Flash Flood Warning 3, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
1003 PM EDT Mon Apr 27 2026

.KEY MESSAGES...

- Multiple rounds of thunderstorms expected today, severe weather is
  possible this afternoon into tonight.

- Isolated Showers and thunderstorms possible on Tuesday, mainly
  across southern Indiana.

- Cooler temperatures expected Wednesday through Sunday.

- Flash flood threat across southern Indiana with multiple rounds
  of heavy rainfall.

&&

.MESOSCALE UPDATE...
Issued at 1002 PM EDT Mon Apr 27 2026

Surface analysis shows the outflow boundary remains over far
southern portions of Indiana. A wake low/meso-high earlier this
evening has lead to fairly strong E-SE low level flow in near
surface layer. This combined with increasing 1-2 KM LLJ, has aided
in strong low level shear recent KIND VWP showing between 350-450
M2/S2 of 0-1 KM SRH.

Recent KIND ACARS sounding confirms with RAP mesoanalysis that
around 200-300 J/KG of MLCINH exists over most of central Indiana
which is limiting the threat for QLCS tornadoes except in brief
instances where meso-vortices can be maintained either with cell
mergers or within bowing segments of the line. Steep mid level lapse
rates from 7-7.5 C/KM along with extremely strong effective bulk
shear of 60-70 kts will continue the threat for severe hail.

Damaging wind gusts from 60-70 mph will continue to be the primary
threat especially in bowing segments that are perpendicular to the
deep shear vector. The damaging wind threat will reach the Indy
metro by 11 PM. Further south, rainfall accumulations from 3-5
inches have lead to flash flooding potential. Increasing heavy
rainfall with the convective line will support additional threat for
heavy rainfall and localized flash flooding south of I-70 through
the early AM period.

&&

.DISCUSSION (This evening through Monday)...
Issued at 158 PM EDT Mon Apr 27 2026

Surface analysis late early this morning shows deepening low
pressure over IA and MN, with a cold front extending south across IA
to Central MO and NE OK. An area of strong convection had developed
within the warm sector, over IL and was pushing east toward Indiana.
Cloud tops continue to show steady state or slightly cooling tops.
However the strongest echos were now pushing into a more stable area
of air as showers have been falling in the Wabash Valley. Expected
progression of the storms will be to the east, but conditions across
Indiana were less favorable for convection. A better area for storms
was found across southern Central Indiana with more access to
instability there. Aloft, water vapor shows a moderate short wave
over the Dakotas with a southwest flow of air ahead of this wave
spreading across Illinois and Indiana amid weak diffluence aloft.

Tonight...

SEVERE WEATHER THREAT REMAINS TONIGHT.

Models show the upper wave progressing across the region, continuing
to spread forcing dynamics across Indiana through the evening,
Caveats have come into play. Namely, the cloud cover across Central
Indiana from convection upstream have not allowed for peak heating.
CAPE across the area remains limited this afternoon and the
convection is expected to spread across Indiana in a decaying state
late this afternoon. This will further diminish our severe weather
threat. Later this evening, HRRR suggests more development over
southern Illinois, pushing east into SW central Indiana. Confidence
is higher for these storms to be strong to severe, perhaps impacting
Vincennes, Sullivan, Linton, Washington and Shoals. Damaging
straight line winds will continue to be the main threat, again an
isolated QLCS tornado.

After a rainy evening, upper forcing is shown to end toward 05Z.
Forecast soundings show drying and subsidence as the upper trough
axis exits to the northeast. Lower level cloud cover should remain
through the night, as lower level moisture remains trapped
underneath an inversion.

Thus overall, high confidence for rain and storms this evening, with
best chances across the southern and southwest parts of the forecast
area. This will be followed by cloudy skies tonight. Little overall
change in the air mass will result in lows only in the upper 50s as
dew points are expected to remain in the 50s.

Tuesday...

