Severe Thunderstorm Warning 281, NWS Indianapolis, IN

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

.KEY MESSAGES...

- Severe storms likely today, best chances during the afternoon and
  evening

- Flood Watch today 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

&&

.FORECAST UPDATE...
Issued at 857 AM EDT Tue Aug 11 2026

GOES19 this morning shows a convective complex over NE
Indiana progressing SE within the upper flow. Radar trends show this
system clipping our NE forecast area before exiting within the next
90 minutes. Another convective cluster was found over NE IA,
drifting SE within the flow aloft. The current convective cluster
was laying out an outflow boundary across Central Indiana that was
stretching from southern Madison county, across Fishers and Carmel
to Lebanon and Lafayette. This area could be the focus for
additional development or storm propagation later today.

A weak surface trough was found stretching IA across Nrn IL to
northern Indiana. This was the area where current convection
continues. Water vapor shows NW flow in place from MT and WY,
flowing across the northern plains to Illinois and Indiana. embedded
forcing remains within this flow helping to generate our rounds of
thunderstorms. ACARS soundings at IND shows deep CAPE available with
a lower level inversion present. Dew points remain quite high, in
the low to mid 70s.  Thus plenty of moisture and potential
instability remain in place across Central Indiana. HRRR quickly
moves the ongoing system SE to OH this morning, but redevelopment
is shown to appear over over northern Indiana by mid afternoon.
Potential for this to be further south, along the previously defined
boundary is present. Thus will drop pops low late this morning, but
return to higher pops in the northern parts of the forecast area
given the expected daytime heating, forcing and moisture in our
area. Cloud cover across the area may limit highs acrs the NE parts
of the forecast area. Otherwise, the highs in the low 90s, within
the heat advisory area, appear on the mark.

&&

.DISCUSSION (Today through Monday)...
Issued at 139 AM EDT Tue Aug 11 2026

Overview.

Severe weather is likely today with a complex of storms moving in
from the northwest. Repeated rounds of thunderstorms are expected to
continue through Wednesday night with lower chances through the
remainder of the week. Damaging winds and flooding will be the main
threats today and tomorrow. Outside of storms, heat will be a
concern today with heat index values up to 105 in southwest Indiana.

Today Through Tonight.

Central Indiana remains positioned along the northeastern periphery
of a strong subtropical ridge centered over the southern Plains,
maintaining an active northwest flow regime aloft. Low-level WAA and
moisture transport continue to stream across the region, yielding
surface dewpoints in the mid-70s and PWAT values approaching 2.0 to
2.2 inches. Strong diurnal heating will destabilize the boundary
layer today, yielding SBCAPE values exceeding 3500-4500 J/kg by
afternoon. High temperatures rising into the upper 80s to low 90s
combined with elevated humidity will create heat index values near
105 degrees, particularly across southern and central counties. A
Heat Advisory is in effect for southwestern Indiana from 12PM to
9PM.

Convective initiation and timing remain tied to subtle shortwaves
riding the ridge edge and residual boundaries from previous
storms.

00Z model guidance actually is in fairly good agreement on the
broader timing for convection through daybreak and into today, but
differ on the exact details. Broadly, there is good agreement in
initiation continuing over the next couple of hours over northern
Illinois/northern Indiana, likely along the remnant outflow boundary
from the earlier convection. Some models have this quickly growing
upscale into an MCS that dives south, but with the fairly stable
near surface, expect these storms to remain elevated and generally
sub-severe. The second round would then initiate across eastern Iowa
and northern Illinois towards mid-morning with quick upscale growth
into an MCS and an arrival near the I-74 corridor towards the late
afternoon to early evening. By the time storms arrive SB CAPE values
will be in excess of 3500 J/kg across central Indiana with
sufficient shear to maintain an organized MCS with the potential for
widespread damaging winds. If storms through daybreak do end up
growing upscale, this could delay the second round by a few hours,
but with the very humid airmass, it looks unlikely that any morning
convection would significantly lower any risk later in the day.

Regardless of timing, heavy rainfall and flash flooding will be
another significant concern. High freezing levels above 14,000
feet and deep warm-rain processes combined with the potential for
training convective cores along the western periphery of the
complex raise flash flood potential. HREF probability matched mean
guidance indicates localized rainfall totals of 2 to 4 inches
where storm training occurs. With that in mind, a Flood Watch is
in effect from 12PM through 10PM with the potential need for an
extension or additional watch for Wednesday.

Wednesday Through Monday.

