textproduct: Indianapolis

KEY MESSAGES

- Another round of storms expected this evening into the early overnight

- Damaging winds and tornadoes are the main threats with large hail also possible

- Flood Watch through 2AM with rain amounts locally as high as 4 inches

- Below normal temperatures will continue for much of the period

FORECAST UPDATE

Issued at 1006 PM EDT Wed Jun 17 2026

In terms of the forecast, only a few changes were needed. First was temperatures so that they match observations better as the north has cooled off while across the south is still on the warmer side. Next was to update the PoPs and clear out our NW from much of the showers and storms as they have pushed south.

As of 10pm, severe weather is ongoing with numerous strong storms and even a tornado warning in effect. Storms will continue to drift ESE as the night goes on and should weaken or move out by around or shortly after 2am. Continue to monitor warnings.

MESOSCALE UPDATE

Issued at 730 PM EDT Wed Jun 17 2026

Surface mesoanalysis shows strongest pressure falls are located across central Indiana with between 3-4 mb/2 hr. This is collocated with the core of the 50-60 kt 850 mb jet per objective analysis and recent IND VWP data. Thanks to locally backed low level flow and moderately strong 700 mb flow, strong low level shear currently exists across the region. An incredible 0-1 KM SRH from 700-800 M2/S2 and 0-3 KM SRH around 1200 M2/S2 has been noted recently on VWP data.

So far the main limiting factors for a more significant tornado threat across IL/IN with ongoing convection is substantial mid level warming (700 mb temps around 10 C per STL ACARS sounding) combined with modest surface based convective inhibition leading to weak 0-3 KM lapse rates under 6 C/KM, modest instability /1000-1500 MUCAPE/ and 50-100 J/KG OF MU/SBCINH/. The existence of this mid level warming with forced ascent through the inhibition layer centered from 850-700 mb combined with the strong 0-3 km shear has been confirmed from recent storm chaser video feeds showing a classic large base with laminar shape and limited low level vertical motion/vorticity generation.

Continued low level moistening with dewpts rising into the lower 70s per downstream obs in southern MO/IL combined with slight mid level cooling (likely reason for renewed CI over wcentral IL) should support a increasing surface based storm threat in the next 1-3 hrs. Therefore there still remains a significant tornado threat, as low level shear will remain near current values through 11 PM EDT before gradually weakening from the west. The significant tornado threat will include all of central Indiana, with the likelihood for scattered very large hail and damaging winds gusts.

DISCUSSION (This evening through Wednesday)

Issued at 148 PM EDT Wed Jun 17 2026

Overview.

A widespread and significant severe weather outbreak is expected for today with the first round of mostly sub-severe storms moving through Indiana and western Illinois at this time. Expectations are for a second round of severe storms towards the evening and early overnight hours with the threat for damaging winds, tornadoes, large hail, and flash flooding. The threat for higher-end tornadoes will be dependent on how long storms remain discrete, which currently looks likely through at least Illinois and portions of western Indiana. Flash flooding will also become a concern, especially towards southern Indiana as the convective line slows.

Following tonight, the pattern will transition toward a quieter and more stable state. While lingering moisture may cause some cloudiness early Thursday, the overall trend through the remainder of the week and into early next week is quiet with high pressure and seasonal temperatures.

Rest of Today.

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 12Z 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.

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.

Outside of the severe weather, both flooding and strong gradient winds will be a concern with the gradient wind threat mainly through 00Z and the flooding threat mainly associated with the second round of convection. HREF PMMs show pockets of 4+ inches with some uncertainty as to where the axis of heaviest rain will fall. Confidence is currently highest across southern Indiana but with the uncertainty, we plan on issuing a flood watch through the entire forecast area, especially considering the very heavy rains so far this June.

Thursday through Saturday.

As the potent cold front responsible for the Wednesday storms pushes well to our east, a deep, dry northwesterly flow will become established across the Ohio Valley. On Thursday, any lingering cloud cover from the overnight period will quickly scatter and dissipate, giving way to abundant sunshine. Model guidance shows a noticeable drop in dew points throughout the day, leading to a very comfortable afternoon with high temperatures in the lower to middle 70s.

Friday and Saturday will feature pleasant early-summer weather with a surface high-pressure system tracking across the Great Lakes and into the Ohio Valley. This system will suppress any potential for convective development, ensuring clear to mostly sunny skies and light, variable winds. With the lack of any significant forcing mechanisms and a very dry air column, the forecast remains dry with high confidence. Daytime temperatures will be pleasant, ranging from the mid-70s on Friday to near 80 degrees by Saturday, while overnight lows will settle into the cool and refreshing 50s.

Sunday through Wednesday.

The quiet conditions are expected to persist through the second half of the weekend and into the early part of next week. Ensemble guidance remains in strong agreement that an upper-level ridge of high pressure will amplify across the central United States, effectively keeping the pattern dry and stable pattern for Indiana. Sunday will be another beautiful day, with temperatures nudging slightly higher into the low 80s under mostly sunny skies.

Looking toward the beginning of the new work week, this ridge will shift eastward, allowing for a gradual warming trend. By Monday and Tuesday, afternoon highs are expected to reach the mid-80s. While some long-range ensemble members suggest a potential breakdown of the ridge by next Wednesday, the current moisture profile indicates that any return to a more active, unsettled pattern will be delayed until the latter half of the week.

AVIATION (00Z TAF Issuance)

Issued at 752 PM EDT Wed Jun 17 2026

Impacts:

- Showers and thunderstorms this evening and into the overnight. IFR or worse conditions possible at times.

- Wind gusts over 25kt into the early morning hours.

Discussion:

Expect a line of convection moving from the northwest through 06Z. IFR and worse conditions are possible especially in heavier rain, along with severe convection.

Outside of convection winds gusts will be up to 25-35kt likely. Higher gusts possible in stronger storms.

The rest of the period will generally be dry with some breezy conditions, gusts up to 15-20 kts, possible into tomorrow.

IND WATCHES/WARNINGS/ADVISORIES

Flood Watch until 4 AM EDT Thursday for INZ021-028>031-035>049- 051>057-060>065-067>072.