Dry weather is expected on Tuesday as the upper flow is
nearly zonal, with little in the way of forcing dynamics passing
across Indiana. Forecast soundings continue to show a dry column
with subsidence ongoing with the departure of the previous wave. At
the surface, high pressure over the northern plains will continue to
spill southeast toward Indiana. Thus after morning clouds, some
afternoon sunshine should become available. Highs will reach the
upper 60s to around 70.

Tuesday Night and Wednesday...

Showers and Thunderstorms will be expected during this time,
particularly on late Tuesday Night into Wednesday. Models show
another subtle short wave within the broader cyclonic flow aloft
pushing across our region on late Tuesday night into Wednesday. A
weak area of surface low pressure is expected to ride this wave,
pushing across KY, and placing Indiana on the NW side of the low.
Forecast soundings show the arrival of deep saturation late Tuesday
Night into Wednesday with pwats as high as 1.7 inches. Thus
confidence is high for another round of rain showers on at this
time. Rain showers will exit by Wednesday afternoon as the upper
forcing and surface low departs. northerly surface winds in the wake
of the this system will allow for cooler temperatures on Wednesday,
with highs only in the lower to middle 60s.

Thursday Through Monday...

Indiana/s weather during this period will be controlled mainly by a
strong area of upper level low pressure over Ontario and Quebec.
This feature is suggested to rotate waves within this flow across
Indiana, mainly on Friday and again on Monday. The upper flow during
this time will be mainly a northwest fetch spilling toward Indiana
from Central Canada, providing mainly dry and cool air, due to the
low to the northwest. It is only when the weak waves pass that
enough forcing will be present to result in shower or storm chances.

Through this period within the lower levels surface high pressure
looks to be anchored over the plains states, keeping mainly westerly
or northwesterly flow in place across Indiana. Models suggest a
poorly organized cold front to pass on Friday, but this system lacks
access to deeper gulf moisture. A weak area of low pressure is
suggested to pass across Indiana on Monday, again associated with
the upper level feature.

Thus will try to contain pop chances to just Friday and Monday, with
mainly dry and cool weather expected on Thursday, Saturday and
Sunday.

As no intrusions of arctic or tropical air are expected, look for
temperatures to be near or below typical seasonal lows.

&&

.AVIATION (00Z TAF Issuance)...
Issued at 813 PM EDT Mon Apr 27 2026

Impacts:

- S-SE wind gusts 20 to 35 kt with higher gusts in TSRA
- Scattered storms across area through the evening
- Next line of storms to move through TAF sites around 02-05z
- MVFR ceilings overnight into early Tuesday

Discussion:

Non-thunderstorm stronger wind gusts will persist early in the
period with gusts around 35kt possible. Scattered convection will be
ahead of the main line of convection, and the main line is expected
to move through in the 02Z-05Z time frame. Gusts over 45kt, hail,
and IFR/worse conditions are possible in the convection.

Overnight, MVFR ceilings will develop and persist into Tuesday
morning. Winds will become west into Tuesday.

&&

.HYDROLOGY...
Issued at 324 PM EDT Mon Apr 27 2026

Precipitable water values are forecast to be increasing to
over 1.5 inches until around 6z or thereafter. While a morning
sounding launched from IU Bloomington showed a distinct and deep dry
layer in the mid levels, advection of deep moisture is occurring and
should make for more efficient rain processes. The current
convective line has taken on a more southwest to northeast
orientation, and the back edge of this is becoming more WSW to ENE.
Several different ensemble members are showing the potential for 3
hour rainfall amounts approaching/exceeding 3 inches along the I-70
corridor and this has resulted in a highlight from the urban rain
rate dashboard for Indianapolis. HREF has LPMM bullseyes of 5 to 7
inches by Tuesday morning embedded in a larger area 3 to 5 inches
over an area along I-70 and southward over much of western Indiana
eastward to about I-65. WOFS runs are highlighting similar high
rainfall amounts with high probabilities of over 3 inches in 3
hours, again along I-70. Training of cells over the same area could
increase with time as a boundary stalls out and low level jet ramps
up perpendicular to the boundary similar to surface flow, but the
mid level flow is more oriented along the boundary. Last couple of
HRRR runs have bounced back and forth with the precip amounts in
excess of 3-4+ inches, with the 17z run trending higher again and
further north, but majority of factors including current satellite
and radar trends are favoring the areas along I-70 and southward.
May include a tier of counties north of there to account for
uncertainty. On most guidance, southern tier of counties miss out on
the heavy rain amounts, so may keep the flood watch relatively
small.

