textproduct: Indianapolis

KEY MESSAGES

- A few showers are possible today, mainly this morning north of I-70

- Heavy rain and isolated severe storms are possible Sunday afternoon into early Monday as widespread rain moves in

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

FORECAST UPDATE

Issued at 1001 AM EDT Sat Jun 20 2026

Minor tweaks to the forecast to extend sprinkles for a few more hours in the N-NE. Also nudged highs up a bit in the north with sun expected most of the afternoon.

Concerns for tomorrows weather setup continues with expectation for multiple rounds of potential severe weather starting mid-late afternoon in the SW portions of the forecast area. Followed by flooding threat increasing overnight.

..HEAVY RAIN AND STRONG STORMS POSSIBLE SUNDAY AND SUNDAY NIGHT

Today and Tonight...

A weak cold front will move into central Indiana today. The front will have little upper support, and overall moisture is lacking. However, the front may squeeze out some isolated showers/scattered sprinkles across mainly the northern half of the area this morning. Will have some low PoPs for these.

By this afternoon, forcing will be weak enough that PoPs will drop below mentionable thresholds. However, some CAMs show that just enough moisture/instability will be around for a shower or two to pop up across the southern half of the area. Will have to keep an eye on it, but for now will go dry.

Tonight will be quiet with the area in between systems.

Highs today will be in the upper 70s to lower 80s, with lows tonight around 60 for much of the area.

Sunday into Monday...

An upper trough, surface low pressure, and a low level jet will create a Mesoscale Convective System (MCS) to the west which will move into central Indiana Sunday afternoon into the evening. A warm front will move into the area as the surface low moves closer during the day. The low level jet will bring in plentiful moisture to the area, with anomalously high moisture transport and precipitable water values expected.

Showers and storms will continue Sunday night as the low pressure system moves through, then rain chances diminish Monday as the system exits. Will go high PoPs all areas by early Sunday evening and will continue them Sunday night.

Shear and instability will be enough that isolated severe storms are possible with the initial MCS, especially near and south of where the warm front sets up. The severe threat may increase across the far southwest Sunday evening as thunderstorms developing along an outflow boundary from the initial storms across southern Illinois move into the area. These will have more shear to work with and could produce isolated tornadoes, mainly across the far southwestern forecast area.

With recent heavy rains, the expected high moisture content of the atmosphere, and the potential of training storms along the system's warm front, the threat for heavy rain will be high. Some guidance is showing convection exceeding 3 hour flash flood guidance, especially south. Will issue a Flood Watch for this threat. With some uncertainty in where the heaviest rain will fall, will go for all but the northeast forecast area for now, from Sunday afternoon to Monday morning.

There remains some questions with this system. There is the potential for multiple convectively induced waves of low pressure that may enhance storms/rainfall and change the location of the warm front. Even without this, there is some uncertainty on where the warm front will set up. Some guidance is also showing a split in heavier QPF, with some of it moved farther south and some going farther north than currently expected.

Depending on the timing of the MCS, highs on Sunday could reach the lower and middle 80s south and the upper 70s north. Temperatures will be cooler and in the 70s for highs Monday as the system exits.

Tuesday and beyond...

Some upper waves and surface fronts could bring rain chances at times Wednesday into Friday, but confidence isn't high enough to go more than some low PoPs. The GFS is hinting at another stronger system next weekend, but the ECMWF isn't as bullish. Northwest flow aloft will keep temperatures below normal.

AVIATION (12Z TAF Issuance)

Issued at 625 AM EDT Sat Jun 20 2026

Impacts:

- Isolated showers around this morning

Discussion:

VFR conditions are expected through the period.

A weak system will bring mainly mid clouds to the sites through at least midday. Isolated showers will be around mainly across the northern sites during the morning, so will use VCSH as needed. Cannot rule out an isolated shower this afternoon for the southern sites, but confidence is too low to include.

Winds will become more northwest during the day then diminish this evening. A few gusts over 15kt are possible this afternoon.

IND WATCHES/WARNINGS/ADVISORIES

Flood Watch from Sunday afternoon through Monday morning for INZ028>030-035>037-039-043>048-051>057-060>065-067>072.