Plaincast

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Peak heat indices around 100 degrees each afternoon through Saturday

Greater chance for showers and storms Friday through the first half of the weekend, primarily during the afternoon and evening

Isolated strong to severe thunderstorms are possible Saturday PM, Damaging wind gusts are the primary threat

Discussion

Upper ridging and weak surface high pressure will continue to promote mostly quiet weather for much of the area. The stagnant suppressed airmass has kept hot-humid conditions in place with a Heat Advisory still in effect for north/northeast portions of central Indiana, including the Indianapolis metro, through 8PM EDT today.

Isolated to scattered daily convection has developed across far southwestern counties where deeper moisture is located. Latest observations depict dewpoints well in the 70s in those areas. Slightly lower dewpoints further northeast along with weaker forcing has limited convective development, but isolated showers or a stray thunderstorm cannot be ruled out. Convection will likely dissipate shortly after sunset. Patchy Canadian wildfire smoke may slowly move into far north/northeast portions of the area as light winds turn more northerly into the evening.

A more active pattern is expected with multiple disturbances moving through the region. The first disturbance will move in on Friday supporting higher rain chances. Modest ascent from the mid-upper level feature combined with daytime heating of a hot-humid airmass will promote numerous showers and thunderstorms. Severe weather is not expected, but efficient rainfall rates from warm rain processes could result in localized flooding, especially if any training occurs. Additional scattered convection can be expected late Saturday as another shortwave and associated cold front push through.

Moderate to strong destabilization ahead of the approaching cold front late Saturday 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 knot of effective shear, strong destabilization with steep low-level lapse rates, and DCAPE values as high as 1000 to 1400 J/KG which support the threat. The primary convective hazard is damaging wind gusts. Isolated large hail cannot be ruled out either, but the threat will quickly lessen as upscale growth occurs. The main timing appears to be from the mid afternoon through the early overnight hours.

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 morning. Exact details remain uncertain with this disturbance due to diverging model solutions. It is worth noting guidance suggest more significant cold air advection with this disturbance which favors even cooler and drier conditions towards the middle of next week.