Severe Thunderstorm Warning 296, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
233 PM EDT Tue Aug 11 2026

.KEY MESSAGES...

- Thunderstorms this afternoon and early evening. Some Severe.

- Flood Watch through Wednesday across much of central Indiana,
  Heat Advisory across the southwest

- Additional storms daily through the rest of the week, flooding
  will be the main threat

&&

.DISCUSSION (This evening through Tuesday)...
Issued at 233 PM EDT Tue Aug 11 2026

Surface analysis this afternoon continues to show a weak trough of
low pressure stretching from northern IL across northern Indiana
into OH. This area remains the focus for convective development.
GOES19 shows a large thunderstorm cluster over northern Indiana,
progressing to the southeast. Thunderstorms were found stretching
from a LAF to Noblesville-Anderson-Muncie areas, and was sagging
southward. Best instability across area remained southwest of the
storms where SPC CAPE showed values over 4500 J/KG. Latest ACARS
soundings show deep CAPE available. Aloft water vapor shows a short
wave within the NW flow aloft over eastern IL triggering our
convective cluster as the NW flow continue to stream from MT and WY
to Indiana.

This afternoon and tonight...

Convection across the northern parts of the forecast area is
expected to continue for the next several hours as the upper wave
continues to progress east. Thunderstorms will try to sag southward
somewhat, where the better instability will be located. Thus will
continue to keep high pops in place in this along and south of the
storms through the afternoon into the evening. Additional TSRA due
to daytime heating will be possible across southwestern central
Indiana and lower pops will still be needed there.

HRRR shows this wave exiting by early evening, and a worked over
atmosphere should allow storms to end leading to a mainly dry
evening and overnight period. Some fog will be possible near LAF due
to the high dew points remaining across the area along with the
lingering surface boundary.  Look for overnight lows in the lower
70s and the highest pops during the evening hours.

Wednesday...

The persistent NW flow aloft is expected to remain in place on
Wednesday, perhaps becoming a bit more northwesterly as yet another
short wave is expected to pass across Central Indiana within the
flow. Again the very warm and humid air mass will be in place
allowing for plenty of moisture and pwats once again are near values
1.81 inches. Again ample CAPE will be in play also. Thus high pops
will once again be used on Wednesday as this wave will pass, mainly
in the afternoon. With a good amount of daytime heating available
through the morning hours, high temperatures should again reach the
upper 80s to around 90.

Wednesday Night through Thursday Night...

Through this time period there is very little change in the overall
weather pattern. The same NW flow aloft is expected to be in place
with several embedded waves within that flow poised to pass during
this time period. The very warm, humid and unstable airmass will
also remain. All of this will add up to continued chances for
showers and thunderstorms, mainly capable of producing very heavy
rain and damaging wings through the period. Continued pops will be
used through the period.

Friday through Sunday Night....

More hot and humid weather is expected through the weekend along
with daily chances for showers and thunderstorms. Models suggest
ridging aloft over the plains will be building across Central
Indiana through the weekend. A few ridge riding waves within a ring
of fire type pattern will be capable of producing occasional showers
and storms. Further support will come from the lower levels. Here, a
frontal boundary will be lingering across Central Indiana on Friday
before pushing north as a warm front on Saturday ahead of low
pressure over the plains. The low will push east of Indiana on
Sunday, likely dragging a cold front across Central Indiana.
Forecast soundings through Sunday show plentiful moisture available
through the column. All of this will again necessitate pops through
the weekend. The warm air mass will result in high temperatures in
the upper 80s to around 90.

Monday and Tuesday...

In the wake of the front on Monday, dry air and subsidence is shown
to arrive as high pressure from the Great Lakes builds across
Central Indiana. Forecast soundings show a dry column and for the
first time in what seems like a long time show zero CAPE. Aloft,
ridging is expected to return over the Rockies resulting in NW flow
streaming across the plains into Indiana. At the moment it appears
that little to no forcing will be available, this we should able to
use a dry forecast at that time given the the expected surface high
pressure.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 121 PM EDT Tue Aug 11 2026

Impacts:

- TSRA expected at LAF and IND this afternoon
- Mainly VFR conditions, except MVFR and brief IFR in storms.

Discussion:

A Thunderstorm cluster stretching from near LAF to MIE will continue
to push east and sag southward through the next several hours. Have
included TEMPO groups for thunderstorms at LAF and IND to account
for the best window of storms passing. Storms will produce MVFR to
IFR conditions as they pass across TAF sites. The flow aloft should
keep the showers and storms remaining north of HUF and BMG, but an
isolated shower cannot be ruled out as the wave to the north passes
along with the possibility of diurnal heating related showers and
storms.

Convection is expected to diminish this afternoon and evening as the
upper wave exits and some cooling and stability reigns in the
somewhat worked over air mass. Low dewpoint depressions may lead to
overnight fog formation, particularly at LAF where rain will have
occurred.

Models suggest another upper wave arriving for Wednesday afternoon,
once again passing along the similar corridor as today. Have used a
VCTS mention for IND after 18Z as timing uncertainty remains.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Wednesday evening for INZ021-028>031-035>049-
054>057-063>065-072.

Heat Advisory until 9 PM EDT this evening for INZ060-061-067>070.

&&

AVIATION...Puma
DISCUSSION...Puma

Hazardous Weather Outlook
National Weather Service Indianapolis IN
255 PM EDT Tue Aug 11 2026

INZ021-028>031-035>049-051>057-062>065-071-072-121900-
Carroll-Warren-Tippecanoe-Clinton-Howard-Fountain-Montgomery-Boone-
Tipton-Hamilton-Madison-Delaware-Randolph-Vermillion-Parke-Putnam-
Hendricks-Marion-Hancock-Henry-Vigo-Clay-Owen-Morgan-Johnson-Shelby-
Rush-Monroe-Brown-Bartholomew-Decatur-Jackson-Jennings-
255 PM EDT Tue Aug 11 2026

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

Thunderstorms, some severe, are likely this afternoon and early
evening with the potential for damaging winds along with localized
flash flooding. Additional storms possible through the night with
flooding becoming the main threat.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Thunderstorms will be possible at times through the week, with
potential for multiple rounds of severe storms through at least
Wednesday night. Damaging winds and heavy rainfall will be the
primary threats.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to remain vigilant this week as multiple rounds
of severe storms will be possible.

&&

More information, along with other weather, hydrological and climate
information can be found at http://weather.gov/ind

INZ060-061-067>070-121900-
Sullivan-Greene-Knox-Daviess-Martin-Lawrence-
255 PM EDT Tue Aug 11 2026

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

Thunderstorms, some severe, are likely this afternoon and early
evening with the potential for damaging winds along with localized
flash flooding. Additional storms possible through the night with
flooding becoming the main threat.

Heat index values up to 105 today may cause heat related illnesses.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Thunderstorms will be possible at times through the week, with
potential for multiple rounds of severe storms through at least
Wednesday night. Damaging winds and heavy rainfall will be the
primary threats.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to monitor the severe weather threat today
and report any damage.

&&

More information, along with other weather, hydrological and climate
information can be found at http://weather.gov/ind

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