Hail and Damaging Winds in Iowa, July 21, 2008

Name: Hail and Damaging Winds in Iowa, July 21, 2008
Start: 2008-07-21T00:14
End: 2008-07-21T03:29
Location: Iowa

July 21, 2008 · NWS DMX · 81 events in 11 counties and zones

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: 0
Injuries: 0
Property damage: $1.5 million
Crop damage: $950,000
Events: 81

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.

A very unstable situation set up during the afternoon and evening of the 20th as a frontal boundary and remnants of the outflow boundary was established across southern Iowa. Temperatures warmed into the low to mid 90s across southern Iowa along and just south of the boundary. Dewpoint readings soared into the mid 70s to low 80s by evening. This resulted in very unstable CAPE values in the 5000 to 5500 J/kg range, and lifted indices of -10 to -13 C. during the evening. A low level jet of 40 kts set up while the atmosphere showed fairly strong shear, in the 40 to 55 kt range. There wasn't as much deep moisture as had been present in previous days with 1.3 to 1.6 inches of precipitable water. The freezing level remained quite high at around 14,600 feet and CAPE in the -10 to -30 C. layer of the atmosphere was only 300 to 500 J/kg. Downdraft CAPE was considerable however with 1000 to 1500 J/kg available. The LCL was also higher than it had been the previous day and was between 1500 and 2000 meters. During the evening, thunderstorms formed rapidly over northern Nebraska and far southern South Dakota to the north of the boundary. By late evening, additional development took place across Iowa. For the most part, these storms remained just below severe levels. One of them produced one and one quarter inch diameter hail over central Iowa however. The main event was the MCC from Nebraska. The MCC moved into Iowa after midnight and produced high winds and hail as it moved through. A portion of the system became a Derecho over west central Iowa and advanced across the state during the early morning hours. Winds of 60 to 75 MPH were common, with a few gusts estimated as high as 100 MPH in central Iowa. A radio tower was blown over by the winds in the Dawson area of Dallas County. Tree damage was very extensive from the winds with local utilities reporting as many as 200,000 homes were without power following the passage of the system. In Jamaica, in Guthrie County, 50 percent of the trees in town were damaged with 30 trees completely down. The roof was damaged at the race track there. The Guthrie County mobile EOC was tossed 150 feet into a field and roads were impassible. In Polk County, in Ankeny, 20 tO 30 Black Locust trees of 1 to 2 feet in diameter were snapped or uprooted near the intersection of 35th street and Highway 415. Winds estimated at 100 MPH in Dawson, in Dallas County, caused considerable damage. Roads were blocked by trees, with heavy equipment required to clear them. LP tanks were leaking in town as they were thrown about and damaged by trees. The grain elevator in town was also damaged. Bulldozers were also required to clear streets of tree damage in Boone County at Madrid. In Polk County, at Mitchellville, the roof was taken off of a modular building at the Mitchellville Correctional Facility. Lightning struck a house west of Nevada in Story County, setting it on fire. A second house was struck by lightning in Poweshiek County in Montezuma. Minor damage was reported to the building.

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 Jul 20, 11:10 PM CST, 1 hour 4 minutes earlier.

Area forecast discussion, Jul 20, 11:10 PM CST, 1 hour 4 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1210 AM CDT MON JUL 21 2008

...UPDATED FOR AVIATION...

.DISCUSSION...
.SHORT TERM /REST OF THIS AFTERNOON THROUGH TONIGHT/...
STRONG LOW LEVEL CAP IN PLACE NEAR 900-850 MB THIS AFTERNOON NORTH
OF SFC WARM FRONT WHICH IS NEARLY STAGNANT OVER SRN NEBRASKA AND
NORTHERN MISSOURI. SOME ELEVATED INSTABILITY THOUGH IS BEING
REALIZED DUE TO WARM ADVECTION OVER WRN IA WHERE SHOWERS AND A FEW
BENIGN THUNDERSTORMS HAVE DEVELOPED...AND THIS ACTIVITY SHOULD
REMAIN RATHER UNEVENTFUL FOR MUCH OF THE AFTERNOON...THOUGH AN ISOLD
SVR STORM IS POSSIBLE GIVEN OVERALL INSTABILITY. WILL BE DIFFICULT
TO GENERATE SFC BASED THUNDERSTORMS THROUGH MUCH OF THE AFTERNOON
DUE TO AFOREMENTIONED CAP AND ANY ORGANIZED ACTIVITY WILL LIKELY
AWAIT SUPPORT FROM THE INCREASING LOW LEVEL JET. ONCE STORMS DO
FORM...SOME TRAINING IS LIKELY FROM WEST TO EAST ALONG THE 850 MB
BOUNDARY THROUGH CNTRL IA WITH THE POTENTIAL FOR HEAVY RAINFALL.

