textproduct: Indianapolis

KEY MESSAGES

- A few showers are possible late tonight and Saturday. Isolated TS are possible Saturday afternoon generally along the I-70 corridor.

- Widespread rain will be around for Sunday into early Monday, with heavy rain and isolated severe storms possible.

- Below normal temperatures will continue for much of the period.

FORECAST UPDATE

Issued at 1042 PM EDT Fri Jun 19 2026

Updated the forecast to match current observations. There is a chance of scattered light rain during the early morning hours as a weak system pushes through the region. Winds will also continue to weaken through the night before picking back up to around 5-10 mph by tomorrow afternoon.

DISCUSSION (This evening through Friday)

Issued at 331 PM EDT Fri Jun 19 2026

Tonight through Saturday Night...

A shortwave trough over the upper Midwest will move SE along the fringes of the longwave trough over eastern CONUS/Canada into Great Lakes tonight. Associated with this system moderate mid level WAA has aided in moderate FGEN forced bands of light to moderate showers across the Siouxland region. Elevated instability is meager (under 200 j/kg) with generally moist adiabatic mid level lapse rates so no TS is expected. However progressive nature of this shortwave and attendant FGEN forcing should support these showers moving into central Indiana overnight. Granted the paucity of low level moisture should keep it mainly of the sprinkle variety tonight into early Saturday.

With daytime heating and some augmentation of the boundary layer moisture owing to the precip fall from the mid level showers and advection of higher BL moisture from the west, expectation is that there may be another round of showers and possibly isolated TS during Saturday afternoon along and ahead of a weak confluence boundary moving southward in the wake of the mid level shortwave trough. Current forecast soundings from the NAM are much more aggressive in moistening BL moisture with forecast soundings showing around a +13C dewpoint at 850mb. This would generate around 750 J/KG of SBCAPE by 21Z. Believe the drier majority of other model sounding solutions limited surface based CAPE to only a few hundred J/KG seems more likely. As a result only carrying a chance of TS

Any convection should diminish quickly around sunset with loss of daytime heating and negligible forcing.

Sunday and Monday...

A shortwave trough over northern CA will shift eastward into the Rockies by Saturday. Lee cyclogenesis developing ahead of increasing mid level flow over the Rockies will support strong convergence and a significant thunderstorm complex over the central high plains by Saturday night. This cluster is expected to shift eastward into the lower plains by Sunday morning supported by a 30-40 kt llj. Activity is expected to continue to propagate along both synoptic and a mesoscale augmented baroclinic zone extending into eastward from the MS valley into central Indiana. Current indications are that sufficient instability will develop by Sunday afternoon ahead of this system (whether in an MCV decayed state or ongoing strong convection) will support vigorous convection just east of the MS river into central Indiana late in the afternoon lasting into the evening/early overnight. SPC's Marginal Risk for Day 3 seems appropriate given there exists some uncertainty in the timing of convective line/cluster. However, if activity reaches central Indiana slightly faster, than forecast area could easily be upgraded to a Slight or potentially even and enhanced risk with all hazards possible. In addition to the threat for severe weather, PWATs will increase to near climatological 90th+ percentile for late June. As a result, depending on where the baroclinic zone sets up, the potential for heavy rainfall from 2-3 inches is increasingly looking likely into Sunday night. WPC Day 3 Slight Risk for Flash Flood seems very reasonable given above normal soil moisture across most of the area from recent heavy rain events.

Precip will come to an end fairly quickly early Monday owing to the unseasonably strong mid-upper jet across our Latitude. Surface High pressure and residual weak CAA clouds should keep highs in the 70s much below normal of mid 80s for the first day of Summer.

Tuesday and beyond...

Tuesday is expected to be dry and cool with high pressure building southward from the northern Great Lakes. Medium Range guidance suggests that a couple of low amplitude shortwave trough will move across the region from Wednesday into Friday. Confidence in the strength and timing of these systems remains low, so will keep broad brushed lower PoPs.

The continued longwave trough pattern centered over eastern North America will keep temperatures below normal through this period and into early next weekend.

AVIATION (00Z TAF Issuance)

Issued at 810 PM EDT Fri Jun 19 2026

Impacts:

- NW winds above 10 kt to start then becoming light overnight - VCSH tonight early Sat morning

Discussion:

VFR conditions are expected through the period.

Overnight a weak storm system over the upper Midwest will move SE across central Indiana. With this system there will be increasing mid level clouds and scattered very light showers could develop. Carrying VCSH to account for this activity.

For tomorrow, skies will mostly clear out by mid morning with passing of this system. West/Northwest winds will increase by midday to 7-12 kts.

IND WATCHES/WARNINGS/ADVISORIES

None.