Fast responding creeks and streams can be expected to see quick and
significant rises, and if the higher amounts pan out in a particular
basin locally significant and impactful flash flooding could be the
table. On the main stem rivers, streamflows are low and have room
for water so anything more than minor lowland river flooding
developing would be pretty localized.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 2 AM EDT Tuesday for INZ043>047-051>055-
060>063-067>070.

&&

MESOSCALE...Crosbie
AVIATION...50/KF
DISCUSSION...Puma
HYDROLOGY...CP

Hazardous Weather Outlook
National Weather Service Indianapolis IN
233 PM EDT Mon Apr 27 2026

INZ021-028>031-035>049-051>057-060>065-067>072-281845-
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-
233 PM EDT Mon Apr 27 2026

This hazardous weather outlook is for central Indiana.

.DAY ONE...Through Tonight.

Severe thunderstorms are possible through tonight. The main threat
will be damaging straight line winds, although isolated tornadoes
will also be possible. Flooding is also possible. The severe weather
threat will end after midnight.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

More Thunderstorms are possible again on Tuesday Night into Wednesday
morning.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to monitor forecast trends this afternoon and
tonight.

&&

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

JP

Preliminary Local Storm Report
National Weather Service Indianapolis IN
1029 PM EDT Mon Apr 27 2026

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

0957 PM     Tstm Wnd Dmg     2 NE Thorntown          40.15N 86.58W
04/27/2026                   Boone              IN   Amateur Radio

            18 to 20 inch healthy tree limb downed near
            US 52.

&&

AW

Preliminary Local Storm Report
National Weather Service Indianapolis IN
1040 PM EDT Mon Apr 27 2026

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

1024 PM     Tstm Wnd Dmg     2 NE Goldsmith          40.30N 86.13W
04/27/2026                   Tipton             IN   Amateur Radio

            Semi flipped on US 31.

&&

AW

Preliminary Local Storm Report
National Weather Service Indianapolis IN
1042 PM EDT Mon Apr 27 2026

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

0952 PM     Tstm Wnd Dmg     3 N Thorntown           40.17N 86.61W
04/27/2026                   Boone              IN   Amateur Radio

            20 to 24 inch live tree limb downed.

&&

AW

Preliminary Local Storm Report
National Weather Service Indianapolis IN
1043 PM EDT Mon Apr 27 2026

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

1010 PM     Tstm Wnd Dmg     3 N Michigantown        40.37N 86.39W
04/27/2026                   Clinton            IN   Amateur Radio

            18 inch tree downed.

&&

AW

Preliminary Local Storm Report
National Weather Service Indianapolis IN
1044 PM EDT Mon Apr 27 2026

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

1030 PM     Tstm Wnd Gst     4 SW Greentown          40.43N 86.01W
04/27/2026  E70 MPH          Howard             IN   Public

&&

AW

Preliminary Local Storm Report
National Weather Service Indianapolis IN
1052 PM EDT Mon Apr 27 2026

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

0940 PM     Non-Tstm Wnd Dmg Gaston                  40.31N 85.50W
04/27/2026                   Delaware           IN   Fire Dept/Rescue

            Large tree down, expected to be healthy.
            Time estimated from reporter.

&&

KF