Iowa, 2017

Hail and Damaging Winds in Iowa, May 17, 2017

May 17, 2017 · NWS DMX · 102 events in 29 counties and zones

After a cold front stalled out across northwest Iowa the previous night, much of Iowa was firmly within the warm sector of an approaching surface low. As a result, winds were strong out of the south, helping keep dew points in the mid to upper 60s.

Where it happened

Every event with a place to put it. Tap one for its entry below.

  • Tornadoes
  • Tropical storms and surge
  • Floods
  • Wind
  • Hail
  • Winter weather
  • Heat and drought
  • Cold
  • Fire, smoke and dust
  • Marine and coastal
  • Other

Open the live radar over this ground

The toll

Deaths
1
Injuries
1
Property damage
$901,000
Crop damage
None recorded
Events
102

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS DMX wrote it up.

After a cold front stalled out across northwest Iowa the previous night, much of Iowa was firmly within the warm sector of an approaching surface low. As a result, winds were strong out of the south, helping keep dew points in the mid to upper 60s. While temperatures were only in the 70s, with the relatively high dew points SBCAPE values were able to eclipse 2000 J/kg in an uncapped environment. Storms began to initiate in the early afternoon, primarily producing funnel clouds and hail. As a weak boundary ahead of the parent cold front moved through, storms organized linearly and became primary wind gust and damaging wind producers as they traveled north/northeast.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Des Moines, IA wrote its last area forecast discussion before the first event at May 17, 11:49 AM CST, 21 minutes earlier.

Area forecast discussion, May 17, 11:49 AM CST, 21 minutes before
Area Forecast Discussion
National Weather Service Des Moines IA
1249 PM CDT Wed May 17 2017

...Updated for 18z Forecast and Aviation Discussions...

.UPDATE...
Issued at 1250 PM CDT Wed May 17 2017

Updated PoPs and sky cover for this afternoon with ongoing trends
and hi-res models. With the issuance of tornado watch 231, have
included severe wording from now through 00z this evening.

17z SPC mesoanalysis shows SBCAPE values of around 2500+J/kg in
the vicinity of the storms over the western part of the CWA
currently north of Denison and Carroll. These storms have moved
into a weaker area of 0-1km and 0-3km SRH values. Hi-res models
handling these well moving them north-northeastward and into
southern Minnesota by around 21z. Attention shifts then back to
the southwest and thunderstorms that will enter southwest Iowa
around 20z and rotate through central Iowa by early this evening.

&&

.SHORT TERM.../Today through Tonight/
Issued at 349 AM CDT Wed May 17 2017

Potential for a very active day including tornadoes across central
Iowa this afternoon into the early evening.  Deep convection late
last evening into the overnight has helped to stabilize the
atmosphere somewhat.  However, strong south flow into the state
continues to help instability regenerate early this morning with
another round of thunderstorms approaching western Iowa at 3 AM. Main
upper system was beginning to lift northeast over the Texas
panhandle and will approach the state this afternoon.

The convection currently approaching the state is expected to remain
largely across the northwest portion of the forecast area through
daybreak into mid morning.  Meanwhile, additional convection
currently across Kansas will race northeast into central Iowa as
moisture surges back northward into the state.  By midday, the main
synoptic front will be near the IA/MN border with the bulk of
convection/precipitation in northern Iowa and areas farther north
and west.  Much of the remainder of central Iowa will be in the warm
sector with surface based capes of 1000-1500J/KG by mid afternoon
along with very good bulk shear of 50kts+ and decent helicity values
of 100-200 m2/s2.  Shorter term models have actually been suggesting
an initial round of strong storms around midday into early afternoon
that should race north across central Iowa, however the main concern
comes by mid to late afternoon as wind shift/trof axis enters
southwest Iowa and races northeast and should provide the focus for
storm development at peak heating.  These storms will likely
initiate around 3-4 pm and with Bunkers motion suggestion movement
around 200@50kt, these storms will be racing quickly north
northeast.  The setup is quite analogous to many of the cooler
season tornado events that occur in Iowa and the likelihood of
tornadoes with these storms seems relatively good and the enhanced
outlook from SPC is in line with expectations at this point.

These storms will likely exit to the north and east by evening with
lingering pcpn in the far north overnight near the deformation zone.
Otherwise, cooler and drier air will spread across the state as
northwest winds increase in the cold advection behind the system.

.LONG TERM.../Thursday through Tuesday/
Issued at 349 AM CDT Wed May 17 2017

Thursday...
At 12z Thu, the upper low which contributed to today's svr wx
potential should be located near the Great Lakes Region. Large-
scale subsidence will be settling in across Iowa behind this
system, serving to keep Thursday dry. 850MB temps drop from near
+15C at 12z this morning, to near +7C at 12z Thu. With CAA in
place and soundings indicating SC field, 10F to 15F drop in temps
from Wed to Thu seems appropriate. If SC deck thick enough to
block sun during much of daytime heating hours, then 15F to 20F
degree drop may be more prudent.

Friday through this weekend...
08z Wed water vapor imagery picking up on deep (538dam heights at
500mb), well-defined upper low spinning over eastern Oregon/SE
Washington. Looking back at the past few 00z/12z model runs,
trends have certainly been slower with the progression of this low
towards the upper Midwest. 00z Wed NAM definitely faster than 00z
Wed ECMWF (slowest) and 00z Wed GFS. The 00z Wed ECMWF did speed
up slightly towards the 00z Wed GFS from the 12z Tue ECMWF. So
feel 00z Wed GFS/ECMWF blend appropriate for tracking this low.
All models depict negative tilting, with the sfc low near SW Iowa
and the 850mb low near NW IA/SE SD by 12z Sat. Ahead of the
system, especially the GFS, smatters the western half of Iowa with
lift driven by reinforcing rounds of theta-e/moisture advection.
Gulf wide open as 850mb LLJ easily taps into moisture source.
PWATs generally in the 1 inch to 1.5 inch range, and forecast
soundings show decent, though certainly not great precip
efficiency potential. In all, expect a widespread, prolonged
period of rain from Friday morning through Saturday afternoon as
cold front doesn't pass through Iowa until 00z- 06Z Sun. SVR
potential nil as best energy only makes it as far north as the
Ozarks.