MORE SIGNIFICANT UPPER LEVEL DYNAMICS STILL REMAIN UPSTREAM WHERE A
PAIR OF UPPER LEVEL TROUGHS WILL SOON CONSOLIDATE BEFORE MOVING
TOWARDS THE MIDWEST OVERNIGHT. THIS CONSOLIDATION WILL RESULT IN
STRENGTHENING OF THE UPPER LEVEL JET AND ENHANCED UPPER LEVEL
DIVERGENCE IN THE RIGHT EXIT REGION OF THE JET...WHICH COMBINED WITH
STRONG SHORT WAVE ENERGY AT 500 MB SHOULD BE SUFFICIENT TO SUSTAIN A
SEVERE MCS ACROSS NEBRASKA AND SOUTH DAKOTA MOVING INTO IOWA AFTER
MIDNIGHT. POTENTIAL FOR A DERECHO TYPE EVENT MOVING THROUGH AFTER
06Z ALONG WITH ADDITIONAL HEAVY RAINFALL OVER AREAS THAT HAVE BEEN
SOAKED THE PAST THREE DAYS. HAVE THUS ISSUED A FLASH FLOOD WATCH FOR
TONIGHT FOR PORTIONS OF CNTRL IA.

.LONG TERM /MONDAY THROUGH SUNDAY/...
ONCE THE MCS CLEARS OUT BY MID MORNING THINGS WILL QUIET DOWN FOR
SEVERAL HOURS...BUT SOME ADDITIONAL PRECIP MAY THEN DEVELOP NEAR THE
850 MB WARM FRONT OVER SOUTHERN IA SO WILL MAINTAIN SLIGHT
CHANCE/CHANCE POPS IN THE SOUTH MONDAY AFTERNOON/NIGHT. STRONG TO
SEVERE STORMS ARE A POSSIBILITY HERE...HOWEVER IT APPEARS UNLIKELY
THAT INSTABILITY WILL BE ABLE TO RECOVER ENOUGH FOR THIS.
THEREAFTER...HIGH PRESSURE BUILDING INTO THE UPPER MIDWEST/GREAT
LAKES WILL SHOVE THE BOUNDARY SOUTH OF OUR AREA BY TUESDAY
MORNING...WITH GFS TAKING IT DOWN TO AROUND TOPEKA AND NAM AND ECMWF
KEEPING IT JUST BARELY TO OUR SOUTHWEST. IN ANY EVENT THE HIGH
PRESSURE WILL DOMINATE CENTRAL IA PROVIDING QUIETER WEATHER TUESDAY
AND WEDNESDAY.

AS A MID LEVEL RIDGE PASSES THROUGH THE MIDWEST WEDNESDAY NIGHT...A
SURFACE TROUGH WILL CARRY THE OLD BOUNDARY THROUGH FROM THE WEST
PROVIDING HIGHER RAIN CHANCES. HAVE BUMPED POPS UP TO AROUND 40 WED
NIGHT/THURS AS FORECAST MODELS HAVE BEEN FAIRLY CONSISTENT WITH THIS
SCENARIO. SEVERE WEATHER WILL BE A POSSIBILITY HERE AS WE SHOULD BE
ABLE TO DESTABILIZE WITH SOUTHEASTERLY FLOW ON THE BACKSIDE OF THE
DEPARTING SFC HIGH...AND WNW MID LEVEL FLOW WILL PROVIDE SOME SHEAR
FOR STORMS TO WORK WITH. ONCE THIS SYSTEM WORKS THROUGH BY LATE
THURSDAY WE WILL ONCE AGAIN BE IN NORTHWESTERLY FLOW WITH SLIGHTLY
BELOW NORMAL TEMPERATURES AND LOWER RAIN CHANCES THROUGH THE WEEKEND.

&&

.AVIATION...21/06Z

CONVECTION NOW DEVELOPING RAPIDLY ALONG A KFOD-KDSM-KOTM LINE AND
EXPECT THIS TREND TO CONTINUE OVER THE NEXT SEVERAL HOURS. SEVER
WEATHER ENVIRONMENT IN PLACE OVERNIGHT...AND EXPECT LARGER LINE OF
STORM OVER NORTHWEST IOWA TO MOVE THROUGH THE AREA OVERNIGHT. HAVE
TEMPOS OD SEVERE WIND GUSTS AT KFOD-KDSM AND KOTM IN THE 7-11 UTC
TIMEFRAME.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...FLASH FLOOD WATCH IN EFFECT FOR
CENTRAL IOWA...BETWEEN HIGHWAYS 3 AND 92...UNTIL 7 AM CDT MONDAY.

&&

LONG TERM...LEE
SHORT TERM/AVIATION...DONAVON/RUSSELL

Hazardous weather outlook, Jul 20, 2:31 PM CST, 9 hours 43 minutes before

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
331 PM CDT SUN JUL 20 2008

IAZ023>028-033>039-044>050-058>062-212045-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-GUTHRIE-DALLAS-POLK-JASPER-POWESHIEK-
331 PM CDT SUN JUL 20 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR MUCH OF CENTRAL IOWA BETWEEN
HIGHWAY 3 AND HIGHWAY 92.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS ARE POSSIBLE THROUGH MID EVENING WITH A
FEW SEVERE STORMS POSSIBLE WITH THE PRIMARY THREAT BEING QUARTER
SIZED HAIL. MORE SIGNIFICANT THUNDERSTORMS ARE ANTICIPATED TO
DEVELOP AFTER 10 PM. QUARTER SIZED HAIL AND DAMAGING WINDS TO 70
MPH ARE POSSIBLE WITH THIS ACTIVITY ALONG WITH ISOLATED TORNADOES.

