textproduct: Indianapolis

KEY MESSAGES

- Scattered/numerous showers, few t-storms/downpours arrive today with greater coverage in PM...isolated flooding possible

- Humid and very warm this week...nearly daily rain chances continue through Friday...readings near 90F Wednesday-Thursday

- Late this weekend: slightly milder, lower rain chances

DISCUSSION (Today through Sunday)

Issued at 344 AM EDT Mon Jun 8 2026

Humid and at times rainy midsummer style pattern to continue this week as central Indiana sits south of rather active, yet retracted jet that will maintain generally south-southwesterly flow through at least the mid-week. Near to short term will additionally feature weaker-forced but rather broad short wave upper trough lifting from Middle Mississippi Valley this morning, across Indiana today and tonight. Broad ascent coupled with ribbon of Gulf moisture hosting precipitable water values at times in excess of 2.00 inches through dawn Tuesday will promote scattered to widespread showers and potential for areas of heavy rainfall, especially south/west of Indianapolis.

Held off on any headlines at this time given great confidence in heavy rainfall over southwest and probably south-central zones whose past 11-day rainfall totals are mainly zero to maybe 0.40 inches. Greater flooding concern for NW counties / E-central areas that have picked up mainly 2.00-4.00 inches of rain over past 1-2 days...namely from Lafayette south to I-74 corridor west of Metro (Saturday) and to a lesser extent NE/E of downtown Indianapolis (Sunday). Lower confidence in appreciable additional rainfall through early Tuesday for these areas, with greatest chances of heavy rainfall south of US-36 over to the I-65 corridor.

Previous discussion follows for mid to late week timeframe:

Tuesday...

The upper trough will still be in place over Ohio on Tuesday and models continue to suggest some lingering lower level moisture during the morning hours. This could lead to some very light rain showers as through the morning, particularly across the eastern parts of the forecast area. Much better clearing is expected to arrive by afternoon as the trough axis exits farther east. Forecast soundings at that time suggest a dry column on Tuesday afternoon, but warm temperatures in the upper 80s.

Tuesday Night...

There is low confidence for precipitation on Tuesday Night at the moment. Models are showing sufficient low and mid level saturation overnight as a poorly defined upper wave passes, amid what should be ridging building in the wake of the departed trough. The lower levels appear unorganized also, just depicting warm and humid southerly flow in place. Thus will continue to keep some mention of pops in the forecast due to model trends, but confidence is low.

Wednesday...

More warm and humid SW flow will be in place on Wednesday with little in the way of forcing available other than diurnal heating. Forecast sounding suggest typical afternoon and evening instability showers will be possible given the warm and humid air mass. Will include pops for now. Low confidence.

Thursday and Friday.

The commencement of the long-term period on Thursday and Friday features central Indiana deeply embedded within a progressive, moisture-rich warm sector. Recent global deterministic runs of the GFS and ECMWF, along with support from the GEFS and EPS ensemble means, show a consensus that a stagnant subtropical ridge off the Carolinas will keep the local area under a regime of steady low- level warm air advection and moisture convergence. Boundary layer moisture will be robust for mid-June, with surface dewpoints progged to consistently reach into the upper 60s and lower 70s. Strong diabatic heating operating on this high theta-e airmass will lift afternoon maximum temperatures into the upper 80s and lower 90s on Thursday, yielding highly unstable atmospheric profiles. Soundings show MLCAPE values exceeding 2000 to 2500 J/kg during peak afternoon heating. While mid-level lapse rates remain somewhat modest, the lack of significant convective inhibition means that isolated to scattered pulse-type thunderstorms will easily trigger along any remnant mesoscale outflow boundaries.

A more organized severe weather and heavy rainfall threat materializes by late Thursday into early Friday as a deeper mid- level trough pivots out of the Upper Midwest and pushes a cold front toward central Indiana. This synoptic feature will provide the necessary large-scale dynamic ascent and wind shear to organize the highly unstable environment. Forecast models indicate 0-6 km bulk shear vectors increasing to 35 to 45 knots, shifting the convective mode from unorganized pulse cells into a forward-propagating linear structure or robust multi-cell clusters. Damaging straight-line winds and isolated large hail will be the primary hazards with any severe cores ahead of the front. Furthermore, precipitable water values are projected to climb toward 1.75 to 2.00 inches, which sits well above the 90th percentile for early June. These high moisture profiles indicate extreme precipitation efficiency, and any training convective elements ahead of the slow-moving boundary will pose a localized flash flooding threat, particularly across areas with saturated antecedent soils.

Saturday and Sunday.

A pattern shift then takes place late Friday night into Saturday morning as the surface cold front clears the southern counties of Indiana. Strong anticyclonic building will commence as a sprawling 1024 mb Canadian high pressure system drops southward across the Great Lakes. Robust cold air advection will take hold through Saturday morning, driven by a sharp northwesterly wind shift. Deep- layer subsidence and dry air entrainment will rapidly clear out the tropical moisture plume, forcing precipitable water values down to under 0.75 inches by Saturday afternoon. There are some signs of another system towards Sunday with the Canadian model and its ensembles showing a mesoscale driven system, but confidence is very low at this time, especially considering how far it lies from the other global models.

AVIATION (06Z TAF Issuance)

Issued at 155 AM EDT Mon Jun 8 2026

Impacts:

- MVFR CIGs in scattered -SHRA, arriving SW to NE within 12Z-16Z - Periods of -SHRA/few TSRA through afternoon, isolated downpours possible...with greater coverage of convection expected after 00Z Tuesday - MVFR VIS possible at times, especially after 00Z Tuesday

Discussion:

VFR conditions expected through at least 12Z this morning near central Indiana terminals. Muggy and at times showery pattern will persist into early Tuesday across Midwest...with slow arrival of short wave trough from Illinois today promoting at times numerous -SHRA with isolated +RA/TSRA, especially through the latter half of the TAF period. TSRA most likely this afternoon...with lower TSRA chances Monday evening/overnight while numerous/widespread -SHRA to continue under arrival of short wave. Ceilings likely bouncing between MVFR and VFR at times depending on local proximity of individual showers/convection.

Light surface flow veering slightly through pre-dawn from ESE to SE, with further subtle veering to S expected by 21Z today. Winds sustained at 5-12KT after 14Z today, although gusts outside of lone slightly stronger cells should stay under 18KT through tonight.

IND WATCHES/WARNINGS/ADVISORIES

None.