textproduct: Indianapolis

KEY MESSAGES

- Winds gusting to between 25 and 35 mph this afternoon into tonight.

- Scattered showers mainly late this afternoon into early tonight.

- Patchy frost possible tonight, mainly sheltered locations north of Indy.

- Widespread frost Saturday night with sub-freezing temps possible.

- Freeze Watch issues for northeastern counties Saturday night into Sunday morning.

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 (18Z TAF Issuance)

Issued at 143 PM EDT Fri Oct 16 2026

Impacts:

- MVFR ceilings through tonight. - Wind shift to northerly around 00z. - Wind gusts 20 to 30 knots through 04Z - Periodic rain showers with minimal VIS impacts.

Discussion:

Cold air advection has kept low cloud cover in place today. Ceilings have been oscillating between MVFR and VFR. A trend towards predominant MVFR is anticipated this afternoon into tonight. Clearing is likely on Saturday as high pressure builds in.

A secondary upper-level trough arrives this afternoon bringing renewed rain shower activity. Tempo and Prob30 groups have been introduced to cover the most likely timing of these showers.

Winds have been gusty out of the west-northwest, with average gusts between 20 to 25 knots so far today. A switch to northerly is expected once the upper trough and showers arrive. Northerly winds could be more gusty than today, with gusts pushing 30 knots in places. Winds begin diminishing after about 04z tonight, dropping to less than 10 knots by 12z Saturday morning. A few gusts to 15-20 knots could persist into the day Saturday.

IND WATCHES/WARNINGS/ADVISORIES

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