IN ADDITION...VERY HEAVY RAINFALL IS POSSIBLE WITH THE OVERNIGHT
ACTIVITY WITH THE POTENTIAL FOR ONE TO THREE INCHES OF RAIN OVER A
SHORT PERIOD OF TIME. THIS RAINFALL ALONG WITH SATURATED SOILS
FROM RECENT HEAVY RAINS WILL CREATE THE POTENTIAL FOR FLASH FLOODING.

A FLASH FLOOD WATCH IS IN EFFECT FOR THE AREA TONIGHT. PLEASE REFER TO
THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A FEW SEVERE THUNDERSTORMS ARE POSSIBLE MONDAY. ADDITIONAL
CHANCES FOR THUNDERSTORMS ARE IN THE FORECAST FOR WEDNESDAY THROUGH
THURSDAY...WITH WEDNESDAY NIGHT BEING THE NEXT BEST CHANCE FOR A
LARGE COMPLEX OF THUNDERSTORMS AND ATTENDANT SEVERE WEATHER.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED TONIGHT ESPECIALLY OVERNIGHT.
RAINFALL REPORTS WOULD ALSO BE APPRECIATED.

IAZ057-070>075-081>086-092>097-212045-
AUDUBON-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-
CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-
APPANOOSE-DAVIS-
331 PM CDT SUN JUL 20 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THERE IS A SLIGHT RISK FOR SEVERE WEATHER THROUGH THE PERIOD. THE
GREATEST POTENTIAL FOR A FEW SEVERE STORMS IS AFTER 10 PM TONIGHT.
QUARTER SIZED HAIL AND DAMAGING WINDS TO 65 MPH ARE THE PRIMARY
THREATS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MONDAY. DAMAGING
WINDS AND LARGE HAIL ARE THE MAIN THREATS. LOCALLY HEAVY RAINFALL
MAY LEAD TO PONDING WATER AND SHORT TERM RISES ON AREA STREAMS AND
CREEKS. ADDITIONAL CHANCES FOR THUNDERSTORMS ARE IN THE FORECAST
FOR WEDNESDAY NIGHT AND THURSDAY...WITH WEDNESDAY NIGHT BEING THE
NEXT BEST CHANCE FOR A LARGE COMPLEX OF THUNDERSTORMS AND
ATTENDANT SEVERE WEATHER.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE TONIGHT ESPECIALLY AFTER 10 PM.

IAZ004>007-015>017-212045-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
331 PM CDT SUN JUL 20 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THERE IS A SLIGHT RISK FOR SEVERE WEATHER THROUGH THE PERIOD. THE
GREATEST POTENTIAL FOR A FEW SEVERE STORMS IS AFTER 10 PM TONIGHT.
QUARTER SIZED HAIL AND DAMAGING WINDS TO 65 MPH ARE THE PRIMARY
THREATS.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

ISOLATED NON SEVERE THUNDERSTORMS ARE POSSIBLE MONDAY. ADDITIONAL
CHANCES FOR THUNDERSTORMS ARE IN THE FORECAST FOR WEDNESDAY NIGHT
AND THURSDAY...WITH WEDNESDAY NIGHT BEING THE NEXT BEST CHANCE
FOR A LARGE COMPLEX OF THUNDERSTORMS AND ATTENDANT SEVERE WEATHER.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE TONIGHT ESPECIALLY AFTER 10 PM.

DONAVON

In the hours before

Local storm report, Jul 20, 9:39 PM CST, 2 hours 35 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DES MOINES IA
1039 PM CDT SUN JUL 20 2008

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

0945 PM     HAIL             3 WNW DES MOINES        41.60N 93.67W
07/19/2008  E1.00 INCH       POLK               IA   PUBLIC

            DELAYED REPORT

&&

BMOYER

The radar

The Des Moines radar (KDMX), 21 km away, was scanning. The volume nearest the first event began at 06:13 UTC.

Open the radar archive at this moment

Event by event

68 thunderstorm wind, 11 hail, 2 lightning. Local standard time, as filed.

Hail, Dallas

When: July 21, 12:14 AM CST
Where: Dallas County, 3.72 mi SE of Minburn
Measured: 1.25 in hail
Property damage: $5,000
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.740, -93.970

Hail, Polk

When: July 21, 12:39 AM CST
Where: Polk County, 0.86 mi SW of Rider
Measured: 0.88 in hail
Property damage: $1,000
Crop damage: $10,000
Reported by: Law Enforcement
Coordinates: 41.660, -93.790

Thunderstorm Wind, Crawford

When: July 21, 12:50 AM CST
Where: Crawford County, Denison
Measured: 65 kt (75 mph) estimated gust
Property damage: $25,000
Crop damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.020, -95.350

Numerous trees down across Denison and across Crawford County.

