textproduct: Indianapolis

KEY MESSAGES

- Extreme Heat Warning in effect through 8 PM, Heat Advisory afterwards through 9PM Saturday

- Thunderstorm chances will increase after 7PM today with downbursts possible

- Greater storm coverage for Saturday with a lower threat for severe weather; Storms may impact outdoor activities on Saturday afternoon and Saturday Night.

DISCUSSION (This evening through Friday)

Issued at 241 PM EDT Fri Jul 3 2026

Surface analysis early this afternoon shows strong high pressure in place over WVA. Low pressure was found over western KS. Aloft, water vapor showed a strong area of high pressure over the Carolinas and VA, and a tropical plume of moisture was streaming north across TX and OK toward the upper midwest. Indiana was still under the influence of of this strong high pressure system, allowing a stagnant air mass, with very warm temperatures. Within the convective plume, an upper level disturbance over northern Illinois was interacting with the very hot, unstable airmass and convection was developing. Heat Index readings across Central Indiana were reaching the 105-110 range.

Tonight...A few stray thunderstorms will be possible this afternoon and early evening, but this diurnal convection is expected to wane this evening as heating is lost. The upper steering flow across the southern Great Lakes is expected to sag southward overnight as this past weeks/s ridge departs to the east. Although this could allow for some overnight convection across far northwest Central Indiana, it will mainly set the state for the more active weather expected for the next two days. Thus after very isolated storms are gone this evening, mainly partly cloudy skies will be expected with another hit and humid night with dew points still remaining in the 70s.

Saturday and Saturday Night...Mainly dry and humid weather will begin the day. However, models show the upper flow will have sagged south across Central Indiana, and our area will no longer be protected from forcing dynamics by ridging. Models suggest a moderate short wave passing on Saturday Night. There will be little change in the air mass prior to this feature arriving, allowing for a favorable column for storms. CAPE on Saturday afternoon is expected to reach over 2500 J/KG with pwats over 1.75. HRRR suggests widespread late afternoon convective devlopment across central Indiana persisting into the evening hours as the warm, unstable air mass interacts with the passing short wave. Timing of these storms could impacts fireworks displays on Saturday night. Due to the high pwats, torrential rainfall will be possible.

Regarding temperatures, a slightly cooler day will be expected as high clouds from upstream convection may be passing during the morning hours and afternoon convection may limit max heating to the mid 90s.

Sunday and Sunday Night...As we begin Sunday morning, dry weather should be present as we start the day. The warm and humid air mass will still be in place as southwest lower level flow remain due to surface high pressure remaining in place over the Carolinas and weak low pressure north of Indiana. The upper flow will allow yet another short wave to approach Central Indiana from the northwest. Again, forecast soundings appear favorable for convection, with steep lapse rates and favorable CAPE in play. This will once again lead to diurnal afternoon and evening showers and thunderstorms. The upper forcing looks to arrive during the late afternoon and into the evening. This should result in another round of widespread thunderstorms. Severe storms cannot cannot be ruled out and due to the high pwats, again heavy rain will still be in play.

Monday through Friday

The upper ridge axis will retrograde early next week positioning central Indiana on the periphery of an active, progressive northwest flow regime aloft. As a series of low-amplitude shortwave troughs and embedded convective impulses traverse the Great Lakes and Ohio Valley...expect daily opportunities for scattered showers and thunderstorms to continue.

Convective potential remains largely diurnally driven and mesoscale dependent on Monday and Tuesday focusing along residual outflow boundaries. Pulse severe hazards...specifically localized downbursts...will remain a secondary threat but with lower overall coverage as thermodynamics become less intense. Weak surface ridging on Tuesday may actually limit convection to isolated at best.

For the second half of next week...extended ensemble guidance indicates a deeper and more cohesive northern stream shortwave digging out of southern Canada. This feature will push a cold front southward through the region by Thursday with a greater risk for more robust and organized convection. In the wake of this frontal passage, strong Canadian high pressure will overspread the area and introduce a much drier and cooler airmass into the region. This will effectively suppress temperatures and humidity back to near to slightly below seasonal averages by the end of next week into next weekend.

AVIATION (18Z TAF Issuance)

Issued at 104 PM EDT Fri Jul 3 2026

Impacts:

- Isolated TSRA, mainly from through 04Z; otherwise VFR.

Discussion:

VFR conditions will expected through much of this TAF period. Diurnal heating will allow for isolated convection this afternoon and evening as steep lapse rates plentiful CAPE is available. This has led to sct-bkn CU across the area with one storm south of BMG developing.

As heating is lost tonight, any storms will subside, leading to just VFR Conditions.

More storms will be possible on Saturday afternoon, especially across northern Indiana as sagging upper flow there begins to provide forcing combining with the hot, humid, unstable air mass in place.

IND WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning until 8 PM EDT this evening for INZ021- 028>031-035>049-051>057-060>065-067>072.

Heat Advisory from 8 PM this evening to 9 PM EDT Saturday for INZ021-028>031-035>049-051>057-060>065-067>072.