Large-scale subsidence looks to set in by Sunday. The Canadian
model is an extreme slow outlier as it keeps this system around
through Sunday. Given reliability of Canadian model, cannot
justify leaning towards its solution. Thus, have removed POPs as
best as could be for collaboration purposes on Sunday. Expect
subsequent shifts to remove POPs even further for Sunday into
Monday.

Next Week...
Long-range models struggling with handling track of next upper
low. 00z Wed ECMWF has deep low passing through North Dakota,
where the GFS is void of this feature. Ensemble trends showing
near-normal 850mb temps, so initially thinking near-normal
temperatures in the 70s/50s seem suggested at this time.

&&

.AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/
Issued at 1250 PM CDT Wed May 17 2017

Main concern is timing of thunderstorms that will move through
central Iowa impacting the terminals this afternoon and evening
along with gusty winds. Have tried to time the heavier
thunderstorms with TEMPO groups of just a few hours, though
amendments may be needed to adjust timing as well as conditions.
The thunderstorms will be past most the terminals by mid-evening.
While conditions may improve back into VFR after the storms pass,
clouds are expected to move back in after midnight through
Thursday morning with MVFR ceilings expected over the northern
sites with low VFR ceilings over the southern sites.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

UPDATE...Ansorge
SHORT TERM...Cogil
LONG TERM...Kotenberg
AVIATION...Ansorge
Hazardous weather outlook, May 17, 7:13 AM CST, 4 hours 57 minutes before
Hazardous Weather Outlook
National Weather Service Des Moines IA
813 AM CDT Wed May 17 2017

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-181315-
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-
813 AM CDT Wed May 17 2017

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

There is an enhanced risk for strong to severe thunderstorms this
afternoon and evening. The main threat will be weak, fast-moving,
isolated tornadoes. Damaging winds are the secondary threat, with
large hail and periods of heavy rainfall also possible.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Non-severe thunderstorms are possible Friday through Saturday, as
well as Monday through Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed this afternoon and
evening.

Kotenberg/Zogg

In the hours before

Local storm report, May 17, 6:13 AM CST, 5 hours 57 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
713 AM CDT WED MAY 17 2017

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

1015 PM     HAIL             1 NW ZEARING            42.17N 93.31W
05/16/2017  M1.00 INCH       STORY              IA   CO-OP OBSERVER

&&

CM
Local storm report, May 17, 6:24 AM CST, 5 hours 46 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
724 AM CDT WED MAY 17 2017

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

1055 PM     TSTM WND GST     BEDFORD                 40.67N 94.72W
05/16/2017  E65 MPH          TAYLOR             IA   CO-OP OBSERVER

&&

CM
Local storm report, May 17, 8:37 AM CST, 3 hours 33 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
937 AM CDT WED MAY 17 2017

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

0700 AM     HEAVY RAIN       POCAHONTAS              42.74N 94.66W
05/17/2017  M2.24 INCH       POCAHONTAS         IA   CO-OP OBSERVER

&&

CW
Local storm report, May 17, 10:19 AM CST, 1 hour 51 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1119 AM CDT WED MAY 17 2017

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

0850 PM     TSTM WND DMG     POCAHONTAS              42.74N 94.67W
05/16/2017                   POCAHONTAS         IA   TRAINED SPOTTER

            STRONG WIND AND HEAVY RAIN LAST NIGHT. MANY
            STREETS IN TOWN HAVE TREE BRANCHES DOWN,
            RANGING FROM SMALL STICKS TO BIG, ROUND
            BRANCHES. TREE SNAPPED AT ONE OF OUR
            CEMETERIES ON EAST SIDE OF TOWN. STANDING
            WATER THROUGHOUT TOWN. 3.75 INCHES OF RAIN.
            TIME ESTIMATED BY RADAR.

&&

BSS

The radar

The Des Moines radar (KDMX), 122 km away, was scanning. The volume nearest the first event began at 18:09 UTC.

Open the radar archive at this moment

Event by event

82 thunderstorm wind, 15 hail, 4 funnel cloud, 1 lightning. Local standard time, as filed.

Funnel Cloud, Calhoun

When
May 17, 12:10 PM CST
Where
Calhoun County, 3.76 mi SW of Knoke
Reported by
Social Media
Coordinates
42.480, -94.800

Public reported a funnel cloud via social media.

Funnel Cloud, Sac

When
May 17, 12:40 PM CST
Where
Sac County, 4.57 mi ESE of Nemaha
Reported by
Social Media
Coordinates
42.490, -95.000

Public reported funnel cloud via social media.

Hail, Madison

When
May 17, 1:35 PM CST
Where
Madison County, 1.3 mi NNE of Winterset
Measured
0.75 in hail
Reported by
Public
Coordinates
41.348, -94.013

Funnel Cloud, Tama

When
May 17, 1:40 PM CST
Where
Tama County, 0.86 mi SW of Traer Muni Arpt
Reported by
Social Media
Coordinates
42.190, -92.460

Public reported funnel cloud via social media.

Hail, Dallas

When
May 17, 1:48 PM CST
Where
Dallas County, 1.48 mi SSW of Ortonville
Measured
1 in hail
Reported by
Trained Spotter
Coordinates
41.600, -93.980

Trained spotter reported quarter sized hail.