Thunderstorm Wind, Carroll

When: July 21, 1:05 AM CST
Where: Carroll County, 2.47 mi SE of Arcadia
Measured: 56 kt (64 mph) estimated gust
Property damage: $3,000
Reported by: Trained Spotter
Coordinates: 42.060, -95.010

Thunderstorm Wind, Carroll

When: July 21, 1:05 AM CST
Where: Carroll County, 3.49 mi S of Breda
Measured: 61 kt (70 mph) estimated gust
Property damage: $5,000
Reported by: Trained Spotter
Coordinates: 42.130, -94.990

Thunderstorm Wind, Carroll

When: July 21, 1:20 AM CST
Where: Carroll County, 2.76 mi S of Dedham
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.860, -94.820

Thunderstorm Wind, Carroll

When: July 21, 1:23 AM CST
Where: Carroll County, 0.69 mi S of Glidden
Measured: 66 kt (76 mph) measured gust
Property damage: $25,000
Crop damage: $50,000
Reported by: Mesonet
Coordinates: 42.060, -94.730

From a KCCI schoolnet site.

Thunderstorm Wind, Carroll

When: July 21, 1:25 AM CST
Where: Carroll County, 2.76 mi S of Dedham
Measured: 61 kt (70 mph) estimated gust
Property damage: $15,000
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.860, -94.820

Trained spotter reported widespread power line damage in the Carroll area.

Thunderstorm Wind, Carroll

When: July 21, 1:26 AM CST
Where: Carroll County, 3.49 mi S of Breda
Measured: 61 kt (70 mph) estimated gust
Property damage: $5,000
Reported by: Trained Spotter
Coordinates: 42.130, -94.990

Thunderstorm Wind, Carroll

When: July 21, 1:28 AM CST
Where: Carroll County, 2.47 mi SE of Arcadia
Measured: 56 kt (64 mph) estimated gust
Property damage: $3,000
Reported by: Trained Spotter
Coordinates: 42.060, -95.010

Thunderstorm Wind, Carroll

When: July 21, 1:28 AM CST
Where: Carroll County, 0.69 mi S of Glidden
Measured: 68 kt (78 mph) measured gust
Property damage: $25,000
Crop damage: $50,000
Reported by: Mesonet
Coordinates: 42.060, -94.730

Measured wind by KCCI schoolnet site.

Thunderstorm Wind, Guthrie

When: July 21, 1:30 AM CST
Where: Guthrie County, 0.51 mi E of Bayard
Measured: 65 kt (75 mph) estimated gust
Property damage: $25,000
Crop damage: $10,000
Reported by: Emergency Manager
Coordinates: 41.850, -94.560

Power was out in town with fires caused by limbs on power lines.

Thunderstorm Wind, Guthrie

When: July 21, 1:35 AM CST
Where: Guthrie County, Bagley
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Emergency Manager
Coordinates: 41.850, -94.430

Several trees down and power was out in town.

Thunderstorm Wind, Guthrie

When: July 21, 1:40 AM CST
Where: Guthrie County, 2.07 mi NE of Panora
Measured: 55 kt (63 mph) measured gust
Property damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.720, -94.500

Tree damage also reported.

Thunderstorm Wind, Greene

When: July 21, 1:43 AM CST
Where: Greene County, 1 mi SW of Scranton
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Public
Coordinates: 42.020, -94.564

Thunderstorm Wind, Greene

When: July 21, 1:44 AM CST
Where: Greene County, 0.69 mi S of Scranton
Measured: 61 kt (70 mph) estimated gust
Property damage: $20,000
Crop damage: $10,000
Reported by: Law Enforcement
Coordinates: 42.020, -94.550

Numerous trees down due to very high winds.

Thunderstorm Wind, Greene

When: July 21, 1:44 AM CST
Where: Greene County, Scranton
Measured: 65 kt (75 mph) estimated gust
Property damage: $20,000
Crop damage: $5,000
Reported by: Newspaper
Coordinates: 42.030, -94.550

Thunderstorm Wind, Guthrie

When: July 21, 1:45 AM CST
Where: Guthrie County, 0.51 mi E of Jamaica
Measured: 80 kt (92 mph) estimated gust
Property damage: $75,000
Crop damage: $50,000
Reported by: Emergency Manager
Coordinates: 41.850, -94.310

Three to four foot diameter trees were down with roads impassable. A travel trailer was blown approximately 150 feet.

Thunderstorm Wind, Guthrie

When: July 21, 1:45 AM CST
Where: Guthrie County, Guthrie Center
Measured: 70 kt (81 mph) estimated gust
Property damage: $25,000
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.680, -94.500

Power was out with numerous tree limbs down, one was 18 inches in diameter. A swing set was picked up and rolled across the yard.

Thunderstorm Wind, Dallas

When: July 21, 1:49 AM CST
Where: Dallas County, 0.86 mi SE of Dawson
Measured: 58 kt (67 mph) measured gust
Property damage: $15,000
Reported by: Broadcast Media
Coordinates: 41.840, -94.220

From a KCCI television viewer.

