textproduct: Indianapolis

KEY MESSAGES

- Sunny and Warmer on Tuesday.

- Brief return of heat midweek with a chance of storms Late Wednesday Afternoon into Thursday.

FORECAST UPDATE

Issued at 937 PM EDT Mon Sep 7 2026

The overall airmass will begin to shift overnight as wings veer from NE to SE. In return, moderate moisture advection is expected to occur. This setup along with some subsidence aloft typically leads to valley fog in areas more sheltered from any gradient wind. For this reason, patchy fog has been added for most of the mid-Wabash River Valley.

No other major changes have been made to the ongoing foreacst.

DISCUSSION (This evening through Monday)

Issued at 227 PM EDT Mon Sep 7 2026

Surface analysis this afternoon shows strong high pressure in place over Lake Huron, providing easterly surface flow to Central Indiana. Aloft, strong ridging was in place over the upper midwest, resulting in NW flow across Indiana. Water Vapor imagery shows subsidence in place across Indiana and OH. Dew points were in the 50s as mixing has produced lower values. GOES19 shows mostly sunny skies across the area.

Tonight and Tuesday...

The upper ridging over the northern plains states will push east to the eastern Great Lakes tonight and Tuesday, keeping any forcing dynamics well north of Central Indiana. The strong surface high pressure will drift SE to the middle Atlantic states by Tuesday, but continue to maintain control of our weather. Forecast soundings and time heights show a dry column with subsidence in place through Tuesday. Dew point depressions tonight may be small, resulting in patchy fog, especially in rural areas.

On Tuesday a mid level inversion appears to remain in place, and this should again prevent much in the way of CU development, resulting in another mostly sunny day. Temperatures will be warmer, as southerly flow will develop allowing warm air advection. Look for Highs to reach the middle and upper 80s

Wednesday...

The upper ridging across the area will have broken down to a progressive, nearly zonal, flow across the northern CONUS by Wednesday. A short wave within this flow will be pushing across southern Canada through the day, keeping the best forcing dynamics there. Within the lower levels the tail of an associated cold front will be pushing across the Upper midwest and central Plains. Upper forcing along the tail of the front is limited. However, southerly flow ahead of the front streaming into Indiana will allow for an even warmer and more humid air mass to arrive. Dew points will surge into the 60s. Forecast soundings by late afternoon show diurnal convection possible with marginal CAPE available. Thus will keep things dry through 18Z, but afterward due to diurnal heating and instability, chance pops for showers and storms will be included, into the evening hours. Look for highs in the lower 90s.

Thursday...

With upper flow nearly parallel to a surface front early on Thursday, chances for rain will continue, especially south. An upper impulse should finally push the front south by early Thursday night.

Locally heavy rain will be a threat with precipitable water values over 2 inches and the potential for training storms (with the slow movement of the front).

Clouds/rain will keep temperatures cooler with highs around 80 for most areas.

Friday and beyond...

Uncertainty rises in this period. The upper ridge to the southwest will try and increase its influence over central Indiana. Meanwhile, upper waves moving through the flow to the northeast of the ridge will try to keep the ridge away and bring rain chances to the area.

For now, believe the best chances for rain will be on Saturday, but that may change. Temperatures will begin to increase again as the ridge attempts to build northeast, but readings should remain below 90 for the most part.

AVIATION (00Z TAF Issuance)

Issued at 653 PM EDT Mon Sep 7 2026

Impacts:

- Fog likely at KLAF early this morning.

Discussion:

High pressure to the northeast will push to the southeast through the TAF period. This will shift winds from out of the east to southerly by tomorrow morning. Subsidence from this high pressure will keep conditions dry, with strong diurnal cooling and winds weakening overnight. This will likely allow for patchy fog overnight, primarily near KLAF.

Tomorrow, winds should stay out of the south, with occasional gusts between 11-15kt. Left gusts out for now, but a tempo group will likely be needed in the afternoon.

IND WATCHES/WARNINGS/ADVISORIES

None.