Hail, Dallas

When
May 17, 1:50 PM CST
Where
Dallas County, 0.86 mi SW of Adel
Measured
0.88 in hail
Reported by
Trained Spotter
Coordinates
41.610, -94.030

Trained spotter reported nickel sized hail.

Hail, Dallas

When
May 17, 1:55 PM CST
Where
Dallas County, 2.14 mi SSW of Dallas Center Arpt
Measured
1 in hail
Reported by
Emergency Manager
Coordinates
41.650, -94.030

Emergency manager reported quarter sized hail.

Hail, Dallas

When
May 17, 2:03 PM CST
Where
Dallas County, 3.47 mi S of Hadden Hill
Measured
1 in hail
Reported by
Trained Spotter
Coordinates
41.570, -93.819

Trained spotter reported quarter sized hail one half mile west of Jordan Creek Mall.

Hail, Polk

When
May 17, 2:08 PM CST
Where
Polk County, 1.24 mi NE of Dodge Fld Arpt
Measured
0.88 in hail
Reported by
Trained Spotter
Coordinates
41.690, -93.700

Trained spotter reported nickel sized hail.

Hail, Polk

When
May 17, 2:10 PM CST
Where
Polk County, 1.38 mi N of Grimes
Measured
1 in hail
Reported by
Trained Spotter
Coordinates
41.700, -93.800

Trained spotter reported quarter sized hail.

Hail, Black Hawk

When
May 17, 2:15 PM CST
Where
Black Hawk County, 2.95 mi NNE of Waterloo
Measured
1 in hail
Reported by
Trained Spotter
Coordinates
42.540, -92.330

Trained spotter reported quarter sized hail.

Hail, Polk

When
May 17, 2:18 PM CST
Where
Polk County, 1.76 mi NE of Herrold
Measured
1 in hail
Reported by
Official NWS Observations
Coordinates
41.736, -93.724

NWS office in Johnston experienced quarter sized hail and wind gusts estimated around 40 to 50 mph.

Thunderstorm Wind, Union

When
May 17, 2:20 PM CST
Where
Union County, 0.52 mi E of Creston Arpt
Measured
52 kt (60 mph) measured gust
Reported by
AWOS
Coordinates
41.020, -94.360

Creston AWOS station recorded a 60 mph wind gust.

Hail, Polk

When
May 17, 2:22 PM CST
Where
Polk County, Polk City
Measured
0.88 in hail
Reported by
Trained Spotter
Coordinates
41.770, -93.720

Trained spotter reported nickel sized hail.

Thunderstorm Wind, Bremer

When
May 17, 2:28 PM CST
Where
Bremer County, 0.86 mi NW of Tripoli
Measured
50 kt (58 mph) estimated gust
Reported by
Public
Coordinates
42.810, -92.260

Public reported 4 inch diameter tree limbs down.

Thunderstorm Wind, Union

When
May 17, 2:30 PM CST
Where
Union County, 0.87 mi SE of Creston
Measured
56 kt (64 mph) measured gust
Reported by
Mesonet
Coordinates
41.060, -94.360

Iowa DOT RWIS site recorded a 64 mph wind gust.

Thunderstorm Wind, Bremer

When
May 17, 2:30 PM CST
Where
Bremer County, 2.31 mi NNW of Schwerin Fld Arpt
Measured
56 kt (64 mph) measured gust
Reported by
Trained Spotter
Coordinates
42.850, -92.190

Trained spotter reported estimated 65 mph wind gusts.

Thunderstorm Wind, Adair

When
May 17, 2:35 PM CST
Where
Adair County, 0.35 mi E of Orient
Measured
52 kt (60 mph) estimated gust
Property damage
$2,000
Reported by
Trained Spotter
Coordinates
41.201, -94.413

Strong winds to 60 mph estimated with tree limbs down in town.

Thunderstorm Wind, Union

When
May 17, 2:39 PM CST
Where
Union County, 0.87 mi SE of Creston
Measured
52 kt (60 mph) estimated gust
Reported by
Emergency Manager
Coordinates
41.060, -94.360

Emergency manager reported tree and tree limb damage in Creston.

Thunderstorm Wind, Adair

When
May 17, 2:40 PM CST
Where
Adair County, 1.27 mi ESE of Adair
Measured
56 kt (64 mph) estimated gust
Property damage
$40,000
Reported by
Emergency Manager
Coordinates
41.493, -94.627

A semi roll-over occurred on I-80 east of Adair due to strong winds.

Thunderstorm Wind, Clarke

When
May 17, 2:43 PM CST
Where
Clarke County, 0.69 mi S of Murray
Measured
61 kt (70 mph) estimated gust
Property damage
$2,000
Reported by
Emergency Manager
Coordinates
41.040, -93.970

Emergency manager stated home owner just west of Murray reported shingles blown off, flag pole snapped, and small tree branches down.

Hail, Story

When
May 17, 2:50 PM CST
Where
Story County, 0.86 mi SW of Ames
Measured
0.75 in hail
Reported by
Storm Chaser
Coordinates
42.020, -93.630

Storm chaser reported penny sized hail.

Thunderstorm Wind, Guthrie

When
May 17, 2:50 PM CST to 3:20 PM CST
Where
Guthrie County, 0.54 mi N of Stuart to 0.97 mi SSE of Jamaica
Measured
64 kt (74 mph) estimated gust
Property damage
$50,000
Reported by
Emergency Manager
Coordinates
41.508, -94.318

Emergency manager reported numerous instances across Guthrie County to the Adair County line of wind damage. This included 40x60 machine shed roof taken off 4 miles SW of Panora, power lines down in Jamaica from blown over tree, power lines down in Stuart due to tree damage.

