textproduct: Indianapolis

KEY MESSAGES

- Scattered to numerous showers and some thunderstorms today, potential for severe weather mainly across north central Indiana

- Severe weather is likely most areas Wednesday with one round of marginally severe storms in the afternoon and more widespread severe weather towards the evening and early overnight

- Below normal temperatures will continue for much of the period

DISCUSSION (This evening through Tuesday)

Issued at 152 PM EDT Tue Jun 16 2026

Overview.

Central Indiana will experience an active weather pattern through Thursday morning, characterized by multiple rounds of thunderstorms and a threat for severe weather. A slight risk for severe storms exists this evening, followed by a more significant and widespread threat on Wednesday. Primary hazards include damaging winds, large hail, and isolated tornadoes. Outside of thunderstorms, gradient winds will be gusty on Wednesday afternoon and evening. Following a cold frontal passage on Thursday morning, precipitation will terminate from north to south. A cooler and drier airmass will settle over the region Friday and persist through the weekend, bringing below-normal temperatures and dry conditions.

Rest of Today Through Thursday.

The synoptic pattern across the Upper Midwest and Ohio Valley is characterized by a deep mid-level trough propagating into the Great Lakes region. Central Indiana resides on the southeastern flank of this feature within an area of strengthening southwesterly low-level flow. Surface analysis indicates a surface low tracking through the western Great Lakes, dragging a trailing cold front across the Upper Mississippi Valley. Ahead of this boundary, a low-level jet is driving modest moisture return into the local area. For this evening and tonight, large-scale ascent and differential cyclonic vorticity advection ahead of a weak embedded shortwave will generate scattered to broken convective line segments migrating from west to east. Model soundings indicate that while boundary-layer moisture recovery is limited, steep mid-level lapse rates and a corridor of MLCAPE up to 1000 J/kg will overlap with 35 to 40 knots of effective bulk shear. This environment will support a semi-discrete to multicell convective mode. Given the linear forcing and straight low-level hodographs, the primary threat through midnight will be damaging wind gusts and hail, with the highest probability concentrated across the northern third of the forecast area where large-scale forcing is maximized. The tornado threat will be greater towards northern Indiana, but with SRH values of 100-150 m^2/s^2 quick spin- ups will be possible. Convective coverage will decrease overnight due to nocturnal stabilization and the departure of the shortwave.

Wednesday introduces a more significant severe weather threat as a secondary, intense shortwave trough pivots around the parent low, inducing rapid surface cyclogenesis across the Midwest. Model consensus and ensemble guidance indicate this intensifying system will push a surface warm front northward into central Indiana during the late morning and early afternoon hours. This boundary will serve as the focus for an initial thunderstorm complex or Mesoscale Convective System (MCS). Strong deep-layer shear and a rapidly destabilizing airmass will allow this initial complex to possess severe capabilities, particularly along and north of the warm front where low-level helicity will be maximized. Damaging straight-line winds and isolated tornadic segments are the primary threats with this initial wave.

High-resolution guidance indicates a brief period of diminished precipitation behind the initial complex, allowing for boundary- layer recovery. Intense low-level wind fields and an intensifying 50- plus knot low-level jet will maintain strong theta-e advection, causing instability to recover as surface dew points rise. By Wednesday evening and into the overnight hours, a powerful secondary round of convection is projected to develop along and ahead of the main advancing cold front. The kinematic environment during this period is anomalously strong, characterized by a 500 mb jet exceeding 60 to 70 knots and elongated, curved low-level hodographs. Deep-layer shear vectors perpendicular to the frontal boundary will favor an initially discrete supercellular storm mode before transitioning into a forward-propagating linear system. All severe hazards remain possible. The tornado threat will be maximized near the remnant warm front or older outflow boundaries across northern portions of the forecast area, though strong background shear maintains a risk statewide. Supercells across the north will also carry a risk for large hail, while upscale linear growth late Wednesday night will transition the primary hazard to widespread damaging straight-line winds. Additionally, the tight synoptic pressure gradient associated with the deepening low will produce non- convective ambient wind gusts up to 40 mph from Wednesday afternoon through Wednesday evening.

By Thursday morning, the primary surface low will move into the eastern Great Lakes, driving the main cold front across the southern portions of central Indiana. The front may linger across the southern tier of counties to maintain a low probability of residual showers and an isolated embedded thunderstorm through midday Thursday. However, strong cold air advection and deep cyclonic northwest flow aloft will overspread the remainder of the area. Post- frontal subsidence and dry air entrainment will rapidly lower precipitable water values and clear skies from north to south. Temperatures on Thursday will reflect this post-frontal regime, with cold air advection limiting daytime highs to the upper 60s and lower 70s Fahrenheit, establishing a below-normal thermal trend that will persist into the upcoming weekend.

Friday through Tuesday...

The upper pattern through this period suggests below normal temperatures with occasional shower and storm chances. Models suggest a WNW flow aloft on Friday. This will persist through Tuesday, blocking any strong heat intrusions from the south. Within this quick flow aloft, several short waves area expected to pass from time to time.

Weak waves looks to pass across the Great Lakes on Friday and Saturday, however best forcing looks to remain north of Central Indiana, and strong high pressure is suggested to remain at the surface, creating a less favorable situation for precipitation.

The best chances for rain will be on Sunday into Monday as better ingredients come together. On Sunday, another upper wave is expected to pass, but this time, a warm front will be approaching from the southwest, allowing more moisture to arrive on Southerly winds. A surface area of low pressure is expected to cross Indiana on Sunday night into Monday. Thus, shower and storm chances will be included with these features present.

Eventually, dry and cool weather will return on Tuesday. This will be due to the departure of the surface low and the arrival of high pressure building across Indiana from the northern plains.

AVIATION (18Z TAF Issuance)

Issued at 110 PM EDT Tue Jun 16 2026

Impacts:

- Active weather expected this TAF period.

- Showers and thunderstorms this afternoon and this evening. More storms on wednesday afternoon.

Discussion:

VFR conditions will be in play for most of the period, however two upper level passing waves will help to generate showers and thunderstorms. A few showers initially on radar near 18Z will quickly push to the east by 21Z. This will then allow the first upper wave of forcing to pass, impacting mainly during the 21Z to 02Z period.

Have used a large VCTS window to account through this.

After dry weather overnight, an MCS over the upper midwest will propagate toward Indiana on Wednesday morning. This will allow a return of chances for light rain with isolated showers and storms. Again, have used another window of VCSH for this chance.

Brief MVFR conditions will be possible with any TSRA that strikes a TAF site.

IND WATCHES/WARNINGS/ADVISORIES

None.