textproduct: Indianapolis

KEY MESSAGES

- Mostly sunny early this week with warming temperatures.

- Patchy fog possible Monday and Tuesday mornings.

- Dry conditions persist through Wednesday, with the next chance for rain arriving Thursday and then continuing into the weekend.

DISCUSSION (Today through Sunday)

Issued at 253 AM EDT Mon Sep 28 2026

A deep cut off upper-level low currently sits over the Mid-Atlantic with a split flow jet over the Plains. Ridging and surface high pressure prevail over Indiana. Large-scale subsidence will allow clear skies to continue today and tomorrow.

Temperatures will be modulated by boundary layer processes, with a large spread between highs and lows anticipated. Efficient mixing will allow highs to rise above normal into the mid/upper 70s. Lows however will be a bit below normal due to efficient radiative cooling, with values into the 40s.

Light winds from the surface high pressure should create good conditions for patchy fog during the overnights, especially this morning and Tuesday morning. The strong solar insolation will dissipate any fog quite quickly after sunrise. Dew points during the afternoon hours both today and tomorrow are expected to be below guidance, due to efficient boundary layer mixing.

An upper-level trough is moving on shore over southern California, which is expected to move eastward becoming cut off from the polar jet. The low then ingests moisture from Hurricane Polo, while inducing cyclogenesis over eastern Colorado. As suspected in previous updates, guidance has slowed the progression of the upper- low and resulting surface system. Rain chances now begin increasing on Thursday rather than Wednesday. Some members of guidance now show rain arriving as late as Friday.

Surface high pressure slides eastward on Wednesday, allowing winds to become southwesterly. With rainfall delayed a few days, warm air advection and partly sunny skies will bring much warmer temperatures to the region. Highs in the 80s appear likely both Wednesday and Thursday, with some locations over southern Indiana approaching 90. Friday appears cooler due to the aforementioned rainfall finally arriving, with highs in the 60s/low 70s. Should the system slow further, then these may be revised upward with future forecast updates.

Regardless, ensembles show a more progressive pattern developing with the upper-low and its associated cold front pushing eastward over weekend. Cooler than average temperatures follow, with lingering rain chances as the front moves eastward rather slowly. A secondary wave developing along the front is possible, and is shown by a few models. Model consensus diverges considerably so confidence in any one solution is low at this time.

Days 8-14: Ensemble guidance hints at large-scale troughing taking hold and persisting well into October. This would promote an extended period of cooler than normal temperatures.

AVIATION (06Z TAF Issuance)

Issued at 1232 AM EDT Mon Sep 28 2026

Impacts:

- Patchy fog possible at the outlying TAF sites between 08-12Z today

Discussion:

Outside of patchy fog at the outlying TAF sites this morning, VFR conditions are expected. Some guidance hints at broken stratus forming near KLAF late tonight, but not confident enough to include. Will have to watch though as some stratus formed yesterday morning well northeast of the area.

Patchy ground fog will likely develop at the outlying TAF sites between 08-12Z today. Will continue to use a TEMPO for MVFR fog at all but KIND. Brief IFR conditions cannot be ruled out. Additional patchy fog may develop into Tuesday morning, but confidence is not high enough to include at this time.

IND WATCHES/WARNINGS/ADVISORIES

None.