Thunderstorm Wind, Adair

When
May 17, 2:55 PM CST
Where
Adair County, 8.22 mi NE of Howe
Measured
60 kt (69 mph) estimated gust
Property damage
$40,000
Reported by
Emergency Manager
Coordinates
41.493, -94.281

Emergency manager reported numerous instances across Guthrie County to the Adair County line of wind damage. This included 2 modular offices blown off I-80 2 miles east of Stuart.

Thunderstorm Wind, Madison

When
May 17, 2:55 PM CST
Where
Madison County, 1.29 mi NNE of Winterset
Measured
52 kt (60 mph) estimated gust
Reported by
Public
Coordinates
41.348, -94.013

Small to medium limbs down in town.

Thunderstorm Wind, Dallas

When
May 17, 3:00 PM CST
Where
Dallas County, 3.62 mi NE of Linden
Measured
56 kt (64 mph) estimated gust
Property damage
$40,000
Reported by
Emergency Manager
Coordinates
41.688, -94.222

Emergency manager reported semi blown over into the ditch at the intersection of P46 and Highway 44.

Thunderstorm Wind, Crawford

When
May 17, 3:00 PM CST
Where
Crawford County, 2.14 mi NNW of Manilla
Measured
52 kt (60 mph) estimated gust
Property damage
$5,000
Reported by
Emergency Manager
Coordinates
41.910, -95.260

Emergency manager reported damage to an outbuilding.

Thunderstorm Wind, Madison

When
May 17, 3:02 PM CST
Where
Madison County, 5.9 mi NNW of Bevington
Measured
52 kt (60 mph) estimated gust
Reported by
Trained Spotter
Coordinates
41.450, -93.840

Trained spotter reported winds estimated 50 to 60 mph.

Thunderstorm Wind, Warren

When
May 17, 3:07 PM CST
Where
Warren County, 0.52 mi E of Cumming
Measured
52 kt (60 mph) estimated gust
Property damage
$5,000
Reported by
Public
Coordinates
41.480, -93.760

Public reported shingles blown off homes.

Thunderstorm Wind, Dallas

When
May 17, 3:10 PM CST to 3:25 PM CST
Where
Dallas County, 0.51 mi E of Dawson to 4.24 mi NNE of Shuler Mine
Measured
60 kt (69 mph) estimated gust
Property damage
$50,000
Reported by
Emergency Manager
Coordinates
41.850, -94.220

Emergency manager reported power poles blown down on Highway 44, semi truck blownn over at intersection of P46 and Highway 141. All between Perry and Dawson.

Thunderstorm Wind, Madison

When
May 17, 3:10 PM CST
Where
Madison County, 9.31 mi E of Earlham
Measured
61 kt (70 mph) estimated gust
Property damage
$10,000
Reported by
Trained Spotter
Coordinates
41.500, -93.950

Trained spotter reported tree trunks snapped.

Thunderstorm Wind, Dallas

When
May 17, 3:11 PM CST
Where
Dallas County, 1.19 mi W of Hadden Hill
Measured
52 kt (60 mph) estimated gust
Reported by
NWS Employee
Coordinates
41.621, -93.853

Five to six inch tree branches down near the road.

Thunderstorm Wind, Dallas

When
May 17, 3:12 PM CST
Where
Dallas County, 1.06 mi ESE of Shuler Mine
Measured
52 kt (60 mph) estimated gust
Reported by
NWS Employee
Coordinates
41.626, -93.860

NWS employee reported wind gusts of 60 mph. Sturdy lawn chairs blownn across the lawn as well.

Thunderstorm Wind, Dallas

When
May 17, 3:12 PM CST
Where
Dallas County, 3.17 mi SSE of Hadden Hill
Measured
56 kt (64 mph) estimated gust
Reported by
NWS Employee
Coordinates
41.579, -93.802

NWS employee reported upwards of 65 mph wind gusts at home location.

Thunderstorm Wind, Polk

When
May 17, 3:14 PM CST
Where
Polk County, 0.52 mi E of (Dsm)des Moines Intl
Measured
52 kt (60 mph) measured gust
Reported by
ASOS
Coordinates
41.530, -93.660

Des Moines International Airport ASOS recorded a 60 mph wind gust.

Thunderstorm Wind, Polk

When
May 17, 3:14 PM CST
Where
Polk County, 0.58 mi ENE of Ashawa
Measured
56 kt (64 mph) estimated gust
Property damage
$10,000
Reported by
Emergency Manager
Coordinates
41.585, -93.761

Emergency manager reported multiple trees and power lines down in West Des Moines along Ashworth Rd.

Thunderstorm Wind, Warren

When
May 17, 3:15 PM CST
Where
Warren County, 0.69 mi S of Indianola
Measured
50 kt (58 mph) estimated gust
Reported by
Emergency Manager
Coordinates
41.360, -93.570

Emergency manager reported numerous tree branches of 3 inch diameter and greater down. Still have rain and some gusts to 50 to 60 mph. Time estimated by radar.

Thunderstorm Wind, Polk

When
May 17, 3:15 PM CST
Where
Polk County, 0.44 mi NNE of Clover Hills
Measured
54 kt (62 mph) estimated gust
Reported by
NWS Employee
Coordinates
41.606, -93.747

NWS employee recorded 62 mph wind gust on home weather station.

Thunderstorm Wind, Lucas

When
May 17, 3:15 PM CST
Where
Lucas County, 0.52 mi E of Chariton Muni Arpt
Measured
53 kt (61 mph) measured gust
Reported by
AWOS
Coordinates
41.020, -93.360

Chariton AWOS recorded a 61 mph wind gust.

Thunderstorm Wind, Polk

When
May 17, 3:15 PM CST
Where
Polk County, 1.03 mi W of Clive
Measured
51 kt (59 mph) measured gust
Reported by
Mesonet
Coordinates
41.630, -93.800

KCCI School Net recorded a 59 mph wind gust.