Thunderstorm Wind, Guthrie

When: July 21, 1:50 AM CST
Where: Guthrie County, 2.07 mi NE of Panora
Measured: 55 kt (63 mph) measured gust
Property damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.720, -94.500

Tree damage also reported.

Thunderstorm Wind, Guthrie

When: July 21, 1:50 AM CST
Where: Guthrie County, 0.51 mi E of Jamaica
Measured: 65 kt (75 mph) estimated gust
Property damage: $10,000
Reported by: Emergency Manager
Coordinates: 41.850, -94.310

A 4 inch flag pole was bent by the wind. Power was reported out as well.

Thunderstorm Wind, Guthrie

When: July 21, 1:50 AM CST
Where: Guthrie County, 0.51 mi E of Jamaica
Measured: 75 kt (86 mph) estimated gust
Property damage: $150,000
Crop damage: $75,000
Reported by: Emergency Manager
Coordinates: 41.850, -94.310

Significant tree damage in town with 50 percent of the trees damaged. Thirty trees were down, two sheds had roof damage and the county mobile EOC was tossed 150 feet into the field.

Thunderstorm Wind, Guthrie

When: July 21, 1:52 AM CST
Where: Guthrie County, 5.74 mi NNE of Monteith
Measured: 52 kt (60 mph) measured gust
Property damage: $3,000
Reported by: Mesonet
Coordinates: 41.700, -94.370

Measured gust from KCCI schoolnet site.

Thunderstorm Wind, Dallas

When: July 21, 1:52 AM CST
Where: Dallas County, 0.86 mi SE of Dawson
Measured: 87 kt (100 mph) estimated gust
Property damage: $100,000
Crop damage: $75,000
Reported by: Trained Spotter
Coordinates: 41.840, -94.220

Numerous trees were uprooted with only one road remaining open in town. Three homes had trees down on them. A few LP tanks were leaking due to tree damage and a grain elevator sustained damage in town.

Hail, Story

When: July 21, 1:57 AM CST
Where: Story County, 0.44 mi NW of Ames
Measured: 1.75 in hail
Property damage: $10,000
Crop damage: $5,000
Reported by: Trained Spotter
Coordinates: 42.035, -93.626

An ISU Meteorology professor reported mainly one half inch to nickel size hail with a few up to golf ball size.

Thunderstorm Wind, Dallas

When: July 21, 1:59 AM CST to 2:09 AM CST
Where: Dallas County, 1.24 mi NE of Perry
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Amateur Radio
Coordinates: 41.840, -94.100

Damaging wind lasted 10 minutes and was still in progress.

Hail, Dallas

When: July 21, 2:00 AM CST
Where: Dallas County, 0.69 mi N of Woodward
Measured: 0.88 in hail
Property damage: $1,000
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.860, -93.930

Thunderstorm Wind, Greene

When: July 21, 2:00 AM CST
Where: Greene County, 0.51 mi W of Grand Jct
Measured: 75 kt (86 mph) estimated gust
Property damage: $50,000
Crop damage: $50,000
Reported by: Amateur Radio
Coordinates: 42.030, -94.240

Numerous trees were down, some up to 2 feet in diameter. Power was out, especially widespread in rural areas.

Thunderstorm Wind, Dallas

When: July 21, 2:02 AM CST
Where: Dallas County, 1.24 mi NE of Perry
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Amateur Radio
Coordinates: 41.840, -94.100

Numerous large trees down.

Hail, Story

When: July 21, 2:04 AM CST
Where: Story County, 0.86 mi SW of Ames
Measured: 0.75 in hail
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 42.020, -93.630

Thunderstorm Wind, Dallas

When: July 21, 2:05 AM CST
Where: Dallas County, 0.86 mi SE of Dawson
Measured: 70 kt (81 mph) estimated gust
Property damage: $25,000
Crop damage: $75,000
Reported by: Trained Spotter
Coordinates: 41.840, -94.220

Numerous trees were downed and power lines along Highway 141 from Jamaica to Perry. Tree damage also in Dawson.

Hail, Story

When: July 21, 2:06 AM CST
Where: Story County, 0.86 mi SW of Ames
Measured: 0.88 in hail
Crop damage: $5,000
Reported by: Law Enforcement
Coordinates: 42.020, -93.630

Hail, Story

When: July 21, 2:07 AM CST
Where: Story County, 0.86 mi SW of Ames
Measured: 1 in hail
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 42.020, -93.630

Thunderstorm Wind, Boone

When: July 21, 2:08 AM CST
Where: Boone County, Ogden
Measured: 61 kt (70 mph) estimated gust
Property damage: $50,000
Crop damage: $5,000
Reported by: Newspaper
Coordinates: 42.030, -94.030

Thunderstorm Wind, Dallas

When: July 21, 2:09 AM CST
Where: Dallas County, 1.24 mi NE of Perry
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Amateur Radio
Coordinates: 41.840, -94.100

One foot diameter tree down with other widespread tree damage.

