textproduct: Indianapolis

KEY MESSAGES

- Warm and dry conditions persist through Friday with daily highs reaching into the mid 70s to low 80s

- Minimum RH values will drop below 30 percent at times through Friday bringing slightly elevated fire danger

- Tropical moisture surging northward will bring increasing chances for rainfall to central Indiana on Sunday

FORECAST UPDATE

Issued at 915 AM EDT Wed Oct 7 2026

Surface analysis late this morning shows a cool front stretching across lower Michigan, northern Illinois and northern MO. GOES19 shows clear skies across the state and along the front. Dew points remained in the 40s. Aloft northwest flow was in place, with only some passing Pacific moisture in place.

The dry cold front will continue to approach Central Indiana this afternoon before it passes this evening. A moderate pressure gradient will allow for gusty winds to around 20 mph this afternoon, providing good mixing and allowing temperatures to rise into the lower 80s. Overall, ongoing forecast remains on track and only minor adjustments needed.

DISCUSSION (Today through Tuesday)

Issued at 133 AM EDT Wed Oct 7 2026

Today Through Thursday.

Surface high pressure centered along the Mid-Atlantic coast and broad mid-level ridging positioned over the eastern third of the CONUS will maintain southwesterly low-level flow across the Ohio Valley through Wednesday. Deep-layer subsidence and low column moisture will keep skies mostly clear. Boundary-layer mixing under full insolation will easily allow afternoon temperatures to warm into the upper 70s, roughly 8 to 10 degrees above normal. HREF ensemble member soundings show strong daytime momentum transfer within the mixed layer, yielding southwesterly surface winds of 10 to 12 mph with occasional gusts up to 18 to 20 mph Wednesday afternoon. This strong mixing will also help to bring lower afternoon dewpoints with min RH values below 40 percent, and locally lower than 30 percent with models often underdoing the afternoon dewpoint drop in this pattern. Lows Wednesday night will drop into the lower 50s under clear skies and light south-southwesterly flow.

On Thursday, a northern stream shortwave trough tracking across the Upper Great Lakes will push a weak, moisture-starved surface trough south across central Indiana. GFS and ECMWF soundings show a persistent layer of dry air in the 850mb to 500mb layer, with forcing for ascent remaining well north of the forecast area. Consequently, the boundary will pass dry with PoPs held under 10%. Winds will veer to the northwest around 10 mph behind the boundary. Minor cold air advection will be largely offset by continued insolation, keeping afternoon high temperatures more towards the upper 70s. High pressure building in from the Upper Midwest Thursday night will allow for efficient radiational cooling, dropping overnight lows into the mid to upper 40s.

Friday Through Tuesday.

Surface high pressure translates eastward across the Great Lakes on Friday, maintaining dry conditions and light east to southeast surface flow across central Indiana. High temperatures will remain mild in the mid 70s under mostly sunny skies, with overnight lows Friday night slightly milder with stronger surface winds helping to keep radiational cooling less efficient.

The primary focus of the extended period continues to be the potential for tropical moisture impacts over the weekend. A mid- level trough over the Central Plains is forecast to interact with tropical moisture associated with Tropical Depression Nine moving north out of the Gulf states. Ensemble and deterministic guidance from the GFS, ECMWF, GEFS, and EPS display strong consensus in developing a broad poleward moisture transport corridor streaming northeastward into the Ohio Valley. Mid-level cloud cover will increase through the day Saturday with high temperatures topping out in the mid 70s. Strong isentropic ascent, coupled with upper-level divergence in the right-rear quadrant of an accelerating jet streak over the Great Lakes, will generate rain across the region beginning late Saturday night through Sunday morning with the main uncertainty being exactly where the tropical remnants will track. NBM and EPS probabilities for 24-hour rainfall exceeding 0.50 inches remain in the 60 to 70 percent range for central and southern portions of the forecast area. Persistent cloudiness and precipitation will hold daytime highs to the upper 60s on Sunday, with lows remaining elevated in the upper 50s.

Rain will taper off late Sunday afternoon into Sunday night as the tropical moisture plume shifts east toward the Appalachian region and the primary trough axis translates east. Subtropical ridging and a broad mid-level dry slot build back over the region on Monday, leading to quick clearing and rebound warming. High temperatures on Monday will climb back into the upper 70s to near 80 under return southwesterly flow. By Tuesday, a secondary northern stream shortwave and associated surface cold front will sweep through the Midwest. Strong cold air advection behind the front will bring cooler weather towards mid-week.

AVIATION (12Z TAF Issuance)

Issued at 545 AM EDT Wed Oct 7 2026

Impacts:

- Southwesterly wind gusts to 20kt from 16Z to 00Z

Discussion:

Outside of passing cirrus with a weak frontal passage this afternoon, skies will be clear through the TAF period with the primary aviation impact being southwesterly wind gusts this afternoon. Gusts will generally be 15-20kt but there could be a few gusts as high as 25kt at times. In the aftermath of the frontal passage, winds will then shift more northwesterly, remaining at 5- 10kt through the overnight into Thursday.

IND WATCHES/WARNINGS/ADVISORIES

None.