textproduct: Indianapolis

KEY MESSAGES

- Widespread minor/moderate river flooding continues south of I-70

- Locally heavy rainfall is expected late Tuesday into Wednesday, which will exacerbate or prolong ongoing flooding

- Scattered severe storms with all hazards are possible Tuesday night and Wednesday

- Well above normal temperatures expected through Wednesday

- Cooler temperatures for late this week

FORECAST UPDATE

Issued at 857 PM EDT Mon Mar 9 2026

Forecast is generally on track, only minor changes were made to increasing cloud cover overnight as well as broad brush low pops (around 20 percent) for the forecast area. As cloud cover increases, isolated showers are expected to develop after 04Z in increasing moist/waa pattern. Shallow nature of the instability beneath EML aloft noted on 00Z regional soundings will preclude any TS chances. Therefore, concur with the removal of TS in most recent Day 1 outlook.

Wind gusts were kept around 20 kts through 04Z given continued obs aided by low level mixing. However increasing nocturnal inversion and low level moistening will support diminishing trends in the next few hours.

SHORT TERM (This evening through Tuesday)

Issued at 232 PM EDT Mon Mar 9 2026

The short term will be heavily influenced by the emergence of a deep trough, currently situated over the SW CONUS. For today, a shortwave on the downwind portion of the trough will move across the Ozarks. Here is central Indiana, strong S/SSW winds ahead of this wave have pushed much warmer air into the area, with temperatures nearing or exceeding 70 across the state. There is a corridor of low stratus pushing in along a low level moisture axis ahead of the wave. This has now reaching SW Indiana, and is slowly creeping into central portions of the state. That said, the near surface column has started to destabilize this afternoon, with this stratus layer showing increasing signs of mixing as it progresses to the NE. For now, the expectation is for broken sky cover to reach the I-74 corridor, and points to the the N/W of Indianapolis by the late afternoon.

Next, this deep wave will continue its push eastward, with a split jet streak forming across the mid and upper Mississippi Valleys tonight and tomorrow. Within this split jet stream, a modest surface low is expected to develop, with confluence zones creating a instability gradient over central Illinois tomorrow afternoon. This will be the main focus for initiation during the afternoon tomorrow, as the remainder of the warm sector is likely to be too capped and cloudy for broad synoptic rising motion to be sufficient for initiation.

As far as the parameter spacing near this W/E boundary, there is a corridor of steep mid level lapse rates, but we will likely need to see some clearing and low level warming to get strong near surface lapse rates to occur. That said, low level moisture will be plenty, and once convective inhibition is overcome, there will likely be multiple cells that develop along this boundary. All severe weather threats will be possible, with hail as the main threat initially. That said, as these cells push east, right-turners will likely have sufficient enough streamwise vorticity for tornadic development. The largest area of uncertainty is on placement, with the boundary varying by 50-100 miles as of the 12z suite, but with a general southward trend. The further south this boundary is, the greater threat for severe weather for central Indiana. Given that these supercells are likely to follow a similar track, there will be a flash flood threat over portions of central Illinois and Indiana depending on where the boundary is positioned.

Overnight, greater upstream initiation post 00Z will likely grow upscale into central Indiana overnight with a marginal threat of severe wind gusts. PWATs within the moisture axis Tuesday night will also be abnormally high, with pockets of heavy rain likely. Currently the expectation is generally 1-2" across central Indiana, but there will likely be pockets of higher and lower totals depending on mesoscale influences. The greatest flooding concern Tuesday night is across southern portions of the area where FFG is will be low due to heavy rains last week, and already elevated river levels.

LONG TERM (Tuesday night through Monday)

Issued at 232 PM EDT Mon Mar 9 2026

Rain/Convection will be ongoing at the start of Wednesday. Some strong to potentially severe convection is possible. Advection will try to overcome the diurnal trend to lower instability during the morning, but there is also the possibility that a cold pool could get far enough ahead of the convection to weaken it.

Rain and some convection will continue ahead of the cold front as it moves across the area into the afternoon. If some instability is able to build during the day ahead of convection, strong to severe storms may return in the afternoon across the southeastern forecast area.

High moisture content in the atmosphere will lead to the threat of locally heavy rain and flooding Wednesday.

Temperatures will fall quickly on Wednesday behind the cold front as it passes, with readings potentially falling 20 degrees in 3 hours.

A couple of low pressure systems will impact the area during the remainder of the long term period. One will bring low PoPs to the northern forecast area on Thursday night. A stronger system will bring better rain chances around Sunday.

Below normal temperatures will return briefly on Thursday behind the first system, then readings will become above normal again into the weekend. Highs in the 60s are expected most areas by Sunday. Monday, behind the low pressure system, well below normal temperatures will return with highs only in the 30s.

AVIATION (06Z TAF Issuance)

Issued at 1235 AM EDT Tue Mar 10 2026

Impacts:

- MVFR ceilings becoming widespread during the predawn hours and lowering to IFR near daybreak - Ceilings rising back to MVFR this afternoon with gusts to 20kts developing - Scattered showers and possibly thunderstorms by mid to late evening at KLAF

Discussion:

Stratus continues to slowly expand across the region as warm advection increases. There will be breaks in the stratus for the next few hours...but expect a gradual thickening and lowering of the deck at all terminals prior to daybreak with the potential to slip to IFR. Ceilings will gradually climb back to MVFR during the afternoon with breaks developing in the stratus as low level mixing increases.

Convection will fire to the northwest of the region late today and spread east into northern Indiana this evening. There remains a possibility that storms may make it as far south as KLAF mid to late evening but overall confidence is growing in convective impacts at the terminals holding off until after 06Z Wednesday.

S/SW winds will continue through tonight...becoming gusty this afternoon and evening.

IND WATCHES/WARNINGS/ADVISORIES

None.