River Flood Warning 166, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
357 PM EDT Thu Aug 13 2026

.KEY MESSAGES...

- Heavy rain and localized flash flooding remain the primary concern
  today, especially across north central Indiana into the overnight.

- Continued Rain tonight and on Friday will worsen an already
  very significant flooding event.

- A few severe thunderstorms are possible this afternoon with damaging
  wind is gusts as a storm complex moves in from the west

- Additional storm chances continue Friday into Saturday as a warm
  front lifts north followed by a cold front over the weekend

- Warmer and more humid conditions return Saturday before drier and
  cooler weather settles in Sunday through early next week

&&

.MESOSCALE UPDATE...
Issued at 357 PM EDT Thu Aug 13 2026

Cluster of strong to severe storms over the IL/IN border will move
SE 30-40 mph, tracking along and down into a strong instability
gradient (SBCAPE 3000-4000 J/KG) extending along and south of I-74.
Recent ACARS soundings from KIND show around 1200 J/KG of DCAPE.
Although the cluster remains small in size, upscale growth owing to
cell mergers and enhancement of downdrafts from aforementioned DCAPE
will support an increasing damaging wind threat. Recent storm
reports and obs upstream suggest wind gusts to 70 mph will be
possible. This activity should reach the Indy metro area between 5
and 6 PM likely leading to significant impacts to the evening rush.
In addition, very heavy rainfall rates from 1-2 inch/hr will lead to
minor flooding, especially in poor drainage areas and urban areas.

An isolated/brief tornado is possible along the northern/eastern
edge of the cluster where enhanced low level vertical shear will
combine with antecedent modest 0-3 KM CAPE of 100-150 J/KG, and
background vorticity along weak outflow boundary.

&&

.DISCUSSION (This evening through Thursday)...
Issued at 227 PM EDT Thu Aug 13 2026

Surface analysis this afternoon shows a trough axis across
central IL to the northern parts of Central Indiana. The convective
complex has advanced to Central IL. Radar shows a few scattered
thunderstorms ahead of this line pushing across eastern IL. Dew
points have surged to the 70s, but temperatures have been a bit slow
to rise due to cloud cover.

Tonight...

Uncertainty exist with he progression of the thunderstorm cluster
over IL. This system appears to be moving in to a less favorable
environment, due to morning clouds, but with the afternoon heating,
the environment is becoming more favorable for continued progression
to the ESE.

The continued NW flow aloft and another short wave are expect
overnight. This will generate showers and thunderstorm once again
overnight. Models show favorable isentropic lift setting up ahead of
the short wave overnight particularly along and north of LAF to
Rushville Axis. Given our very high dew points showers and storms
will be efficient rain producers and 1-2 inches of rain with
isolated higher amounts cannot be ruled out. Forecast soundings show
a saturated column with very high pwats over 2.2 inches overnight.
Additional rainfall over already flooded area may worsen the
situation. Thus will be using high pops tonight, focusing the best
timing from mid evening through 08Z.

Friday and Friday Night...

Models continue to suggest ridging riding forcing dynamics
continuing to pass across Central Indiana on Friday, with the
favorable air mass still in place along with the trough axis slowly
moving south across Indiana. Forecast soundings on Friday remain
saturated with very pwats still above 2 inches as lift and
instability remain in place. Thus will continue high pops through
the day again on Friday and Friday night, with best chances to
remain along and near and I-74 corridor.

Saturday and Saturday Night...

Forecast soundings are shown to dry out on Saturday and Saturday
night as convective temperatures become unreachable. However a very
warm and humid air mass will remain in place which may result in
need for a heat advisory as mid 90s will be possible. Models hint
that the best forcing path will push to the north and more limited
embedded waves look to pass. Thus should there be any diurnal
convection, best chances would be across the already soaked northern
parts of the forecast area.

Sunday and Sunday Night...

Rain chances look to persist on Sunday as a cold front will push
across Central Indiana though the afternoon and into the evening.
Upper levels suggest a continued WNW flow with a weak short wave
passing through the afternoon to provide forcing. Warm and humid air
will be in place ahead of this system. Thus plenty of factors in
play to support pops. Cold front is suggested to sag southward to
the Ohio River by late Sunday Night and precip should end near that
time.

Monday through Thursday...

Models suggest continue WNW flow in place aloft during this time,
but little in the way of forcing dynamics appear to be in play.
Meanwhile during this time, cooler high pressure in the wake of
Sunday's cold front will be pushing across Indiana and through the
region. This will lead to lower dewpoints and cooler highs. Forecast
soundings show a dry column through Wednesday morning as these
features pass.

On Wednesday afternoon and into Thursday the surface high will be
departing to the southeast. This will allow another surface boundary
over the Great Lakes to sag southward across Indiana at this time.
By this time, southerly return flow will have allowed warmer and
more humid air to arrive across Central Indiana. Furthermore, the
flow aloft looks to become more NW as ridging over the western US
becomes more amplified. Although the signal for embedded waves
within this flow is unclear at this time, given the pattern,
embedded waves providing forcing appears plausible. Thus pops and
warmer temperatures will be used.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 631 AM EDT Thu Aug 13 2026

Impacts:

- MVFR/IFR conditions possible in fog and stratus through daybreak

- More widespread TSRA possible Thursday afternoon, potential for
  heavy rain during the overnight towards LAF

Discussion:

Some partial clearing of clouds, lessening wind, and wet ground from
recent rains will lead to fog/stratus development through daybreak.
Expect most of it to occur from 09Z to 12Z. IFR and worse is likely
at KLAF, with MVFR and potentially worse elsewhere. Fog will mix out
by 14Z.

Rain coverage through daybreak will likely remain limited to just
HUF with lower chances at IND and BMG. Rain coverage then should be
fairly low through the day before a complex of storms moves in from
the west during the afternoon. Training storms then are likely
tonight towards LAF with the potential for an extended period of
MVFR to IFR vsbys.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 8 PM EDT this evening for INZ021-028>031-
035>049-051>057-060>065-069>072.

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

&&

MESOSCALE...Crosbie
AVIATION...White
DISCUSSION...Puma

Hazardous Weather Outlook
National Weather Service Indianapolis IN
317 PM EDT Thu Aug 13 2026

INZ021-028>031-035>049-051>057-060>065-067>072-141930-
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-
317 PM EDT Thu Aug 13 2026

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

Flooding will continue across mainly eastern portions of central
Indiana. Some portions of the Upper White River and Big Blue River
may reach major flood stage.

Strong to severe storms will be possible this afternoon and evening
with damaging winds as the main threat. Flash flooding then looks
likely through the overnight, mainly across the I-74 corridor.

Heavy Rain is possible along and north of the I-74 corridor tonight.
This may result in flooding and flash flooding.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

Heavy Rain is possible along and north of the I-74 corridor on Friday.
This may result in flooding and flash flooding.

Thunderstorms will be possible at times through the weekend along
with continued river flooding.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to remain vigilant this week as multiple rounds
of severe storms will be possible. Report incidents of Flooding. Do
not enter flooded areas.

&&

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

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