textproduct: Indianapolis

KEY MESSAGES

- Strong post-frontal northwest winds will gust between 30 and 40 mph Friday morning and afternoon

- Widespread frost likely late Saturday night and Sunday morning.

DISCUSSION (Today through Thursday)

Issued at 124 AM EDT Fri Oct 16 2026

Current Weather through Friday:

The Ohio Valley will be going through a significant pattern change over the next 24 hours as a mature low pressure system continues to push eastward within an amplified positively tilted upper level trough. The orientation of this trough created a less aligned phasing of the mid to lower level low of which has created a multitude of weaker boundaries out ahead of the primary cold front and a slower arrival of polar air. One of these confluence boundaries was the initiation point for a broken line of strong to severe thunderstorms this afternoon and evening. As of 04Z, this line has weekend significantly with only scattered showers remaining over far E/SE Indiana.

Another area of low level confluence can be observed over NW Indiana and E Illinois, of which will be the source for additional showers and isolated weak thunderstorms tonight into tomorrow morning. Lapse rates within this sector of the low are weak in the mid levels of which should keep convective tops capped below 15kft and the thunder threat very isolated.

The surface low will continue to mature overnight within strong upper level jet dynamics. In return, CAA will continue to increase pushing the cold front quickly E/SE passing through central Indiana between 09-13Z. A few showers will be possible along the frontal passage, but any additional QPF should be less than 0.1".

For the remainder of the day, central Indiana will be within a much cooler airmass with dew points in the 40s and high temperatures in the mid to upper 50s. Modest lapse rates up to 850mb will likely lead to efficient PBL mixing in the afternoon with gusts upwards of 40 MPH. A few isolated showers cannot be ruled out as saturation at the top of the PBL remains coincided with the previously mentioned steep low level lapse rates; that said, any QPF will be minimal. As the late afternoon and evening approaches, mean low level winds back towards 330-360 degrees, of which provides an efficient fetch across Lake Michigan. While a majority of any lake effect rain showers will likely remain north of central Indiana, isolated to scattered showers over NW portions of the area will remain possible from 21- 01Z.

Friday Night through Sunday Morning:

The remainder of the forecast period will become rather stagnant as the upper low associated with today's trough passage will detach from the flow and become cutoff over the Eastern Coast. This in combination with a weak split flow upper jet will keep low level conditions fairly similar through the weekend and into next week. While the bulk of the forecast will remain similar, slight fluctuations in surface pressure over the next 5-7 days will still lead to slightly different temperatures and wind speed/direction over the forecast period.

Continued CAA Friday night will lead to cold morning lows Saturday morning, but there is some uncertainty on the extent of any frost given consistent 6+ MPH surface winds and marginal temperatures around 36-38 degrees. Greatest chances will be within sheltered areas in NE portions of central Indiana, but likelihood of occurrence is currently below 50%. The aforementioned strong CAA will lead to height rises beneath 850mb and therefor building high pressure Friday night through most of Saturday. The centroid of this surface high is expected to overlap with the core of the mid level polar airmass late Saturday though Saturday night leading to our coldest temperatures of the season. Frost looks definite for most of central Indiana on Sunday morning, but there is still some significant uncertainty in below freezing temperatures. Much of this will depend on the timing of the surface high passage along with how it faces with the 850mb temperatures. Ensemble probabilities indicate greater around a 50% chance for NE/E portions of the area, which will be the focus for any freeze headlines in later updates.

Remainder of Sunday through Wednesday:

The anticyclone will drift eastward toward the Mid-Atlantic on Sunday, allowing insolation to rebound highs into the upper 50s and lower 60s. Lows Sunday night will remain cool, in the upper 30s to lower 40s, with patchy frost confined to far eastern rural valleys before low-level winds back to the south.

For Monday through Wednesday, the synoptic pattern transitions as upper-level ridging builds over the eastern states and a deep trough carves out over the western CONUS. Steady south-southwesterly return flow will drive a significant warm air advection regime across the Ohio Valley. 850 mb temperatures will moderate to +10C to +13C, pushing daytime highs into the upper 60s and lower 70s by early next week. Overnight lows will moderate into the upper 40s to mid-50s.

Long range guidance generally supports quiet weather conditions persisting through the middle of next week as surface high pressure remains in control. Return flow should continue to provide a gradual moderation in temperatures.

AVIATION (06Z TAF Issuance)

Issued at 106 AM EDT Fri Oct 16 2026

Impacts:

- MVFR ceilings 07Z-19Z - Wind shifts to NW early in the period. - Wind gusts to 30kt after 15Z.

Discussion:

Much of the area is within a brief period of VFR between two weak confluence boundaries. A cold front will quickly push to the E/SE tonight shifting winds from SW to NE.

Cold air advection and trapped lower level moisture will provide MVFR cigs across Central Indiana later tonight through 15Z, with some lifting likely within diurnal heating in the afternoon. Winds will be brisk after frontal passage, sustained between 12-15kt with gusts nearing 30kt after 15Z.

Friday night, winds will shift towards northerly with gusts waning. Scattered showers will be possible at KLAF.

IND WATCHES/WARNINGS/ADVISORIES

None.