few western counties.

Carroll County and vicinity may be in a small area east of these lake clouds, yet near the pre-dawn waning winds...to allow patchy frost in the few most protected areas, although chances/confidence too low for any corresponding headline. Dewpoints continuing to drop into the mid- to upper 30s by 12Z will guide overnight minimum temperatures, expected to range from mid-30s north/east of Marion County...to around 40F across the region's southern-third and in downtown Indianapolis.

Freeze Watch continues for zones north/east/southeast of Indianapolis Saturday night.

DISCUSSION (This evening through Friday)

Issued at 301 PM EDT Fri Oct 16 2026

Cold air advection is ongoing following a cold frontal passage last night. Temperatures have been falling through the daylight hours as northwesterly winds gust to between 20-30 mph. Little additional temperature recovery is anticipated and our highs for the day are likely to have already occurred. Persistent low cloud cover will help today feel quite miserable after the prolonged stretch of warm weather we have seen.

Aloft, a potent but positively-tilted trough is diving in from the north. This feature will steepen lapse rates while propelling a secondary front southward. Lapse rates could steepen even more immediately down wind of Lake Michigan as flow passes over the warmer water, increasing boundary layer temps by a few degrees. A band of scattered showers is likely this evening in conjunction with these features. Best timing brings showers to the Lafayette area around 5-6pm with activity reaching Indy by 7-8pm, and eventually Bloomington by 9-10pm. Shower activity could be briefly heavy, but overall rainfall amounts will be under a tenth of an inch.

Winds are expected to become northerly behind the secondary front. Speeds and gusts are also expected to increase, with gusts this evening between 25 to 35 mph possible. The upper trough departs overnight and a quick reduction in winds appears likely tonight. Guidance is in good agreement showing speeds dropping to under 15 mph by sunrise.

Combined with clearing skies, winds may become calm enough to allow for patchy frost north of Indy overnight mainly in sheltered areas. Overall, our current thinking is winds remain elevated just enough to prevent widespread frost. As such, a Frost Advisory was not issued for tonight. Nevertheless, we introduced the mention of patchy frost in rural areas over the northern parts of our CWA.

As surface high pressure builds in on Saturday, the clearing trend continues with winds becoming calm by sunset. Temperatures likely remain suppressed somewhat due to waning cold air advection. Highs only in the 50s are probable despite a return to sunshine. By Saturday night, ideal radiative cooling conditions will be in place. Temperatures in the 30s are very likely with widespread frost. Northeastern portions of our CWA may even dip into the low 30s or upper 20s. We have issued a Freeze Watch for these northeastern areas Saturday night into Sunday morning. Depending on how the surface high sets up, the Freeze Watch may need to be expanded in further updates.

Similar conditions are likely Sunday night with areas of frost likely, especially in rural locations.

NEXT WEEK

Ensemble guidance is in good agreement showing surface high pressure remaining in place through at least mid next week...possibly even the entire week. Aloft, troughing is replaced by ridging. These two factors point towards a warming trend through next week. The warming should be gradual, as the advective component is not there. Highs rebound into the 70s which is a far cry from the near 90 readings we saw a few days ago.

AVIATION (00Z TAF Issuance)

Issued at 524 PM EDT Fri Oct 16 2026

Impacts:

- MVFR ceilings through tonight. - Wind gusts 20 to 30 knots through 04Z. - Rain showers possible this evening with minimal VIS impacts.

Discussion:

GOES19 imagery shows abundant cold air advection strato CU streaming across Indiana. Radar showing some rain showers within the cyclonic flow streaming toward IND and BMG. A moderate pressure gradient across the area was continuing to allow gusts to 20-25 knts.

As daytime heating is lost this evening and the cyclonic flow lessens, winds will slowly subside and clouds should begin to show some breaks, as seen on upstream on GOES19 over NRN IL and WI. Thus have included some VCSH for the first few hours to account for the approaching showers. Overnight skies will be trended to VFR as strato cu is expected to dissipate as high pressure arrives from the west.

Forecast soundings on Saturday continue to show a dry column as the high pressure system arrives, leading to VFR conditions and lighter winds.

IND WATCHES/WARNINGS/ADVISORIES

Freeze Watch from late Saturday night through Sunday morning for INZ030-031-037>042-048-049-056-057-065.