Hail, Story

When: July 21, 2:10 AM CST
Where: Story County, 0.86 mi SW of Ames
Measured: 0.88 in hail
Property damage: $2,000
Crop damage: $5,000
Reported by: Amateur Radio
Coordinates: 42.020, -93.630

Thunderstorm Wind, Dallas

When: July 21, 2:10 AM CST
Where: Dallas County, 0.52 mi W of Dallas Center
Measured: 70 kt (81 mph) estimated gust
Property damage: $100,000
Crop damage: $50,000
Reported by: Law Enforcement
Coordinates: 41.680, -93.980

Highway 44 in Dallas Center was blocked due to tree limbs down across the road. Several homes were damaged by falling limbs.

Thunderstorm Wind, Dallas

When: July 21, 2:11 AM CST
Where: Dallas County, 0.52 mi W of Dallas Center
Measured: 56 kt (64 mph) estimated gust
Property damage: $5,000
Reported by: Amateur Radio
Coordinates: 41.680, -93.980

Thunderstorm Wind, Dallas

When: July 21, 2:12 AM CST
Where: Dallas County, 0.86 mi SE of Dawson
Measured: 87 kt (100 mph) estimated gust
Property damage: $50,000
Crop damage: $50,000
Reported by: Law Enforcement
Coordinates: 41.840, -94.220

Numerous trees uprooted.

Thunderstorm Wind, Dallas

When: July 21, 2:13 AM CST
Where: Dallas County, 0.86 mi SE of Dawson
Measured: 87 kt (100 mph) estimated gust
Property damage: $75,000
Crop damage: $50,000
Reported by: Law Enforcement
Coordinates: 41.840, -94.220

Trained spotters reported winds estimated at 100 MPH with numerous trees uprooted in Dawson.

Thunderstorm Wind, Dallas

When: July 21, 2:14 AM CST
Where: Dallas County, 0.69 mi N of Woodward
Measured: 52 kt (60 mph) measured gust
Property damage: $3,000
Reported by: Mesonet
Coordinates: 41.860, -93.930

Measured wind from a KCCI schoolnet site.

Thunderstorm Wind, Dallas

When: July 21, 2:14 AM CST
Where: Dallas County, 1.24 mi NE of Perry
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Law Enforcement
Coordinates: 41.840, -94.100

Trees down in town.

Thunderstorm Wind, Dallas

When: July 21, 2:15 AM CST
Where: Dallas County, 0.52 mi W of Dallas Center
Measured: 61 kt (70 mph) estimated gust
Property damage: $15,000
Reported by: Law Enforcement
Coordinates: 41.680, -93.980

Dallas County Law Enforcement reported winds of 70 MPH in Dallas Center.

Thunderstorm Wind, Polk

When: July 21, 2:16 AM CST to 2:21 AM CST
Where: Polk County, 2.07 mi S of Polk City
Measured: 61 kt (70 mph) measured gust
Property damage: $5,000
Reported by: NWS Employee
Coordinates: 41.740, -93.720

Winds at the NWS office were measured at 70 MPH with small hail. Winds lasted 5 minutes and were still going on.

Hail, Polk

When: July 21, 2:18 AM CST
Where: Polk County, Polk City
Measured: 0.88 in hail
Property damage: $1,000
Crop damage: $5,000
Reported by: Amateur Radio
Coordinates: 41.770, -93.720

Thunderstorm Wind, Polk

When: July 21, 2:18 AM CST
Where: Polk County, Polk City
Measured: 61 kt (70 mph) estimated gust
Property damage: $5,000
Reported by: Amateur Radio
Coordinates: 41.770, -93.720

Thunderstorm Wind, Boone

When: July 21, 2:20 AM CST
Where: Boone County, 1.54 mi E of Madrid
Measured: 75 kt (86 mph) estimated gust
Property damage: $25,000
Crop damage: $50,000
Reported by: Law Enforcement
Coordinates: 41.880, -93.820

Extensive large tree limbs blown off trees. Bulldozer will be needed to clear streets.

Thunderstorm Wind, Polk

When: July 21, 2:21 AM CST
Where: Polk County, 1.72 mi NE of Johnston
Measured: 57 kt (66 mph) estimated gust
Property damage: $5,000
Reported by: Storm Chaser
Coordinates: 41.690, -93.680

One foot diameter tree branch was blocking the road.

Thunderstorm Wind, Polk

When: July 21, 2:22 AM CST
Where: Polk County, 0.86 mi SE of Ankeny
Measured: 65 kt (75 mph) estimated gust
Property damage: $50,000
Crop damage: $25,000
Reported by: Amateur Radio
Coordinates: 41.720, -93.610

Numerous 4 to 6 inch branches down. One 14 inch branch down. Fifty percent of the town without power.

Thunderstorm Wind, Story

When: July 21, 2:23 AM CST
Where: Story County, 2.07 mi SE of Slater
Measured: 61 kt (70 mph) estimated gust
Property damage: $15,000
Reported by: Law Enforcement
Coordinates: 41.860, -93.650

Tree uprooted and fell on an LP tank at a farmstead between Slater and Alleman.

