River Flood Warning 149, NWS Indianapolis, IN

Area Forecast Discussion...UPDATED
National Weather Service Indianapolis IN
1041 AM EDT Wed Aug 12 2026

.KEY MESSAGES...

- Marginally severe storms through daybreak along with potential
  additional flooding

- Flood Watch continues through today with additional strong to
  severe storms through the day, mainly during the afternoon

- Damaging winds will be the main threat today outside of flooding

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

&&

.MESOSCALE UPDATE...
Issued at 1041 AM EDT Wed Aug 12 2026

Mesoscale forcing is maximized from near Kokomo southeastward
through Anderson, Muncie and New Castle where a subtle midlevel
thermal/moisture gradient exist. Recent radar trends have shown and
increase in convection in this area. With mean flow parallel to
this, deep warm cloud layer, and anomalous moisture, training heavy
rain-producing convective elements will likely continue in the near
term resulting in significant flash flooding potential in this
corridor.

&&

.DISCUSSION (Today through Tuesday)...
Issued at 133 AM EDT Wed Aug 12 2026

Overview.

Active weather continues into today with additional rounds of showers
and thunderstorms. A few storms could produce localized heavy rain
and strong gusty winds this afternoon and evening with best chances
across southwest Indiana. A front associated with the system will
gradually move south into early Thursday with additional marginally
severe storms through Friday. Rain chances generally look lower for
the weekend with the jet stream further north into the Great Lakes.

Rest of Tonight.

The main focus through the remainder of the overnight hours will
be additional thunderstorm development across eastern Indiana with
the LLJ ramping up. Storm coverage has been gradually increasing
over the last 2 hours with heavy rain being the main threat along
with occasional pulses leading to small hail. General expectations
are for these storms to grow upscale and move to the southeast
with additional flooding from Madison County south to Decatur
county. With the storms not backbuilding as much as they were
initially, flash flooding should remain isolated with broader
areal flooding being the main threat.

Wednesday Through Thursday.

Indiana remains locked into northwesterly flow with broad ridging
across the Central Plains and broad troughing across the Great
Lakes. Shortwaves within the upper level flow will continue to bring
periods of showers and storms  with upper-level forcing along the
exit region of a 50-60 kt mid-level jet streak aloft. A weak surface
front currently across northern Indiana is expected to slowly move
south through the day but generally will only have minimal impacts
on storm coverage timing as much of the forcing is being driven by
the jet level forcing aloft.

WAA and boundary layer heating will yield MLCAPE values ranging
between 2500-3500 J/kg again today, supported by steep lapse rates
exceeding 7.5 C/km above the boundary layer. While 0-6 km bulk shear
vector magnitudes are modest at 25-35 kt, orientation roughly 45
degrees to the initiating boundary favors mixed mode convective
structures, including multicellular clusters and bowing segments.
HREF 2-5 km UH probability sweeps show maximum signal concentrated
across central and southern Indiana between 21Z and 03Z with storms
moving in from the west. Elevated DCAPE values above 1000 J/kg
suggest damaging wind gusts will be the primary severe hazard, with
steep mid-level lapse rates occasionally supporting isolated severe
hail. PWATs nearing 1.8 to 2.0 inches, well above the 90th
percentile, will support efficient warm-rain processes and localized
torrential rainfall. Ahead of the stronger storms, initiation is
likely across northern Indiana during the early morning hours today,
but CAMs continue to struggle with properly diagnosing the current
boundaries and impacts from the front, so confidence is lower on any
impacts through the morning hours.

Additional flooding looks likely, especially in areas that saw
heavy rain during the overnight hours. LPMMs show pockets of 2-3
inches beyond what already fell, but confidence is very low in
where this may occur with broader model spread on the location of
the axis of heaviest rain. Thus, will keep the Flood Watch through
04Z and reevaluate later today.

Convection will clear the southern CWA border late tonight as the
surface cold front gradually drifts into closer to the Ohio River.
Forecast confidence is fairly low into Thursday with more
significant model divergence on the broader synoptic pattern and how
the residual front may impact conditions. North of the front,
temperatures will be much cooler with highs in the upper 70s to near
80 with minimal instability, while areas to the south of the front
are likely to end up near 90. The severe threat generally should be
on the warmer side with any convection to the north remaining
elevated.

