textproduct: Indianapolis

KEY MESSAGES

- Flood Watch through Thursday evening

- Scattered showers and storms overnight but better chances for storms on Thursday afternoon and evening.

- Severe storms possible again Thursday

- Storm chances continue through the rest of the week, severe weather threat looks lower for Friday

FORECAST UPDATE

Issued at 936 PM EDT Wed Aug 12 2026

Some lift has generated scattered showers across the southern half of central Indiana this evening.

These showers will continue to move southeast as the lift moves through the steering flow. Instability is limited thanks to today's earlier convection, but there may be enough for a thunderstorm. Severe convection isn't expected given the limited instability. Brief heavy rain is possible, but fortunately these will be avoiding most of the areas that have seen significant flooding.

More scattered convection may develop overnight, especially south, as warm advection aloft increases. Will have some chance PoPs there. Although overall instability will increase some thanks to the warm advection, feel that odds of severe storms are very low. Heavy rain will remain a threat though with any storm.

Rain cooled air will prevail during the night with the warm advection occurring aloft. Have lowered hourly temperatures as well as forecast low temperatures based on latest trends.

Some partial clearing along with light winds and plentiful low level moisture will lead to at least patchy fog overnight for much of the area. Locally dense fog is possible.

DISCUSSION (This evening through Wednesday)

Issued at 249 PM EDT Wed Aug 12 2026

Surface Analysis this afternoon shows a broad surface trough stretching from central IL to across Central Indiana. Convection continued along this trough spreading showers and thunderstorms across much of Central Indiana. Water vapor shows a steady NW flow aloft in place, with an wave over IL, generating convection downstream. Dewpoints remained high, in the 60s as much of the area was under the influence of rain cooled air, however across southwest Central Indiana, dew points were in the 70s, providing very humid conditions along with the best instability.

This afternoon through the overnight...

The Thunderstorm complex over Central Indiana will continue to propagate SE across Central Indiana through the late afternoon hours. Heavy rains may result in additional flooding and severe storms cannot be ruled out. Near 00Z the HRRR progresses this system further SE, exiting Central Indiana as the forcing with upper wave exits. Clouds will remain across the area through the evening with rain cooled air in place.

Overnight as the LLJ resumes, more storm development will be possible, but at this time HRRR is developing storms along the boundary which at that time should be located across southern Central Indiana due to the southward push from today's convection. Thus will focus best pops overnight in those locations. Fog will also be possible overnight due to high dew points, light winds and plenty of lingering lower level moisture.

Thursday and Thursday Night...

More rain chances will be expected on Thursday afternoon and into Thursday night. The persistent NW flow aloft is once again expected to continue across central Indiana. An upper level wave is expected to pass across central Indiana providing forcing through the afternoon hours. The location of the surface trough will be key in best initiation and propagation area. For now, this is suggested to be across southern Central Indiana, but changes can occur overnight. Forecast soundings show shallower CAPE at that time with values only around 1000-1500 J/kg across Central Indiana, but much higher values south of boundary in the warmer and humid air mass. Thus will again use high pops on Thursday afternoon for more showers and storm development given the familiar, favorable set-up in place. Again, best chances for now will be across southern Central Indiana which is the expected location of the surface trough. Flash Flood Watch will be extended.

Friday and Friday Night...

Strong ridging within the upper flow is expected to push east toward Indiana on Friday. This will allow surface warm front to surge across Central Indiana as flow becomes southwesterly. Forecast soundings again on Friday show a nearly saturated column at times, with pwats once again over 2 inches. Again shallow CAPE appears available. Thus again likely pops will be needed from the afternoon and into the evening as the warm front surges northeast across the area and acts as a focus for convection.

Saturday through Sunday Night...

Rain chances will persist on Saturday and Sunday as a warm frontal boundary is suggested to be lingering across Central Indiana. Working against this will be the pattern aloft where upper level ridging will be building across Indiana from the west. This will result in some subsidence within the mid and upper levels. However, diurnal convection cannot be ruled out due to the frontal boundary that will be present across the area on Saturday as a warm front and on Sunday as a cold front crossing Indiana. SW flow ahead of the cold front will result in hot weather on Saturday and again on Sunday with highs in the 90s.

Monday through Wednesday...

Better chances for dry weather and temperatures closer to normal will be expected during this time. Northwest flow is expected to resume across the area on Monday due to upper ridging in place over the Rockies. Little in the way of forcing looks to pass during this time. Meanwhile at the lower levels, stronger Canadian high pressure will be building behind Sunday's cold front on Monday and through the first part of the next work week. This should result in partly cloudy skies and highs in the 80s. Temps will moderate by Wednesday as the surface high drifts farther east and southerly return flow begins.

AVIATION (00Z TAF Issuance)

Issued at 742 PM EDT Wed Aug 12 2026

Impacts:

- MVFR/IFR conditions possible in fog and stratus overnight

- More widespread TSRA possible Thursday afternoon

Discussion:

Some partial clearing of clouds, lessening wind, and wet ground from recent rains will lead to fog/stratus development tonight. Expect most of it to occur 06-12Z. IFR and worse is likely at KLAF, with MVFR and potentially worse elsewhere. Fog will mix out by 14Z.

While an isolated shower or storm cannot be ruled out overnight at mainly the southern sites, better chances for convection will arrive Thursday afternoon. Uncertainty remains high on details, so will do a broad VCTS for Thursday afternoon.

IND WATCHES/WARNINGS/ADVISORIES

Flood Watch through Thursday evening for INZ021-028>031-035>049- 051>057-060>065-069>072.