textproduct: Indianapolis

KEY MESSAGES

- Peak heat indices around 100 degrees each afternoon through Saturday

- Numerous showers and t-storms expected through this evening with more storms possible late Saturday and late Monday into Tuesday

- Isolated strong to severe thunderstorms are possible Saturday evening, damaging wind gusts are the primary threat

DISCUSSION (This evening through Friday)

Issued at 256 PM EDT Fri Jul 17 2026

This afternoon through Saturday night...

An active pattern is expected with multiple disturbances moving through the region. The first disturbance is moving through later today. Modest ascent from the mid-upper level feature combined with daytime heating of a hot-humid airmass will promote numerous showers and thunderstorms through the evening. At least moderate destabilization has occurred this afternoon with steepening lapse rates.

MLCAPE generally around 2000 to 2500 J/KG and DCAPE values approaching 600 to 800 J/KG suggest the potential for gusty winds in thunderstorms. Most thunderstorms will remain sub-severe given weak deep-layer wind shear and modest DCAPE, but an isolated damaging wind gust cannot be ruled out. Efficient rainfall rates from warm rain processes may also result in localized flooding if any training occurs. Look for convective coverage to quickly decrease around or shortly after sunset due to the loss of daytime heating. A few showers or a stray storm cannot be completely ruled out overnight into Sunday morning with marginal forcing in place.

Additional scattered convection can be expected late Saturday as another shortwave and associated cold front move in from the north. Strong destabilization ahead of the approaching cold front along with modest enhancement of mid-upper level flow could promote isolated severe thunderstorms, primarily across northern portions of central Indiana. Forecast soundings depict around 20-30 kt of effective shear, strong instability with steep low-level lapse rates, and DCAPE values as high as 1000 to 1300 J/KG which support the threat. The primary convective hazard is damaging wind gusts. The severe hail threat will be largely limited by the linear storm mode. The main timing for severe weather potential is from the late afternoon through the early overnight hours.

Sunday into next week...

Long range guidance generally depicts upper ridging and weak surface high pressure building in Sunday behind the departing cold front. This will provide quiet weather with cooler-drier conditions. Guidance then suggest another shortwave approaches late Monday into Tuesday. Exact details remain uncertain with this disturbance due to diverging model solutions.

Increasing mid-upper level flow atop an unstable airmass late Monday into Tuesday may support the potential for severe weather, but the large spread in guidance limits confidence. It is worth noting more significant cold air advection appears likely with this disturbance which favors even cooler and drier conditions towards the middle of next week. Temperatures are expected to cool into the upper 70s to low 80s while dewpoints fall into the 50s to lower 60s.

AVIATION (18Z TAF Issuance)

Issued at 137 PM EDT Fri Jul 17 2026

Impacts:

- Numerous showers and thunderstorms expected through 01Z before coverage quickly decreases.

- Brief MVFR conditions possible with any heavier showers or thunderstorms.

Discussion:

Numerous showers and thunderstorms have developed across central Indiana this afternoon thanks to strong daytime heating of a hot- humid airmass. Expect this to continue through about 01Z before convective coverage quickly decreases. Brief MVFR conditions are possible with any heavier showers or thunderstorms. Predominately VFR conditions are expected overnight, but patchy ground fog cannot be ruled out at the outlying TAF sites.

Winds will be light generally from 200-250 degrees sustained at 3- 8KT today with flow closer to 7-13KT Saturday. Infrequent wind gusts around 17-20 kt are possible on Saturday.

IND WATCHES/WARNINGS/ADVISORIES

None.