Severe Thunderstorm Warning 129, NWS Indianapolis, IN

Area Forecast Discussion
National Weather Service Indianapolis IN
504 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 504 PM EDT Mon Apr 27 2026

Surface analysis shows an outflow boundary associated with ongoing
convective line over south-central IN extending back to near St.
Louis where it meets prefrontal wind shift over central MO. Ongoing
convection has been fueled by moderate instability (MUCAPE 1000-1500
J/KG) and persistent mid level 40-50 kt flow per KIND/KVWX VWPs
associated with convective MCV moving through central IN presently.
As this convective line continues to shift eastward it will continue
to have a threat for damaging winds and marginally severe hail over
scentral IN in the next hour or so while encountering a more hostile
environment with decreasing MUCAPE under 500 J/Kg. The western extent
of the line has become nearly stationary, per vis sat imagery aided
by noteworthy pressure falls over central IL and increasing SW low
level jet. With between 2 and 3 inches of rain already occurring over
far SW portions of central IN, and additional cells training with
additional 1-2 inches of rain along the stationary outflow boundary,
the threat for flash flooding is increasing. Recent CAM guidance
suggests the best threat for significant flash flooding will be in
the Knox, Daviess and Martin county corridor along this boundary
over the next 2-4 hrs.

Significant severe convection recently increasing along prefrontal
trough over central MO will continue to develop into central IL and
eventually back into central IN later this evening (after 00Z). As a
result, areas that were cleared from Severe Thunderstorm watch # 159
are anticipated to be placed in a new watch around that time.
Increasing low level shear (0-1 SRH 300-400 m2/s2) combined with
increasing potential for surface based parcels will lead to a
greater threat for tornadoes, some possibly significant, into
western portions of central IN developing between 00-02Z (8-10 PM
EDT).

&&

.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 (18Z TAF Issuance)...
Issued at 140 PM EDT Mon Apr 27 2026

Impacts:

- S-SE wind gusts 20 to 30 kt with higher gusts in TSRA
- Scattered to numerous thunderstorms through 04Z
- LLWS around 45kt Monday evening/night
- MVFR ceilings Monday evening into early Tuesday

Discussion:

Scattered showers have already developed across western Indiana. A
line of thunderstorms over IL will shift eastward across all but
KLAF this afternoon. IFR vis is expected with this convection along
with a wind shift to the W-NW and gusts from 35-45 kts, lasting less
than 1 hr at all the terminals. In the wake of this line, rain
showers with embedded TS is expected for several hours, before
another round of TSRA moves into the region after 23Z. This second
round of TS activity is expected to end between 03-05Z from west to
east as the cold front pushes eastward with an associated surface
wind shift to the west. MVFR ceilings will linger until Tuesday
morning behind the front.

&&

.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...Crosbie
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
508 PM EDT Mon Apr 27 2026

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

0459 PM     Hail             Seymour                 38.96N 85.89W
04/27/2026  M0.88 Inch       Jackson            IN   Broadcast Media

&&

AW

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

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

0504 PM     Tstm Wnd Gst     2 NE Seymour            38.98N 85.88W
04/27/2026  M60 MPH          Jackson            IN   Public

&&

KF

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

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

0500 PM     Tstm Wnd Dmg     Cortland                38.97N 85.96W
04/27/2026                   Jackson            IN   Emergency Mngr

            Damage to multiple power poles and house
            roofs. Time based on radar.

&&

Crosbie

Special Weather Statement
National Weather Service Indianapolis IN
555 PM EDT Mon Apr 27 2026

INZ021-028>031-035>049-051>057-280000-
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-
Including the cities of Delphi, Flora, Williamsport,
West Lebanon, Lafayette, West Lafayette, Frankfort, Kokomo,
Attica, Covington, Veedersburg, Crawfordsville, Lebanon,
Zionsville, Tipton, Fishers, Carmel, Noblesville, Anderson,
Muncie, Winchester, Union City, Farmland, Parker City, Clinton,
Fairview Park, Rockville, Montezuma, Rosedale, Greencastle,
Plainfield, Brownsburg, Danville, Indianapolis, Greenfield,
New Castle, Terre Haute, Brazil, Spencer, Gosport, Martinsville,
Mooresville, Greenwood, Franklin, Shelbyville, and Rushville
555 PM EDT Mon Apr 27 2026

...Gusty Non-Thunderstorm Winds this Evening...

Non-thunderstorm wind gusts of 30-45 mph, locally higher, will be
possible throughout the evening. Best chances for higher gusts
will be across north-central Indiana.

Secure any outdoor items that may be easily blown about. Drivers of
high profile vehicles may experience increased difficulty while
driving.

Special Weather Statement
National Weather Service Indianapolis IN
556 PM EDT Mon Apr 27 2026

INZ021-028>031-035>049-051>057-280300-
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-
Including the cities of Delphi, Flora, Williamsport,
West Lebanon, Lafayette, West Lafayette, Frankfort, Kokomo,
Attica, Covington, Veedersburg, Crawfordsville, Lebanon,
Zionsville, Tipton, Fishers, Carmel, Noblesville, Anderson,
Muncie, Winchester, Union City, Farmland, Parker City, Clinton,
Fairview Park, Rockville, Montezuma, Rosedale, Greencastle,
Plainfield, Brownsburg, Danville, Indianapolis, Greenfield,
New Castle, Terre Haute, Brazil, Spencer, Gosport, Martinsville,
Mooresville, Greenwood, Franklin, Shelbyville, and Rushville
556 PM EDT Mon Apr 27 2026

...Gusty Non-Thunderstorm Winds this Evening...

Non-thunderstorm wind gusts of 30-45 mph, locally higher, will be
possible throughout the evening. Best chances for higher gusts
will be across north-central Indiana.

Secure any outdoor items that may be easily blown about. Drivers of
high profile vehicles may experience increased difficulty while
driving.

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

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

0452 PM     Tstm Wnd Dmg     Cortland                38.97N 85.96W
04/27/2026                   Jackson            IN   Broadcast Media

            30 power poles down. Time estimated from
            radar.

&&