The active synoptic configuration persists into Wednesday as central
Indiana stays situated in the baroclinic gradient on the eastern
flank of the southern ridge. Global guidance, including the GFS and
ECMWF, depicts a prominent mid-level trough digging from the Upper
Midwest into the Great Lakes on Wednesday. This wave will help to
push the aforementioned surface cold front southward through the CWA
late Wednesday through early Thursday morning. Deep-layer moisture
remains unseasonably high across the southern half of the forecast
area with PWATs lingering near 2.0 inches ahead of the boundary. The
combination of frontal forcing, upper-level jet divergence, and
moderate instability will generate another round of showers and
thunderstorms Wednesday afternoon and night. The GEFS and EPS
ensemble means show strong agreement on severe weather and heavy
rainfall potential continuing along and south of I-70 until frontal
passage occurs early Thursday.

By Thursday night into Friday, model guidance agrees on the southward
progression of the surface cold front into the Ohio Valley, bringing
at least some minor relief from the hot and humid conditions. High
temperatures Thursday and Friday will moderate into the low to mid-
80s with dewpoints dropping into the upper 60s to low 70s for all
but the southern portions of the state. Low-end chance PoPs are
maintained across southern counties beginning Friday morning to
account for residual elevated moisture and minor shortwave energy
overriding the frontal zone, but the overall threat for severe
weather and flash flooding will wane significantly.

For the weekend, the overall synoptic evolution diverges slightly
between deterministic operational runs. The ECMWF maintains quasi-
zonal flow aloft with surface high pressure shifting toward the East
Coast, keeping central Indiana mostly dry with temperatures near
seasonal normals. The GFS suggests a faster return of low-level warm
air advection and ridge building northward into the Ohio Valley by
Sunday, introducing isolated diurnal thunderstorm chances. EPS and
GEFS ensemble cluster analyses favor a drier consensus for Saturday
before gradually increasing PoPs across western counties late Sunday
into Sunday night.

&&

.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 until midnight EDT tonight for INZ021-028>031-
035>049-054>057-063>065-072.

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

&&

UPDATE...Puma
AVIATION...Puma
DISCUSSION...White

Hazardous Weather Outlook
National Weather Service Indianapolis IN
234 AM EDT Tue Aug 11 2026

INZ021-028>031-035>049-051>057-062>065-071-072-120645-
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-
234 AM EDT Tue Aug 11 2026

This hazardous weather outlook is for central Indiana.

.DAY ONE...Today and Tonight.

Severe storms likely today with the potential for a storm complex
with widespread 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>070-120645-
Sullivan-Greene-Knox-Daviess-Martin-Lawrence-
234 AM EDT Tue Aug 11 2026

This hazardous weather outlook is for central Indiana.

.DAY ONE...Today and Tonight.

Severe storms likely today with the potential for a storm complex
with widespread 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

Preliminary Local Storm Report
National Weather Service Indianapolis IN
1240 PM EDT Tue Aug 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1232 PM     Hail             3 S Wawpecong           40.53N 86.06W
08/11/2026  M0.50 Inch       Howard             IN   Public

            Report from mPING: Half-inch (0.50 in.).

&&

BH

Preliminary Local Storm Report
National Weather Service Indianapolis IN
150 PM EDT Tue Aug 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0135 PM     Tstm Wnd Dmg     1 W Frankfort           40.29N 86.53W
08/11/2026                   Clinton            IN   Trained Spotter

            Numerous branches...rotted trees...and
            utility lines down across Clinton County.
            Estimated wind gusts near 65 mph.

&&

BH

Preliminary Local Storm Report
National Weather Service Indianapolis IN
153 PM EDT Tue Aug 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0133 PM     Tstm Wnd Gst     2 SW Purdue University  40.41N 86.94W
08/11/2026  M63 MPH          Tippecanoe         IN   ASOS

&&

BH

Preliminary Local Storm Report
National Weather Service Indianapolis IN
154 PM EDT Tue Aug 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0139 PM     Hail             1 S Frankfort           40.27N 86.51W
08/11/2026  E0.25 Inch       Clinton            IN   Law Enforcement

&&

BH

Preliminary Local Storm Report
National Weather Service Indianapolis IN
156 PM EDT Tue Aug 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0150 PM     Tstm Wnd Gst     1 S Lebanon             40.03N 86.47W
08/11/2026  E60 MPH          Boone              IN   Amateur Radio

            Pea size hail.

&&

BH

Preliminary Local Storm Report
National Weather Service Indianapolis IN
207 PM EDT Tue Aug 11 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0204 PM     Hail             3 SE Noblesville        40.03N 86.00W
08/11/2026  E0.25 Inch       Hamilton           IN   Emergency Mngr

&&

BH