Hail, Polk

When: July 21, 2:25 AM CST
Where: Polk County, 1.47 mi NNE of Ankeny
Measured: 0.75 in hail
Crop damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.750, -93.610

Thunderstorm Wind, Polk

When: July 21, 2:25 AM CST
Where: Polk County, 0.86 mi SW of Des Moines
Measured: 55 kt (63 mph) measured gust
Property damage: $10,000
Reported by: Mesonet
Coordinates: 41.590, -93.630

Report received from KCCI schoolnet site.

Thunderstorm Wind, Polk

When: July 21, 2:25 AM CST
Where: Polk County, 1.69 mi WSW of Oralabor
Measured: 70 kt (81 mph) estimated gust
Property damage: $100,000
Crop damage: $50,000
Reported by: Public
Coordinates: 41.720, -93.660

Twenty to 30 Black Locust trees 1 to 2 feet in diameter and 50 to 60 feet tall were downed or snapped off. A few were uprooted at the intersection of 35th St. and Highway 415. Trees were on top of a house as well.

Thunderstorm Wind, Polk

When: July 21, 2:26 AM CST
Where: Polk County, 0.3 mi NNE of Windsor Hgts
Measured: 63 kt (72 mph) measured gust
Property damage: $5,000
Reported by: NWS Employee
Coordinates: 41.604, -93.718

Thunderstorm Wind, Polk

When: July 21, 2:26 AM CST
Where: Polk County, 2.07 mi S of Polk City
Measured: 62 kt (71 mph) measured gust
Property damage: $5,000
Reported by: NWS Employee
Coordinates: 41.740, -93.720

Thunderstorm Wind, Dallas

When: July 21, 2:27 AM CST
Where: Dallas County, 3.17 mi SSE of Hadden Hill
Measured: 52 kt (60 mph) estimated gust
Property damage: $1,000
Reported by: Trained Spotter
Coordinates: 41.580, -93.800

Thunderstorm Wind, Dallas

When: July 21, 2:27 AM CST
Where: Dallas County, 0.69 mi N of Woodward
Measured: 65 kt (75 mph) estimated gust
Property damage: $25,000
Crop damage: $30,000
Reported by: Trained Spotter
Coordinates: 41.860, -93.930

A trained spotter reported whole trees down in Woodward with wind gusts to around 75 MPH. Also, dime to nickel size hail fell at approximately 0200 CDT.

Thunderstorm Wind, Polk

When: July 21, 2:28 AM CST
Where: Polk County, 0.86 mi SE of Ankeny
Measured: 61 kt (70 mph) estimated gust
Property damage: $5,000
Reported by: Trained Spotter
Coordinates: 41.720, -93.610

Thunderstorm Wind, Polk

When: July 21, 2:28 AM CST
Where: Polk County, 0.95 mi NW of Ft Des Moines
Measured: 61 kt (70 mph) estimated gust
Property damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.541, -93.641

Winds from 60 to 70 MPH near the intersection of 18th and McKinley Ave.

Thunderstorm Wind, Polk

When: July 21, 2:28 AM CST
Where: Polk County, 1.24 mi NW of Urbandale
Measured: 64 kt (74 mph) measured gust
Property damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.640, -93.740

Tree damage reported as well.

Thunderstorm Wind, Dallas

When: July 21, 2:28 AM CST
Where: Dallas County, 0.52 mi W of Dallas Center
Measured: 65 kt (75 mph) estimated gust
Property damage: $15,000
Crop damage: $25,000
Reported by: Amateur Radio
Coordinates: 41.680, -93.980

Large trees down at Highway 44 and 15th Street. Other tree damage throughout town.

Thunderstorm Wind, Dallas

When: July 21, 2:28 AM CST
Where: Dallas County, 0.69 mi S of Minburn
Measured: 61 kt (70 mph) estimated gust
Property damage: $15,000
Reported by: Law Enforcement
Coordinates: 41.760, -94.030

Significant tree and power pole damage. Several trees blocked.

Thunderstorm Wind, Warren

When: July 21, 2:29 AM CST
Where: Warren County, 1.38 mi N of Norwalk
Measured: 52 kt (60 mph) estimated gust
Property damage: $1,000
Reported by: Public
Coordinates: 41.500, -93.680

Lawn furniture was blown away.

Thunderstorm Wind, Polk

When: July 21, 2:35 AM CST
Where: Polk County, 0.86 mi SE of Ankeny
Measured: 53 kt (61 mph) measured gust
Property damage: $2,000
Reported by: Mesonet
Coordinates: 41.720, -93.610

Thunderstorm Wind, Jasper

When: July 21, 2:44 AM CST
Where: Jasper County, 0.86 mi NE of Colfax
Measured: 65 kt (75 mph) estimated gust
Property damage: $25,000
Crop damage: $25,000
Reported by: Amateur Radio
Coordinates: 41.680, -93.240

Numerous trees and limbs down. Power was out all the way north to Interstate 80.

