textproduct: Indianapolis

KEY MESSAGES

- Scattered showers and storms, some severe, possible this evening.

- Dry weather returns for late week into the weekend.

- Hotter and more humid air arrives Sunday into early next week.

FORECAST UPDATE

Issued at 935 AM EDT Wed Aug 26 2026

Weak lift well ahead of the main forcing of the approaching upper trough and cold front has brought some sprinkles to portions of the western forecast area this morning. Added some sprinkles where necessary this morning, but lift will continue to weaken this morning. This should end the sprinkle threat.

Clouds will diminish briefly into early afternoon, but they will increase again through the remainder of the afternoon as the cold front approaches. Heating along with moisture advection ahead of the front will lead to an increase in instability. Shear will increase as the upper trough gets closer.

Thus, expect scattered thunderstorms to develop mid to late afternoon as the cold front moves in. Shear/instability will be enough for the potential for some severe thunderstorms, with damaging winds and large hail the primary threats. Isolated tornadoes cannot be ruled out, mainly north where the better shear will exist.

Adjusted hourly temperature forecasts and tweaked high temps based on latest observational trends, but no significant changes were made.

DISCUSSION (Today through Tuesday)

Issued at 227 AM EDT Wed Aug 26 2026

Surface analysis early this morning shows high pressure in place across NY and PA. Low pressure was found over western Ontario, with a cold front that extended south into the upper Mississippi Valley. GOES19 shows high cloud across central Indiana and Illinois. Within the upper flow strong ridging remained in place over the Rockies with NW flow spilling across the northern plains into the Ohio Valley. Within this flow water vapor shows an upper low just north of MN with a trough axis across MN. This was causing a few showers and storms across central WI.

Today and this evening...

Much of the day will remain dry today as Indiana remains under the influence of the surface high pressure to the east. The cold front to the north will make steady progress toward Central Indiana today, but should not impact our area until this evening. HRRR suggests shower and storm development near 22Z, late in the day. Forecast soundings show best conditions for convection shortly after diurnal maximum, with CAPE over 1800 J/KG. Thus will expect partly cloudy skies through the day along with dry weather, but will add pops after 22Z through the evening hours as the thin line of convection pushes across the area. Confidence for rain is medium, with best chances across the eastern half of the forecast area.

Overnight through Friday...

In the wake of the front dry air, subsidence and Canadian high pressure will build across Indiana through Friday. This will result in more dry weather with mostly sunny days and mostly clear nights. Mainly north to northeasterly surface flow will be in place and this will keep our high temperatures mainly in the lower 80s, providing comfortable conditions.

Saturday through Sunday...

Models suggest that on Saturday and Sunday surface high pressure sets up off the east coast of the CONUS, allowing the development of warmer and more humid air arriving across Central Indiana on southerly winds. Mid levels suggest good subsidence still remains in place across Indiana. Strong ridging within the upper flow will be in place over MN and central Canada, resulting in lee side subsidence spilling into Indiana and the southern Great Lakes. Thus dry weather is expected on both Saturday and Sunday given this pattern. Expect above normal highs with temperatures in the upper 80s approaching 90.

Monday and Tuesday...

By Monday and Tuesday the upper pattern appears to flatten, streaming from the high plains to the Great Lakes. This results in a loss of the mid level subsidence and Pacific moisture looks to begin to stream into the region. A frontal boundary is suggested to set up NW of Indiana stretching from MI to MO, placing Indiana in the warm sector with continued warm and humid flow. Early forecast soundings suggest steep lapse rates with CAPE available. Thus given this, diurnal convection cannot be ruled out and small pops will likely be needed. Highs around 90 will be possible.

AVIATION (12Z TAF Issuance)

Issued at 607 AM EDT Wed Aug 26 2026

Impacts:

- Mainly VFR this TAF period - Scattered thunderstorms from 22Z-03Z possible.

Discussion:

Little overall change from the previous forecast discussion. Clouds over Indiana have prevented overnight fog and will limit CU development until early afternoon.

Surface high pressure over eastern OH was extending a ridge across Indiana into Illinois.

As a cold front approaches, HRRR suggests a thin line of showers and storms near the front, passing during the evening. Thus have included pop30 at this point due to low confidence in precise timing.

MVFR conditions or worse with wind gusts are possible during any thunderstorm.

A quick return to VFR conditions will arrive overnight as high pressure builds across Indiana in the wake of the front.

IND WATCHES/WARNINGS/ADVISORIES

None.