textproduct: Indianapolis

KEY MESSAGES

- Severe storms and locally heavy rain possible again this afternoon and evening, with damaging winds and localized flooding the primary concerns

- Cooler mid week with a brief break from rain chances, before showers and storms return to the forecast late week into the holiday weekend

FORECAST UPDATE

Issued at 950 AM EDT Tue May 19 2026

Satellite imagery shows clearing across central Indiana with signs of a remnant outflow boundary from upstream convection last night. Thicker overcast skies are found to the west of this outflow boundary, slowly moving eastward this morning. There should be a couple of hours of efficient solar insolation this morning before these clouds arrive. High-resolution guidance that shows the clearing well also depicts rapid destabilization (to between 1500- 2500 J/Kg MLCAPE) through this period. As such, renewed convective activity appears likely again this afternoon.

In terms of hazards, RAP soundings indicate that some mid-level dry air may be present today. Shear is modest, under 25 knots on average. However, steep lapse rates and DCAPE values around 1000 J/Kg could lead to downbursts and efficient cold pool production. The 25 knots of shear may also be enough to allow for loose organization into multicell clusters. Therefore, strong to damaging wind gusts are possible with storms today.

The wind threat diminishes after sunset as the column moistens and lapse rates weaken slightly. RAP soundings show the atmosphere becoming more efficient for rainfall production overnight (deep warm cloud layer, saturation to the EL, and moist adiabatic lapse rates). A cold front sagging south across Indiana will interact with an MCV approaching from the southwest, prolonging large-scale lift tonight. Most guidance is on board with showers and thunderstorms continuing on and off through the night. There is a signal for heavy rain within most guidance with pockets of 1 to 3 inches across the southern half of our area. QPF coverage in guidance isn't as widespread as yesterday, but these pockets tend to line up where the heaviest rain fell. Additional flooding may be possible tonight and trends will need to be monitored closely.

DISCUSSION (Today through Monday)

Issued at 342 AM EDT Tue May 19 2026

Today and Tonight -

Quiet but mostly cloudy conditions are expected early this morning. The rapidly weakening northern extent of a line of showers currently over western Illinois will move into the area this morning and may produce some light rain in spots, though somewhat more substantial rain and thunderstorm chances will wait until later in the day when the cold front approaches the region.

Ample instability and modest deep layer shear will exist to promote organization of developing convection this afternoon, and at least a localized severe threat, primarily driven by wind, will exist. This threat will persist into the evening hours when the front pushes through.

Hydrologic concerns, particularly given precipitable water values near the top end of climatology and widespread significant rainfall yesterday of 1.5 to 3+ inches, will be at least an equal concern to the severe threat, with flash flood guidance values as low as three quarters of an inch in one hour across central Indiana. HREF probability matched means indicate at least a low chance of reaching these amounts in a few areas through tonight, though perhaps not quite enough for another flood watch.

Wednesday through Monday -

Once the front has pushed south of the area, it will stall out a bit, though high pressure passing through the Great Lakes in its wake will keep it suppressed to the south and allow for both a brief cooldown and a break in precip chances from late Wednesday into Thursday evening.

Rain chances return late week into early next week as a large upper level low swings through the northern tier of the country and pulls a warmer and moist airmass back into the area, though chances with the exception of Friday will be low for the time being given significant model inconsistencies and resulting uncertainty.

AVIATION (12Z TAF Issuance)

Issued at 653 AM EDT Tue May 19 2026

Impacts:

- Wind gusts Tuesday 20-27KT

- Showers and thunderstorms possible late this afternoon into this evening

Discussion:

A few showers or isolated storms are present over north central Indiana this morning, which will necessitate some VCSH early in the period.

Winds will strengthen as mixing ramps up Tuesday morning, with gusts of 20-27KT likely through the day, generally from 210-230 degrees.

Showers and thunderstorms will be possible late in the day as a cold front approaches and passes through the area. Winds with frontal passage will veer to westerly and northwesterly late in the period, with gusts ending in typical diurnal fashion this evening.

Ceilings post frontal will likely drop into MVFR, though some IFR cannot be entirely ruled out. Later packages will refine this.

IND WATCHES/WARNINGS/ADVISORIES

None.