textproduct: Indianapolis

KEY MESSAGES

- Cooler than average conditions persist today with mostly cloudy skies.

- Drizzle and light rain showers this morning.

- Clearing skies with a warming trend this weekend.

- Showers and thunderstorms possible late Tuesday through early Thursday.

DISCUSSION (Today through Wednesday)

Issued at 253 AM EDT Thu Sep 24 2026

Surface high pressure, centered over southeastern Canada, has been in place for the past few days. An upper-level low passed overhead yesterday, allowing for the surface wind field to gain cyclonic curvature. This has lead to weak lift within the boundary layer, causing stratus trapped beneath an inversion to produce widespread drizzle. Drizzle continues as of this writing (2am), and is expected to persist through the morning hours today.

The upper-level low has moved southeastward towards the Mid- Atlantic, and surface high pressure is beginning to nudge southward in its place. Broad subsidence and dry air is expected to return, causing the low stratus to finally begin to dissipate. This process is likely to be slow, with mainly cloudy skies expected for most of the day today. Due to this, we went below guidance for high temperatures today. Clearing ramps up after sunset, especially east of a Lafayette to Terre Haute line.

Winds become light and variable at times tonight, with perhaps a dominant northeasterly component. Some patchy fog is possible given the moist boundary layer, but renewed dry air advection may mitigate this potential. With clearing skies and light winds, the main effect will be much cooler lows than previous nights. Temperatures in the 40s are possible where clearing is most widespread. In urban areas, lows near 50 are more probable. Along the Illinois state line, cloud cover could persist long enough to keep lows in the 50s.

FRIDAY THROUGH SUNDAY

By Friday, low cloud cover will be gone only to be replaced by high cirrus arriving from the northwest. A frontal system over the plains is expected to generate convection from Texas to North Dakota. Though precipitation remains far to our west, debris cirrus could become quite thick at times Friday as it spreads eastward...thick enough to keep high temperatures suppressed a few degrees. High temperatures returning to the 70s is still the most likely outcome, though we did nudge the forecast down a degree or two from guidance.

High pressure strengthens its grip over the region this weekend, providing enough of a buffer to keep thick cirrus at bay. Some thin cirrus may still try to creep into our western counties, however. Winds retain an east to northeast direction through the weekend, so a rapid warm up is not expected. Nevertheless, increasing sunshine should help temperatures gradually warm both Saturday and Sunday. Highs in the 70s are likely both days.

NEXT WEEK

Guidance is beginning to hint at a potent system developing over the Plains around the Tuesday timeframe. Current ensemble suite generally brings the low center to our northwest, with the trailing cold front passing through Indiana. Uncertainty remains regarding the strength and track of the low, but enough of a signal is present to justify higher PoPs Tuesday night through early Thursday. Thunderstorms are also possible, but deep warm moist advection appears limited despite the system's potential strength. For now, most members of guidance show only low amounts of MLCAPE (under 500 J/Kg). This system resembles a cold-season synoptic low with minimal instability and high shear. So, despite the low MLCAPE, this system still bears watching from a severe weather standpoint.

AVIATION (12Z TAF Issuance)

Issued at 640 AM EDT Thu Sep 24 2026

Impacts:

- MVFR/IFR ceilings through 00z, clearing overnight.

- Patchy drizzle and light rain showers this morning.

Discussion:

Widespread IFR/MVFR stratus with drizzle continues across central Indiana. These conditions are expected to persist through the morning hours, with improvement during the afternoon. Despite the gradual improvement, MVFR ceilings likely remain through 00z.

Surface high pressure builds in from the northeast this evening, which brings large-scale subsidence and dry air back into the region. As such, clearing is expected after 00z. Stratus may persist a bit longer from LAF to HUF since the dry air is arriving from the northeast. Skies become mostly clear for a time tonight before cirrus from a storm system over the Great Plains increases after about 12z Friday.

Winds will be lighter than previous days between 5 to 10 knots as high pressure settles in. A period of light and variable winds is possible overnight.

IND WATCHES/WARNINGS/ADVISORIES

None.