Hail, Monroe

When
May 17, 3:15 PM CST
Where
Monroe County, Hocking
Measured
1 in hail
Reported by
Emergency Manager
Coordinates
40.980, -92.820

Emergency manager reported quarter sized hail.

Thunderstorm Wind, Polk

When
May 17, 3:16 PM CST
Where
Polk County, 0.52 mi E of Ft Des Moines
Measured
51 kt (59 mph) measured gust
Reported by
Mesonet
Coordinates
41.530, -93.620

KCCI School Net site recorded a 59 mph wind gust.

Thunderstorm Wind, Polk

When
May 17, 3:18 PM CST
Where
Polk County, 2.49 mi SE of Lovington
Measured
61 kt (70 mph) estimated gust
Property damage
$5,000
Reported by
Trained Spotter
Coordinates
41.630, -93.660

Trained spotter reported 12 to 13 inch diameter tree snapped with branches in the street. Time estimated by radar.

Thunderstorm Wind, Warren

When
May 17, 3:18 PM CST
Where
Warren County, 0.86 mi NW of Cumming
Measured
56 kt (64 mph) estimated gust
Property damage
$40,000
Reported by
Emergency Manager
Coordinates
41.490, -93.780

Emergency manager reported semi blown over on I-35 at mile marker 65.

Thunderstorm Wind, Warren

When
May 17, 3:18 PM CST
Where
Warren County, Norwalk
Measured
61 kt (70 mph) estimated gust
Reported by
Emergency Manager
Coordinates
41.480, -93.680

Emergency manager reported wind gusts of 60 to 70 mph.

Thunderstorm Wind, Polk

When
May 17, 3:18 PM CST
Where
Polk County, 1.38 mi S of Ashawa
Measured
56 kt (64 mph) estimated gust
Reported by
Public
Coordinates
41.560, -93.770

Public reported tree damage including 6 to 12 inch diameter limbs torn off main trunk.

Thunderstorm Wind, Polk

When
May 17, 3:19 PM CST
Where
Polk County, 0.69 mi N of Grimes
Measured
61 kt (70 mph) estimated gust
Reported by
NWS Employee
Coordinates
41.690, -93.800

NWS employee reported wind gusts to 70 mph. Trees and large branches were down around town.

Thunderstorm Wind, Dallas

When
May 17, 3:19 PM CST
Where
Dallas County, 0.76 mi NE of Dallas Center to 4.79 mi N of Hadden Hill
Measured
56 kt (64 mph) estimated gust
Property damage
$20,000
Reported by
Emergency Manager
Coordinates
41.688, -93.961

Emergency manager reported power lines down between Dallas Center and Grimes. Dallas Center without power at the time of the report.

Thunderstorm Wind, Warren

When
May 17, 3:20 PM CST
Where
Warren County, 2.76 mi S of Ackworth
Measured
52 kt (60 mph) estimated gust
Reported by
Public
Coordinates
41.330, -93.480

Public reported tree damage, wind speeds unknown at the time. Time estimated by radar.

Hail, Monroe

When
May 17, 3:20 PM CST
Where
Monroe County, 1.67 mi SSW of Hocking
Measured
0.88 in hail
Reported by
Trained Spotter
Coordinates
40.957, -92.828

A trained spotter reported nickel size hail in southern Monroe County.

Funnel Cloud, Monroe

When
May 17, 3:20 PM CST
Where
Monroe County, 1.67 mi SSW of Hocking
Reported by
Trained Spotter
Coordinates
40.957, -92.828

Thunderstorm Wind, Polk

When
May 17, 3:21 PM CST
Where
Polk County, 1.69 mi ENE of Herrold
Measured
56 kt (64 mph) estimated gust
Reported by
NWS Employee
Coordinates
41.730, -93.720

NWS employee reported tree branches down on Beaver Dr and power outages in Johnston.

Thunderstorm Wind, Kossuth

When
May 17, 3:21 PM CST
Where
Kossuth County, 3.02 mi E of Burt
Measured
65 kt (75 mph) estimated gust
Reported by
Public
Coordinates
43.200, -94.160

Public reported 70 to 80 estimated wind gusts. Time estimated by radar.

Thunderstorm Wind, Polk

When
May 17, 3:22 PM CST
Where
Polk County, 1.77 mi SW of Capitol Hgts
Measured
52 kt (60 mph) estimated gust
Reported by
Public
Coordinates
41.605, -93.578

Public reported tree damage on Easton Blvd near 22nd St. Time estimated by radar.

Thunderstorm Wind, Polk

When
May 17, 3:24 PM CST
Where
Polk County, 0.08 mi ENE of Saylorville
Measured
56 kt (64 mph) estimated gust
Reported by
Amateur Radio
Coordinates
41.681, -93.629

A 65 mph gust was measured on a home weather station, and 3 inch tree branches were reported down.

Thunderstorm Wind, Polk

When
May 17, 3:25 PM CST
Where
Polk County, 1.03 mi E of Urbandale
Measured
56 kt (64 mph) estimated gust
Reported by
Public
Coordinates
41.630, -93.700

Public reported large tree split near its base and landed across the roadway. Time estimated by radar and this is a delayed report.

Thunderstorm Wind, Polk

When
May 17, 3:25 PM CST
Where
Polk County, 0.87 mi SSW of Des Moines
Measured
61 kt (70 mph) estimated gust
Reported by
Trained Spotter
Coordinates
41.589, -93.627

Trained spotter reported evacuation of tall buildings in Capital Square underway. Very strong winds downtown, estimated around 70 mph.

Thunderstorm Wind, Polk

When
May 17, 3:25 PM CST to 3:40 PM CST
Where
Polk County, 1.65 mi NNW of Urbandale to 1.89 mi W of Avon
Measured
61 kt (70 mph) estimated gust
Property damage
$100,000
Reported by
Emergency Manager
Coordinates
41.651, -93.734

Emergency manager stated dozens of reports of power lines down, trees down, power outages from transformer damage, and motor vehicle crashes all suspected to be storm related. Metro wide reports too numerous to report.

