textproduct: Indianapolis

KEY MESSAGES

- Severe weather is likely most areas today with one round of marginally severe storms in the afternoon and more widespread severe weather towards the evening. All modes of severe weather are possible

- Below normal temperatures will continue for much of the period

FORECAST UPDATE

Issued at 917 AM EDT Wed Jun 17 2026

The synoptic pattern remains highly anomalous for mid-June, characterized by a deep mid-level trough and a robust 130+ kt jet streak translating into the southern Great Lakes. Surface analysis reveals a deepening low to our northwest with an advancing cold front that will serve as the primary focus for convective initiation this evening. High-resolution guidance, including the 06Z and latest HRRR runs, confirms a significant severe weather threat, with a heightened concern for discrete supercellular development across west-central Indiana with the 2nd round of storms. The environment is undergoing a rapid, efficient moisture surge, with dew points already rising into the low 60s towards southwestern Indiana. This influx of high-theta-e air is expected to compensate for any lingering morning cloud cover or convective inhibition, providing sufficient buoyancy for surface-based convection. The 13Z Day 1 outlook expanded the Moderate risk further to the south which looks very reasonable based on the expected location of the warm front.

Of primary meteorological concern is the highly anomalous kinematic environment. Model soundings continue to depict elongated, highly curved low-level hodographs with backed surface winds and nearly 70 kt flow at 1 km, creating an environment favorable for significant, long-lived tornadoes if the cells can remain discrete. Current CAM consensus suggests that west-central Indiana remains the primary corridor for potential tornadogenesis, as storms here will be best positioned to interact with maximized low-level helicity and localized outflow boundaries before upscale growth into a more linear mode occurs. While the potential for discrete, supercellular cells is the immediate priority, the transition to a bowing line segment later this evening brings an increasing risk of destructive straight-line winds, potentially enhanced by wake low development. Flash flooding also remains a secondary but serious hazard, as high PWAT values and potential training of convective elements may lead to rapid, localized rainfall accumulations. The situation remains highly dynamic and warrants close monitoring of convective initiation timing and the exact positioning of the surface warm front as the afternoon progresses.

In the near term, confidence is increasing that the ongoing convection crossing into northwestern Illinois will be able to maintain its intensity as it moves further into Illinois and approaches western Indiana. Timing overall remains fairly similar to previous thoughts with convection arriving as early as 12PM, but more likely closer to 1PM with damaging winds as the main threat. With the strong moisture advection, even if the system holds together better than models show, still think a higher-end severe threat is on the table for later this evening.

..SEVERE WEATHER LIKELY LATER THIS AFTERNOON INTO TONIGHT

Early This Morning...

Patchy fog will continue to develop, mainly across areas that saw rain on Tuesday. Fog may be locally dense.

Today and Tonight...

An anomalously strong system (with many variables exceeding climatological maxima for mid-June) will likely bring severe weather to central Indiana, mainly later this afternoon into the early overnight.

An initial upper wave will develop a complex of thunderstorms across Iowa and Illinois this morning, and this will spread east into central Indiana this afternoon. Increasing southwest winds thanks to a warm front moving north will bring in moisture and instability. With strong wind fields, some severe storms may be possible with this complex this afternoon, especially north near the surface warm front.

The highest PoPs will be across the northern half of the area, where better forcing will exist. The far southern forecast area may remain dry.

The strong wind field will allow a quick recovery behind this first complex. Dewpoints will rise into the 65-70 degree range. Aloft, the 850mb jet will increase to 50-60kt by 21Z. The strong wind fields will continue even farther up, creating very high shear values. As noted by the Storm Prediction Center, 0-3km shear may exceed 60kt.

Given this environment, expect supercells to develop upstream of the forecast area mid to late afternoon, and these will move into the area late afternoon into the evening hours. Some CAMs congeal these into a line, but uncertainty exists on whether this will happen given the strong shear profiles. Regardless, damaging to destructive winds, large hail, and tornadoes (some strong) are all possible with these storms.

Excellent moisture transport with this system will also lead to threat of excessive rainfall and localized flash flooding.

The storms should exit the forecast area to the south in the early overnight hours.

The wind fields will lead to near Wind Advisory criteria for much of central Indiana this afternoon and potentially into early evening. Wind gusts around 40 mph are likely, with some gusts near 45 mph possible.

Highs today will range from the upper 70s in the north where clouds and rain will be more of a factor this afternoon, to the middle 80s south where more sunshine is expected. Lows tonight will be in the 60s.

Thursday into Saturday...

A cold front just south of the area on Thursday may allow a stray shower to reach the extreme southern forecast area. Otherwise, high pressure will build in and provide dry conditions for Friday and Saturday. Some guidance does try to create some light QPF Saturday with an upper wave, but confidence is not high enough to include. Highs will near normal to below normal.

Sunday and Monday...

Models agree that a larger upper wave along with a surface low pressure system will move through the area in this time frame, but they disagree on the timing. Will keep the blended guidance's PoPs for now which peak around Sunday night, but confidence is lower than normal. High temperatures will depend on the timing of the rain, but expect near normal to below normal readings.

Tuesday and Wednesday...

Surface high pressure is expected to dominate in this period. With continued northwest flow aloft, near normal to below normal temperatures look to persist.

AVIATION (12Z TAF Issuance)

Issued at 640 AM EDT Wed Jun 17 2026

Impacts:

- Showers and thunderstorms this afternoon and then again this evening and overnight.

- Wind gusts over 30kt this afternoon. LLWS tonight.

Discussion:

Fog should be gone by or not long after valid time, so didn't put it in the TAFs.

Otherwise, expect a complex of showers and thunderstorms to move east across most sites 18-22Z, followed by a line of convection moving from the northwest from about 23Z-06Z. IFR and worse conditions are possible, along with severe convection.

Outside of convection winds will increase this afternoon with gusts over 30kt likely. These may diminish in the evening, allowing LLWS to exist as strong winds continue aloft.

IND WATCHES/WARNINGS/ADVISORIES

None.