Severe Thunderstorm Warning 85, NWS Des Moines, IA

Area Forecast Discussion
National Weather Service Des Moines IA
101 PM CDT Fri Apr 17 2026

.KEY MESSAGES...

- Enhanced Risk (level 3 of 5) in eastern Iowa. All severe
  hazards, including large hail, damaging wind, and tornadoes,
  are possible with storms today.

- Much cooler this weekend with overnight lows in the 20s and 30s.

- Mild and dry to start the week with thunderstorms returning to
  the forecast by late week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 101 PM CDT Fri Apr 17 2026

The surface low early this afternoon is centered across north
central Iowa with attendant sharp cold front pushing across the
state. The impact was already being felt this morning in
northwest Iowa when Estherville fell from 71 degrees at 10am to
43 degrees by 10:07am. Early convection has bubbled in northern
Iowa and into Minnesota associated with lift in the vicinity of
the surface low. The cold air sharply undercuts the warm and
deeply unstable air in place with the primary trough farther to
the west. This will allow for a period of some post-frontal
elevated storm development, something already noted with
elevated showers in northwest Iowa this morning behind the
surface front. Across the state two primary ares of convective
development are anticipated into the afternoon, noted in midday
satellite imagery. The first is pre-frontal convection
developing in an area of convergence noted in surface
observations across eastern Iowa and visible in a plume of
cumulus. A second line of cumulus trails along the cold front
across western Iowa that will push across Iowa through the rest
of the afternoon.

Much of the prefrontal convection is expected to develop east of the
area, perhaps clipping far southeastern parts of the area near
Ottumwa. There is plenty of available instability with 3000-4000
J/kg of MUCAPE (3000+ MLCAPE) and steep mid level lapse rates of 8+
C/km. Much of this instability is elevated with very little in
the lowest 3 km (<100 J/kg). This will limit low level
stretching and some of the tornado potential locally, though it
is certainly NOT eliminated. The steep mid-level lapse rates,
along with well curved hodographs in the low levels will help
with rotating updrafts and hail growth. Storms are expected to
quickly grow upscale. As this happens the initial discrete
development will become multi-cell to linear as it pushes east,
transitioning to a damaging with threat with tornado potential
along the line.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 101 PM CDT Fri Apr 17 2026

Much colder air pushes in with the cold front as temperatures fall
into the 30s tonight. Saturday remains breezy with continued cold
air advection and the enhanced pressure gradient across the area.
Temperatures in the upper 40s north to mid 50s south with 20-25
mph wind through the day. By Sunday winds relax with
temperatures warming slightly into the 50s to low 60s. The
thermal ridge builds next week, bringing 70s back to the area.
Much of the week is dry with storm chances returning late in
the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1236 PM CDT Fri Apr 17 2026

Breezy southerly winds are increasing across the area ahead of a
strong cold front moving across the state today with gusts of
25-30 kts. The front will sweep through this afternoon, exiting
east after 00z. Early storms have bubbled across northern Iowa
this morning and may come near KMCW in the next hour or so,
however recent trends indicate this should miss KMCW so have
kept from that TAF at this time. The main line of storms will
develop in east central Iowa. This may come near KDSM and KALO,
however satellite shows initiation should be just east of those
sites so have removed mentions from those sites. KOTM will see
the bulk of thunderstorm activity this afternoon from around
19-20z through 00s.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

SHORT TERM...Hagenhoff
LONG TERM...Hagenhoff
AVIATION...Hagenhoff

Hazardous Weather Outlook
National Weather Service Des Moines IA
438 AM CDT Fri Apr 17 2026

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-180945-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
438 AM CDT Fri Apr 17 2026

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

There is an Enhanced Risk (Level 3 of 5) for severe thunderstorms
across southeast Iowa on Friday. There is a Slight Risk (Level 2
of 5) for severe storms more into central Iowa. Damaging winds
and tornadoes are the primary threats. Large hail is also
possible, especially early in the event.

Additional rises on rivers and streams, with localized minor
flooding possible. Ponding and low-end flash flooding is also
possible, especially in urban areas.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Freezing temperatures are expected in northern Iowa Friday night
and across much of the area Saturday night.

Thunderstorm chances return Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotters will be needed this afternoon.

Preliminary Local Storm Report
National Weather Service Des Moines IA
227 PM CDT Fri Apr 17 2026

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

0225 PM     Hail             1 E Knoxville           41.32N 93.08W
04/17/2026  E1.00 Inch       Marion             IA   Emergency Mngr

&&

MD

Preliminary Local Storm Report
National Weather Service Des Moines IA
235 PM CDT Fri Apr 17 2026

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

0226 PM     Hail             3 SSW Mitchellville     41.62N 93.39W
04/17/2026  E1.00 Inch       Polk               IA   Trained Spotter

&&

TR

Preliminary Local Storm Report
National Weather Service Des Moines IA
237 PM CDT Fri Apr 17 2026

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

0205 PM     Hail             2 NW Cumming            41.50N 93.79W
04/17/2026  E0.50 Inch       Warren             IA   Public

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

&&

JR/BH

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Preliminary Local Storm Report
National Weather Service Des Moines IA
240 PM CDT Fri Apr 17 2026

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

0204 PM     Hail             3 SE Saylorville        41.65N 93.60W
04/17/2026  E1.00 Inch       Polk               IA   Public

            Report from mPING: Quarter (1.00 in.).

0205 PM     Hail             3 E Saylorville         41.68N 93.57W
04/17/2026  E1.25 Inch       Polk               IA   Public

            Reported by Trained Spotter.

&&

Preliminary Local Storm Report
National Weather Service Des Moines IA
241 PM CDT Fri Apr 17 2026

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

0237 PM     Funnel Cloud     2 N Parkersburg         42.60N 92.78W
04/17/2026                   Butler             IA   Public

            multiple reports of a thin funnel cloud
            north side of Parkersburg.

&&