Thunderstorm Wind, Boone

When
May 17, 3:25 PM CST to 3:50 PM CST
Where
Boone County, 0.51 mi E of Napier to 1.9 mi ENE of Ogden
Measured
60 kt (69 mph) estimated gust
Property damage
$75,000
Reported by
Emergency Manager
Coordinates
41.980, -93.720

Emergency manager reported multiple farmsteads with roofs blown off, damage to several outbuildings, a garage blown off the foundation, and power lines down. The roof and upper levels of an old corn crib were blown off, windows broken from debris blowing into the window, a garage door was ripped off the track, 6 inch diameter tree limbs were down, large trees were down blocking a road. Another large tree limb landed on a van and porch roof destroying the van and roof.

Thunderstorm Wind, Polk

When
May 17, 3:28 PM CST
Where
Polk County, 1.7 mi WSW of Capitol Hgts
Measured
52 kt (60 mph) estimated gust
Reported by
Trained Spotter
Coordinates
41.610, -93.580

Trained spotter estimated wind gusts to around 60 mph, with minor tree damage in the area.

Hail, Monroe

When
May 17, 3:29 PM CST
Where
Monroe County, 1.04 mi E of Albia
Measured
1 in hail
Reported by
Fire Department/Rescue
Coordinates
41.030, -92.800

Fire Chief reported quarter sized hail in Albia.

Thunderstorm Wind, Polk

When
May 17, 3:30 PM CST
Where
Polk County, 1.24 mi NW of Altoona
Measured
50 kt (58 mph) measured gust
Reported by
Mesonet
Coordinates
41.660, -93.490

Altoona RWIS measured wind gusts to 58 mph.

Thunderstorm Wind, Marion

When
May 17, 3:36 PM CST
Where
Marion County, 1.81 mi SSE of Pleasantville
Measured
52 kt (60 mph) measured gust
Reported by
Emergency Manager
Coordinates
41.355, -93.262

Emergency manager reported 60 mph wind gusts at Highway 5 and Highway 92.

Thunderstorm Wind, Marion

When
May 17, 3:38 PM CST
Where
Marion County, 2.45 mi S of Pleasantville
Measured
52 kt (60 mph) estimated gust
Property damage
$5,000
Reported by
Trained Spotter
Coordinates
41.345, -93.263

Large willow tree downed in the yard.

Thunderstorm Wind, Jasper

When
May 17, 3:39 PM CST
Where
Jasper County, 5.17 mi W of Monroe
Measured
61 kt (70 mph) estimated gust
Reported by
Public
Coordinates
41.520, -93.200

Public reported wind gusts to 70 mph.

Thunderstorm Wind, Jasper

When
May 17, 3:40 PM CST
Where
Jasper County, 1.24 mi NE of Colfax
Measured
52 kt (60 mph) estimated gust
Reported by
Trained Spotter
Coordinates
41.680, -93.230

Trained spotter reported strong winds to 60 mph with heavy rainfall approaching.

Thunderstorm Wind, Story

When
May 17, 3:44 PM CST
Where
Story County, 1.72 mi NW of Ames
Measured
52 kt (60 mph) estimated gust
Reported by
Trained Spotter
Coordinates
42.050, -93.640

Trained spotter reported strong winds to around 60 mph or more.

Thunderstorm Wind, Mahaska

When
May 17, 3:45 PM CST
Where
Mahaska County, 0.52 mi E of Oskaloosa
Measured
56 kt (64 mph) estimated gust
Reported by
Social Media
Coordinates
41.300, -92.640

Public reported large tree downed in town. Report via social media and is a delayed report.

Thunderstorm Wind, Marion

When
May 17, 3:51 PM CST
Where
Marion County, 0.86 mi SE of Pella
Measured
56 kt (64 mph) measured gust
Reported by
Mesonet
Coordinates
41.410, -92.920

RWIS station on IA 163 recorded 65 mph wind gust.

Thunderstorm Wind, Webster

When
May 17, 4:00 PM CST
Where
Webster County, 0.69 mi N of Ft Dodge
Measured
51 kt (59 mph) measured gust
Reported by
Mesonet
Coordinates
42.510, -94.180

RWIS station near Fort Dodge on US 20 recorded a 59 mph wind gust.

Lightning, Story

When
May 17, 4:00 PM CST
Where
Story County, Roland
Property damage
$25,000
Reported by
Trained Spotter
Coordinates
42.170, -93.500

Trained spotter reported a lightning strike that hit a tree, resulting in the tree falling onto and damaging the house.

Thunderstorm Wind, Marshall

When
May 17, 4:03 PM CST to 4:13 PM CST
Where
Marshall County, 0.86 mi SE of Marshalltown to 0.59 mi ESE of Haverhill
Measured
60 kt (69 mph) estimated gust
Property damage
$20,000
Reported by
Emergency Manager
Coordinates
42.040, -92.910

Emergency manager reported roof damage to a farmstead and a barn blown down near the Marshalltown airport.

Thunderstorm Wind, Marshall

When
May 17, 4:08 PM CST
Where
Marshall County, 0.86 mi SE of Marshalltown
Measured
56 kt (64 mph) estimated gust
Reported by
Public
Coordinates
42.040, -92.910

Public reported several large trees down.

Thunderstorm Wind, Marshall

When
May 17, 4:11 PM CST
Where
Marshall County, 1.24 mi SE of Marshalltown
Measured
52 kt (60 mph) estimated gust
Reported by
Trained Spotter
Coordinates
42.040, -92.900

Trained spotter reported wind gusts to 60 mph.