Friday Through Tuesday.

The broad synoptic regime during the extended period will feature a
transition from post-frontal surface high pressure to mid-level
ridge amplification across the Central Mississippi and Ohio Valleys.
The 00Z GEFS and EPS are in have decent agreement through 00Z
Monday, with the ridge over the Plains strengthening and pushing the
jet stream further north into the Great Lakes. Daytime highs will
climb from the lower 80s on Friday to the upper 80s and low 90s by
Sunday as return southerly flow returns. Rain chances generally
should remain limited to just the northern counties, but even that
looks low.

By Monday into Tuesday, ensemble guidance indicates a northern
stream trough traversing the Canadian Prairies into the Great Lakes
region, acting to flatten the mid-level ridge and push a surface
cold front toward the lower Great Lakes. Guidance exhibits typical
timing disparities regarding frontal passage dynamics, with the
ECMWF and EPS ensemble mean slightly slower than the GFS and GEFS
composite. Low-level moisture return along a re-establishing 30 kt
LLJ will bring PWATs back toward 1.5-1.7 inches. Chance POPs have
been maintained for Monday afternoon through Tuesday to account for
scattered frontal convection driven by weak height falls and low-
level convergence.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 706 AM EDT Wed Aug 12 2026

Impacts:

- Isolated showers or a stray storm cannot be ruled out near IND
  this morning along with MVFR ceilings

- Additional convection later today, confidence highest towards mid
  afternoon

- Fog development expected tonight, especially near LAF/HUF

Discussion:

Brief fog development will be possible through 13Z near LAF/HUF.
Isolated showers or a stray storm cannot be ruled out near IND
this morning along with MVFR ceilings. Additional storms are
likely later today followed up by more widespread strong to severe
storms in the afternoon and evening, mainly towards BMG/IND/HUF.
Brief MVFR or worse conditions are possible with any
thunderstorms. Outside of convection, winds will generally be
south or southwesterly at 5-10kts through the TAF period.

Fog development is expected by late tonight, especially near HUF/LAF.

The LAF ASOS is currently out of service, so no AMDs are scheduled
beyond typical TAF issuances due to low confidence on present
weather.

&&

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

&&

MESOSCALE...BRB
AVIATION...Melo
DISCUSSION...White

Hazardous Weather Outlook
National Weather Service Indianapolis IN
237 AM EDT Wed Aug 12 2026

INZ021-028>031-035>049-051>057-060>065-067>072-130645-
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-Sullivan-Greene-Monroe-Brown-Bartholomew-Decatur-Knox-Daviess-
Martin-Lawrence-Jackson-Jennings-
237 AM EDT Wed Aug 12 2026

This hazardous weather outlook is for central Indiana.

.DAY ONE...Today and Tonight.

Flooding and flash flooding will continue across eastern Indiana
through daybreak. Afterwards, showers and storms are expected to
return late morning into the afternoon with the potential for
additional flooding and damaging winds.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

Thunderstorms will be possible at times through the week, with
potential for multiple rounds of severe storms through at least
Thursday. 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

Preliminary Local Storm Report
National Weather Service Indianapolis IN
449 AM EDT Wed Aug 12 2026

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

0445 AM     Flash Flood      4 SSE Fountaintown      39.64N 85.77W
08/12/2026                   Shelby             IN   Public

            Water was flowing over State Road 9 north of
            Shelbyville.

0430 AM     Flash Flood      Middletown              40.06N 85.54W
08/12/2026                   Henry              IN   Public

            At least one home flooded.

&&

Preliminary Local Storm Report
National Weather Service Indianapolis IN
455 AM EDT Wed Aug 12 2026

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

0454 AM     Flash Flood      Greensburg              39.34N 85.49W
08/12/2026                   Decatur            IN   911 Call Center

            Several flooded roads with at least one
            having water flowing over it. No specific
            location in the county noted.

&&

AW

Preliminary Local Storm Report
National Weather Service Indianapolis IN
615 AM EDT Wed Aug 12 2026

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

0615 AM     Flash Flood      5 SSE Farmland          40.12N 85.09W
08/12/2026                   Randolph           IN   911 Call Center

            Water flowing over a road in the western
            portion of the county.

&&

AW