Thunderstorm Wind, Jasper

When: July 21, 2:45 AM CST
Where: Jasper County, 0.86 mi SW of Prairie City
Measured: 61 kt (70 mph) estimated gust
Property damage: $5,000
Reported by: Trained Spotter
Coordinates: 41.590, -93.240

Thunderstorm Wind, Jasper

When: July 21, 2:45 AM CST
Where: Jasper County, 0.52 mi W of Prairie City
Measured: 56 kt (64 mph) measured gust
Property damage: $10,000
Reported by: Trained Spotter
Coordinates: 41.600, -93.240

Numerous trees and tree limbs down with power out.

Thunderstorm Wind, Polk

When: July 21, 2:45 AM CST
Where: Polk County, 3.68 mi E of Santiago to 1.82 mi E of Santiago
Measured: 70 kt (81 mph) estimated gust
Property damage: $25,000
Crop damage: $10,000
Reported by: Law Enforcement
Coordinates: 41.660, -93.360

Roof blown off of a modular building at the Mitchellville Correctional Facility.

Hail, Jasper

When: July 21, 2:48 AM CST
Where: Jasper County, 1.03 mi E of Colfax
Measured: 1 in hail
Property damage: $5,000
Crop damage: $10,000
Reported by: Amateur Radio
Coordinates: 41.670, -93.230

Winds of 60 MPH as well.

Thunderstorm Wind, Jasper

When: July 21, 2:48 AM CST
Where: Jasper County, 1.03 mi E of Colfax
Measured: 52 kt (60 mph) estimated gust
Property damage: $3,000
Reported by: Amateur Radio
Coordinates: 41.670, -93.230

Thunderstorm Wind, Jasper

When: July 21, 2:48 AM CST
Where: Jasper County, 0.52 mi W of Prairie City
Measured: 56 kt (64 mph) measured gust
Property damage: $5,000
Reported by: Trained Spotter
Coordinates: 41.600, -93.240

Lightning, Story

When: July 21, 2:49 AM CST
Where: Story County, 0.51 mi W of Nevada
Property damage: $20,000
Reported by: Fire Department/Rescue
Coordinates: 42.020, -93.460

House was set on fire due to lightning strike.

Thunderstorm Wind, Jasper

When: July 21, 2:51 AM CST
Where: Jasper County, 0.69 mi N of Baxter
Measured: 51 kt (59 mph) measured gust
Property damage: $1,000
Reported by: Mesonet
Coordinates: 41.830, -93.150

Report from a KCCI schoolnet site.

Thunderstorm Wind, Jasper

When: July 21, 2:58 AM CST
Where: Jasper County, 1.03 mi E of Newton
Measured: 50 kt (58 mph) measured gust
Property damage: $1,000
Reported by: Mesonet
Coordinates: 41.700, -93.030

Report received from a KCCI schoolnet site.

Thunderstorm Wind, Poweshiek

When: July 21, 3:10 AM CST
Where: Poweshiek County, 0.86 mi SE of Grinnell
Measured: 65 kt (75 mph) estimated gust
Property damage: $50,000
Reported by: Trained Spotter
Coordinates: 41.740, -92.720

Numerous tree limbs down across town and the power was out.

Thunderstorm Wind, Poweshiek

When: July 21, 3:19 AM CST
Where: Poweshiek County, 1.73 mi NW of Montezuma
Measured: 52 kt (60 mph) estimated gust
Property damage: $3,000
Reported by: Trained Spotter
Coordinates: 41.600, -92.550

Thunderstorm Wind, Poweshiek

When: July 21, 3:19 AM CST
Where: Poweshiek County, 0.86 mi NE of Montezuma
Measured: 57 kt (66 mph) measured gust
Property damage: $5,000
Reported by: Mesonet
Coordinates: 41.590, -92.520

Measured gust by KCCI schoolnet site.

Lightning, Poweshiek

When: July 21, 3:19 AM CST
Where: Poweshiek County, Montezuma
Property damage: $10,000
Reported by: Emergency Manager
Coordinates: 41.580, -92.530

Thunderstorm Wind, Poweshiek

When: July 21, 3:24 AM CST
Where: Poweshiek County, 0.52 mi E of Grinnell
Measured: 61 kt (70 mph) estimated gust
Property damage: $15,000
Reported by: Law Enforcement
Coordinates: 41.750, -92.720

Tree damage on the Grinnell College campus.

Thunderstorm Wind, Poweshiek

When: July 21, 3:29 AM CST
Where: Poweshiek County, Deep River
Measured: 57 kt (66 mph) estimated gust
Property damage: $5,000
Reported by: Emergency Manager
Coordinates: 41.580, -92.420

Power lines down.

What these are

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

Every storm in Iowa in 2008 Every state in 2008 This day in weather history Warnings in Iowa, July 2008

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: 104817, 104821, 104917, 104855, 104856, 104916, 104888, 104915, 104853, 104854, 104890, 104956, 104958, 104898, 107147, 104942, 113314, 104951, 104954, 104893, 104897, 104946, 104961, 104869, 104939, 104833, 104857, 104841, 104944, 104918, 104827, 104920, 104830, 104829, 113316, 104924, 104832, 104934, 104858, 104859, and more.