Thunderstorm Wind, Marshall

When
May 17, 4:12 PM CST to 4:20 PM CST
Where
Marshall County, 0.86 mi SE of Marshalltown to 2.09 mi ESE of Liscomb
Measured
61 kt (70 mph) estimated gust
Property damage
$100,000
Reported by
Emergency Manager
Coordinates
42.040, -92.910

Emergency manager reported tree on a large propane tank near Liscomb on Oaks Ave, many trees and power lines down in Marshalltown, traffic lights down in Marshalltown, and a barn down.

Thunderstorm Wind, Marshall

When
May 17, 4:12 PM CST
Where
Marshall County, 0.69 mi S of Marshalltown Arpt
Measured
60 kt (69 mph) measured gust
Reported by
ASOS
Coordinates
42.110, -92.920

Marshalltown airport ASOS recorded a 69 mph wind gust.

Thunderstorm Wind, Marshall

When
May 17, 4:12 PM CST
Where
Marshall County, 1.33 mi WSW of Marshalltown
Measured
56 kt (64 mph) measured gust
Property damage
$2,000
Reported by
Amateur Radio
Coordinates
42.041, -92.943

A 3 foot diameter tree was uprooted.

Thunderstorm Wind, Marshall

When
May 17, 4:13 PM CST
Where
Marshall County, 0.86 mi SE of Marshalltown
Measured
51 kt (59 mph) measured gust
Reported by
Mesonet
Coordinates
42.040, -92.910

RWIS on US 30 recorded at 59 mph wind gust.

Thunderstorm Wind, Webster

When
May 17, 4:13 PM CST
Where
Webster County, 2.63 mi NE of (Fod)ft Dodge Muni A
Measured
50 kt (58 mph) estimated gust
Reported by
Trained Spotter
Coordinates
42.580, -94.148

Some medium to large limbs were downed by the winds.

Thunderstorm Wind, Marshall

When
May 17, 4:13 PM CST
Where
Marshall County, 1.55 mi E of Albion
Measured
60 kt (69 mph) measured gust
Property damage
$15,000
Reported by
Emergency Manager
Coordinates
42.123, -92.970

The Emergency Manager reported grain bins destroyed and roof damage to a house.

Thunderstorm Wind, Marshall

When
May 17, 4:14 PM CST
Where
Marshall County, 1.69 mi ESE of Albion
Measured
60 kt (69 mph) estimated gust
Property damage
$5,000
Reported by
Trained Spotter
Coordinates
42.110, -92.970

Trained spotter reported doors blown off machine shed and large branches down.

Thunderstorm Wind, Marshall

When
May 17, 4:19 PM CST
Where
Marshall County, 0.86 mi SE of Marshalltown
Measured
51 kt (59 mph) measured gust
Reported by
Mesonet
Coordinates
42.040, -92.910

RWIS on Highway 30 measured wind gusts to 59 mph.

Thunderstorm Wind, Poweshiek

When
May 17, 4:25 PM CST
Where
Poweshiek County, 2.18 mi WSW of Grinnell Arpt
Measured
59 kt (68 mph) measured gust
Reported by
AWOS
Coordinates
41.710, -92.740

Marshalltown airport AWOS recorded 68 mph wind gust.

Thunderstorm Wind, Grundy

When
May 17, 4:28 PM CST
Where
Grundy County, 0.65 mi SSW of Grundy Center
Measured
56 kt (64 mph) estimated gust
Property damage
$10,000
Reported by
Social Media
Coordinates
42.361, -92.773

Public reported 1 to 2 foot diameter trees down near the courthouse. Report via social media and is a delayed report.

Thunderstorm Wind, Grundy

When
May 17, 4:30 PM CST
Where
Grundy County, Holland
Measured
61 kt (70 mph) estimated gust
Property damage
$10,000
Reported by
Social Media
Coordinates
42.400, -92.800

Public reported outbuilding blown apart. Report via social media and is a delayed report.

Thunderstorm Wind, Wapello

When
May 17, 4:35 PM CST
Where
Wapello County, 0.6 mi N of Agency
Measured
51 kt (59 mph) estimated gust
Reported by
Trained Spotter
Coordinates
40.989, -92.372

Trained spotter reported an estimated gust of around 60 mph.

Thunderstorm Wind, Black Hawk

When
May 17, 4:38 PM CST
Where
Black Hawk County, 0.32 mi SSW of Eagle Center
Measured
56 kt (64 mph) estimated gust
Reported by
Department of Highways
Coordinates
42.326, -92.533

Iowa DOT reported tree across IA-175 blocking road east of Reinbeck between T69 and D46. Time estimated by radar and is a delayed report.

Thunderstorm Wind, Butler

When
May 17, 4:40 PM CST to 5:00 PM CST
Where
Butler County, 0.32 mi WNW of Aplington to 0.64 mi SSW of Greene
Measured
65 kt (75 mph) estimated gust
Injuries
1 direct, 0 indirect
Property damage
$100,000
Reported by
Emergency Manager
Coordinates
42.583, -92.885

A machine shed was blown down on top of a person, who was extricated and taken to the hospital. A building in Greene collapsed and caused a gas leak. Widespread tree damage and numerous trees down, power lines down and building damage throughout the western half of the county.

Thunderstorm Wind, Butler

When
May 17, 4:43 PM CST
Where
Butler County, 1.72 mi NW of Kesley
Measured
52 kt (60 mph) estimated gust
Reported by
Trained Spotter
Coordinates
42.690, -92.940

Trained spotter reported wind gusts to 60 mph.

Thunderstorm Wind, Butler

When
May 17, 4:43 PM CST
Where
Butler County, 2.04 mi E of Aplington to 0.32 mi WNW of Aplington
Measured
56 kt (64 mph) estimated gust
Property damage
$10,000
Reported by
Amateur Radio
Coordinates
42.580, -92.840

Amateur radio reported several power poles/power lines down between Parkersburg and Aplington on Highway 57.

