textproduct: Indianapolis

KEY MESSAGES

- Scattered to numerous showers and storms will be around at times later today and tonight.

- An isolated severe storm with damaging winds is possible this afternoon. Locally heavy rain remains a threat.

- Rain chances continue early this week, then dry weather should return. Temperatures will be much cooler after today.

FORECAST UPDATE

Issued at 950 AM EDT Sun Sep 20 2026

Frontal boundary remains anchored over north central Indiana this morning with convection to the north of the boundary over northeast Indiana and northwest Ohio. Further south across much of the forecast area it was a mainly sunny start to the day. 13Z temperatures were largely in the 70s.

The overall forecast captures the uncertainties and low confidence in convective potential for the rest of the day and little changes are needed. The boundary is likely to drift south into the forecast area into this afternoon but a lack of forcing and broad ridging aloft will limit and confine any potential convection to the northern tier of central Indiana counties likely in an isolated to scattered manner. While extensive cloud coverage and a shift to N/NE flow as the boundary slips south will keep temperatures in the upper 70s and lower 80s over the northern third of the forecast area... another very warm day is anticipated to the south as highs rise into the upper 80s and lower 90s. Drier air advecting off the Ozarks will lift into the Ohio Valley for the afternoon and should pull dewpoints down over southern parts of central Indiana...perhaps into the lower 60s.

The approach of a surface wave along the boundary remains the primary focus for convection late today and into tonight. Definitely potential for a few cells to produce damaging winds with modest available instability but the lack of substantial shear will keep storms at pulse intensity with locally heavy rainfall again serving as the primary threat.

Zone and grid updates out.

DISCUSSION (Today through Saturday)

Issued at 248 AM EDT Sun Sep 20 2026

Early This Morning...

Some upper energy along with the old surface front were generating some scattered showers across the northeastern half of the forecast area.

As an associated surface low across western Illinois moves east and the initial upper energy departs, the scattered showers should push east and north. Most of central Indiana should be dry by 12Z.

Today and Tonight...

Another upper wave will move east and provide forcing this afternoon. Meanwhile, the surface low will move southeast across the area.

With little or weak forcing across the area this morning, will only have some low PoPs across the far north where the front will start out.

During the afternoon, as the surface low moves through, forcing will increase. The low will drag the front south. Thus, expect scattered to numerous showers and thunderstorms to develop.

Interestingly, some drier air will get advected into the southern forecast area ahead of the surface low. This may limit convection development there until the surface front gets closer toward 00Z.

CAMs show a variety of solutions, while other guidance focuses rain north, near and behind the front. Given all the above, will go likely PoPs in the far north mid to late afternoon, tapering to slight chance in the far south. Confidence isn't great as mesoscale influences as well as the aforementioned dry air could change things.

If enough instability builds, cannot rule out an isolated severe storm with damaging winds ahead of the front. Locally heavy rain remains a threat with precipitable water values near 2 inches.

Rain chances will continue tonight as the front continues to trek south and additional upper energy moves through. Overall though forcing doesn't look great, so will keep PoPs no higher than chance category.

A strong temperature gradient will exist again today as the front moves south. Trimmed blended guidance far north given the expected location of the front and clouds/rain chances. Went near 80 far north to the lower 90s south.

Monday and Tuesday...

Upper waves on Monday followed by an approaching upper low on Tuesday will keep chances for rain around. The hot air will finally be south of the area. Highs will be in the upper 60s to near 80 on Monday with only mid 60s to lower 70s Tuesday.

Wednesday and beyond...

The far east may see an isolated shower Wednesday as the upper low exits. Otherwise, high pressure will provide dry weather into next weekend. Temperatures will start out below normal, but they will return to closer to normal next weekend.

AVIATION (18Z TAF Issuance)

Issued at 1232 PM EDT Sun Sep 20 2026

Impacts:

- Scattered convection late today through tonight and into Monday morning - Deteriorating ceilings this evening with IFR conditions developing overnight into Monday morning - Winds becoming northeast tonight and Monday

Discussion:

A frontal boundary bisects central Indiana early this afternoon with winds already having shifted to a northerly direction at all but KBMG. Mid and high level clouds were increasing over the area...with an axis of scattered cu in the vicinity of the front. The front will continue a slow southward drift through the rest of the afternoon and will pass through KBMG by early evening.

The approach of a surface wave along the boundary later today will lead to an increase in convective development extending into tonight. Could see brief restrictions within any heavier showers or storms but the primary impact to aviators will be the expansion of a broad stratus deck from north to south late this afternoon into the evening. Ceilings will eventually settle into the IFR category overnight with model soundings showing saturated conditions in the low levels. Ceilings may lift back into MVFR levels by late morning Monday as showers decrease in coverage. Northeast winds will remain around 10kts tonight and Monday with the potential for periodic gusts at KLAF.

IND WATCHES/WARNINGS/ADVISORIES

None.