textproduct: Indianapolis

KEY MESSAGES

- Dry through this evening but smoke and haze will be over the area

- Isolated strong thunderstorms possible late tonight. Locally heavy rain will also be possible.

- Noticeably cooler and less humid for the second half of the week

FORECAST UPDATE

Issued at 1002 PM EDT Mon Jul 20 2026

Seasonable moderate humidity will oversee temperatures continuing to slowly fall through the 70s amid light breezes across central Indiana. Meanwhile overall disorganized convective cluster spanning from Des Moines to much of central Illinois will continue to progress to the south-southeast...although the local region's northwest corner could catch light rain from the cluster's eastern- most extent through midnight. Latest guidance's significant downward trends in coverage and intensity of late-night storms has been reflected in latest grids update...where have kept at least widely-scattered thunder for most zones after 10Z...with perhaps numerous showers by 12Z. Dewpoints \will continue to slowly climb to the low 70s for most locations by daybreak...guiding lows to 69-74 across the region.

DISCUSSION (This evening through Monday)

Issued at 703 PM EDT Mon Jul 20 2026

Surface analysis early this afternoon shows high pressure over NY and PA while a frontal boundary was found over MN and SD, sagging SE. This was resulting in southerly surface flow across Indiana. A convective cluster was found over IA and Nrn IL. GOES19 shows high cloud associated with this drifting SE into NW Indiana along with sct CU development across Central Indiana. Haze remained present in most observations. Aloft the upper flow continued to be dominated by high pressure in place across the central Rockies, which was allowing a stream of Pacific moisture to flow across the NW CONUS across the northern plains and diving southeastward toward the Ohio Valley.

Tonight...Quiet weather is expected this evening as the upper wave over the upper midwest continues to approach. As daytime heating is lost, CU will dissipate this evening leading to partly cloudy skies, but haze and high clouds may still linger.

Overnight, the strong upper wave will dig southward, triggering showers and storms as they pass across Central Indiana. Forecast soundings suggest deep saturation overnight and pwats over 2 inches. CAPE appears relatively marginal while shear values remain high enough that a few severe storms cannot be ruled out. The main threat from any storms will be damaging straight line winds and heavy rain resulting in flooding. Diurnally, these showers and storms will not be passing at favorable time of day for strong convection, so overall confidence is medium. HRRR shows area of showers and storms entering NW Central Indiana by 07-08Z before passing through the Indy metro between 10Z-13Z, and exiting Central Indiana by 14Z-15Z Tuesday. HRRR continues to focus best forcing and storm organization over the northern and eastern parts of the forecast area, and will focus best pops in those locations.

Tuesday afternoon through Wednesday, strong Canadian high pressure over the northern plains will begin to build east into the Great Lakes and Ohio Valley. This will result in cooler northerly flow across Indiana on Tuesday afternoon through Wednesday night. Forecast soundings show strong subsidence and a dry column, which should result in a mostly clear nights and partly cloudy days, with highs only in the middle 70s on Wednesday.

Thursday through Monday...

Dry and cooler weather is mainly expected until Sunday and Monday. Models suggest strong ridging developing aloft over the western CONUS on Thursday, persisting through Sunday. This will result in leeside NW flow spilling from the northern Plains and upper midwest and into the Ohio Valley. At the moment, little in the way of forcing dynamics appear to pass until Sunday and Monday. Best forcing looks to pass on Monday afternoon at this point, but uncertainty with timing at this point will remain high.

Otherwise, we will look for a large surface high pressure system lingering across Indiana on Thursday through Sunday, with subsidence in place from the flow aloft. This Canadian air mass will be much cooler, allowing below normal temperatures as highs will only reach the upper 70s and lower 80s through Saturday.

Warmer and more humid southerly flow will return on Sunday and Monday, adding moisture for the potential of storms at that time as that previously discussed upper wave approaches on Monday.

AVIATION (06Z TAF Issuance)

Issued at 159 AM EDT Tue Jul 21 2026

Impacts:

- Isolated -SHRA possible pre-dawn...with greater chances for TSRA at KIND/KBMG within 15Z-18Z, where MVFR/brief IFR will be possible - Occasional MVFR ceilings possible outside of convection 12Z-18Z - Winds slowly shifting from mainly SW at 09Z...to W by 18Z...to NW by 00Z - Winds gusting 15-21KT 09Z this morning to 01Z this evening

Discussion:

Mainly VFR to prevail over central Indiana terminals through most of the TAF period...with periods of MVFR possible within 12Z-18Z from both lower ceilings and at times scattered convection near KIND/KBMG, as slowly-passing cold front's -SHRA/isolated TSRA and associated lower decks progress from NW to SE.

Winds, outside of any convection, will slowly increase through dawn, with sustained flow of 8-14KT overseeing gradual wind shift from west-southwest at 13Z to west-northwest at 21Z. Winds outside of any convection will gust to 15-21KT at all sites by 12Z...through sundown. Winds to diminish to 3-8KT by 06Z Wednesday.

IND WATCHES/WARNINGS/ADVISORIES

None.