Thunderstorm Wind, Butler

When
May 17, 4:45 PM CST to 4:53 PM CST
Where
Butler County, 0.69 mi N of Parkersburg to 1.94 mi WSW of New Hartford
Measured
65 kt (75 mph) estimated gust
Deaths
1 direct, 0 indirect
Property damage
$60,000
Reported by
COOP Observer
Coordinates
42.580, -92.780

Coop observer reported very high winds estimated at over 70 mph. Power reported out in Parkersburg, semi overturned on Highway 57 resulting in one fatality, and numerous tree limbs down on roads. A 3 foot diameter tree also downed in Parkersburg.

Thunderstorm Wind, Butler

When
May 17, 4:45 PM CST
Where
Butler County, 0.69 mi N of Aplington
Measured
52 kt (60 mph) estimated gust
Reported by
Trained Spotter
Coordinates
42.590, -92.880

Trained spotter reported 4 inch diameter tree limbs down along with numerous other smaller branches in Aplington.

Thunderstorm Wind, Black Hawk

When
May 17, 4:47 PM CST
Where
Black Hawk County, 1.47 mi SSE of Cedar Falls
Measured
61 kt (70 mph) estimated gust
Reported by
Public
Coordinates
42.500, -92.440

Public estimated wind gusts to at least 70 mph.

Thunderstorm Wind, Butler

When
May 17, 4:47 PM CST
Where
Butler County, 1.01 mi W of Allison
Measured
61 kt (70 mph) estimated gust
Reported by
Emergency Manager
Coordinates
42.750, -92.800

Emergency manager estimated wind gusts to 70 mph.

Hail, Wapello

When
May 17, 4:49 PM CST
Where
Wapello County, 2.61 mi W of Eldon
Measured
1 in hail
Reported by
Fire Department/Rescue
Coordinates
40.920, -92.220

Local fire department estimated hail nickel to quarter in size.

Thunderstorm Wind, Black Hawk

When
May 17, 4:51 PM CST
Where
Black Hawk County, 2.76 mi N of Cedar Falls Jct
Measured
56 kt (64 mph) measured gust
Reported by
Amateur Radio
Coordinates
42.470, -92.416

A 65 mph wind gust was recorded at a home weather station.

Thunderstorm Wind, Black Hawk

When
May 17, 4:53 PM CST
Where
Black Hawk County, 0.51 mi E of Cedar Falls
Measured
56 kt (64 mph) estimated gust
Property damage
$15,000
Reported by
Public
Coordinates
42.520, -92.440

Public reported a tree fell on their house. Time estimated by radar.

Thunderstorm Wind, Butler

When
May 17, 4:53 PM CST
Where
Butler County, Parkersburg
Measured
61 kt (70 mph) estimated gust
Reported by
Amateur Radio
Coordinates
42.570, -92.780

Amateur radio reported wind gusts to 70 mph.

Thunderstorm Wind, Black Hawk

When
May 17, 4:53 PM CST
Where
Black Hawk County, 0.69 mi N of (Alo)waterloo Muni A
Measured
61 kt (70 mph) measured gust
Reported by
ASOS
Coordinates
42.560, -92.400

Waterloo Airport ASOS recorded 70 mph wind gust.

Thunderstorm Wind, Hancock

When
May 17, 5:00 PM CST
Where
Hancock County, 0.5 mi E of Garner
Measured
56 kt (64 mph) estimated gust
Property damage
$20,000
Reported by
Social Media
Coordinates
43.100, -93.610

Public reported a large tree fell on a house and damage was done to a fence in town. Tree was 1 to 2 feet in diameter. Reported via social media and is a delayed report.

Thunderstorm Wind, Bremer

When
May 17, 5:00 PM CST
Where
Bremer County, 0.51 mi W of Plainfield
Measured
56 kt (64 mph) measured gust
Reported by
Mesonet
Coordinates
42.850, -92.540

RWIS near Plainfield recorded a 65 mph wind gust.

Thunderstorm Wind, Black Hawk

When
May 17, 5:18 PM CST
Where
Black Hawk County, 1.37 mi ENE of (Alo)waterloo Muni A
Measured
56 kt (64 mph) estimated gust
Property damage
$10,000
Reported by
Emergency Manager
Coordinates
42.561, -92.377

Emergency manager estimated 6 inch diameter tree limb down pinning people in a car. Numerous locations in North Waterloo with smaller limbs down on streets and cars.

The people who died

As the offices recorded each death: direct deaths were caused by the weather itself, indirect ones by something it set in motion.

EventDateAgeSexWhereKind
Thunderstorm Wind, Butler2017-05-1770MaleVehicle/Towed TrailerDirect

What these are

Funnel Cloud
A rotating column of cloud extending from a thunderstorm that did not reach the ground.
Hail
Hail three-quarters of an inch or larger, or smaller hail that caused damage, filed with the largest stone measured.
Thunderstorm Wind
Winds from a thunderstorm of 50 knots (58 mph) or more, or lower winds that caused damage or casualties. Measured gusts are marked MG, estimated EG.
Lightning
A lightning strike that killed, injured or caused damage.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in Iowa in 2017Every state in 2017This day in weather historyWarnings in Iowa, May 2017

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 698182, 698184, 699715, 698185, 698186, 698187, 698188, 698189, 698190, 698191, 698192, 698194, 698195, 698196, 698197, 698199, 698200, 699924, 698203, 699710, 698205, 698206, 699711, 698204, 699716, 698207, 698208, 698209, 698210, 698211, 698220, 699910, 698212, 698214, 698216, 698217, 698215, 698218, 698221, 698224, and more.