A very unstable airmass was over Iowa and helped kick off the seasons first severe weather outbreak.  At the surface a warm frontal boundary extended nearly east to west across the state and provided the focus for thunderstorm development.  By the late afternoon, lifted indices were approaching -10 C. with CAPE values around 5000 J/kg over western Iowa.  Surface temperatures warmed into the upper 80s with dew points in the low to mid 70s.  A southwest surface wind of 15 to 25 kts pushed over the front.  Northeast of the frontal boundary winds were easterly around 10 to 15 kts.  Actually, the surface boundary was further enhanced by outflow from convective complexes during the day, further sharpening the contrast.  Thunderstorms continued to fire along and north of the boundary through the afternoon and into the evening.  This resulted in widespread flash flooding as very heavy rains fell on areas that had had significant rainfall the previous night.  There were reports in north central into northeast Iowa of 2 to 4 inches of rainfall in a little more than an hours time.  Major flooding took place in the Mason City area where evacuations were taking place.  The thunderstorms became most intense during the afternoon into the early evening.  There were several tornadoes across northeast into north central Iowa.  Most were relatively brief touchdowns and were in open areas.  Reports of multi-vortex tornadoes were received from Grundy County.  The days most significant tornado touched down in Pocahontas County east of Rolfe and tracked into Humboldt County through the Bradgate area.  The tornado damaged or destroyed over 75% of the town of Bradgate (pop 120).  Tornado damage in Bradgate was very extensive impacting most of the town.  Hardly a building was not impacted.   Outbuildings, light structures and garages were heavily damaged or destroyed.  Two homes were destroyed.  Several homes were damaged ranging from minor to extensive.  The Survey Team found that the majority of the damage was F1, with a few cases of F2 damage.  The F2 damage was to the snapping of very large trees just west of town and the structural damage to two buildings.  Nearly all of the 53 homes there reported damage with several totally destroyed.  Significant widespread property damage was reported in the tornadoes path.  There were several injuries in the town, the most significant being a broken leg.  A police officer was reportedly hit by debris from the tornado and suffered a broken leg.  According to law officials, the damage path of the tornado was 2 miles wide and about 8 miles long.  Storm chasers on the scene reported the tornado itself to be one half mile wide at one point.  Reports of hail were numerous through the afternoon and evening.  Most of the hail was in the three quarter inch to one inch diameter range.  There were a few reports of golf ball size hail from the stronger storms.  Winds were not a major problem with the activity.  There were spotty reports of winds to around 60 MPH, but most reports were in the 40 to 50 MPH range.  One of the stronger wind reports was a 64 MPH wind gust in Tripoli in Bremer County.  This gust was measured by a mesonet station there.  During the mid evening hours, thunderstorms rumbled across Grundy County.  Lightning struck the Sheriff's office there and destroyed a significant amount of office equipment.  Damage was reported around $100,000.

Hail in HANCOCK, IOWA
From 21-MAY-04 10:15:00 to 21-MAY-04 10:15:00 (CST)
Location: BRITT
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: GENERAL PUBLIC

Hail in WORTH, IOWA
From 21-MAY-04 10:25:00 to 21-MAY-04 10:25:00 (CST)
Location: NORTHWOOD
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in HANCOCK, IOWA
From 21-MAY-04 10:25:00 to 21-MAY-04 10:25:00 (CST)
Location: BRITT
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in PALO ALTO, IOWA
From 21-MAY-04 10:30:00 to 21-MAY-04 10:30:00 (CST)
Location: RUTHVEN
Magnitude: 1.75 
Property damage: 5K
Crop damage: 5K
Reported by: BROADCAST MEDIA

Hail in WRIGHT, IOWA
From 21-MAY-04 18:35:00 to 21-MAY-04 18:35:00 (CST)
Location: CLARION
Magnitude: 0.88 
Property damage: 1K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in BREMER, IOWA
From 22-MAY-04 00:44:00 to 22-MAY-04 00:44:00 (CST)
Location: TRIPOLI
Magnitude: 56 MG
Property damage: 5K
Reported by: AWOS,ASOS,MESONET,ETC

Thunderstorm Wind in CASS, IOWA
From 22-MAY-04 04:08:00 to 22-MAY-04 04:08:00 (CST)
Location: ATLANTIC
Magnitude: 52 MG
Property damage: 2K
Reported by: AWOS,ASOS,MESONET,ETC

Hail in HARDIN, IOWA
From 21-MAY-04 13:30:00 to 21-MAY-04 13:30:00 (CST)
Location: ALDEN
Magnitude: 1.75 
Property damage: 10K
Crop damage: 5K
Reported by: NEWSPAPER

Hail in FRANKLIN, IOWA
From 21-MAY-04 13:31:00 to 21-MAY-04 13:31:00 (CST)
Location: POPEJOY
Magnitude: 0.88 
Property damage: 1K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Flash Flood in CERRO GORDO, IOWA
From 21-MAY-04 18:26:00 to 21-MAY-04 23:15:00 (CST)
Location: COUNTYWIDE
Property damage: 100K
Crop damage: 50K
Reported by: AMATEUR RADIO

Tornado in WRIGHT, IOWA
From 21-MAY-04 18:30:00 to 21-MAY-04 18:30:00 (CST)
Location: CLARION
Tornado F-scale: F0
Reported by: GENERAL PUBLIC

Brief touchdown in open area northwest of Clarion.

Thunderstorm Wind in WRIGHT, IOWA
From 21-MAY-04 18:30:00 to 21-MAY-04 18:30:00 (CST)
Location: CLARION
Magnitude: 52 EG
Property damage: 2K
Reported by: LAW ENFORCEMENT

Flash Flood in HANCOCK, IOWA
From 21-MAY-04 18:33:00 to 21-MAY-04 23:15:00 (CST)
Location: COUNTYWIDE
Property damage: 100K
Crop damage: 50K
Reported by: AMATEUR RADIO

Hail in HARDIN, IOWA
From 21-MAY-04 14:00:00 to 21-MAY-04 14:00:00 (CST)
Location: ALDEN
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in GRUNDY, IOWA
From 21-MAY-04 14:06:00 to 21-MAY-04 14:06:00 (CST)
Location: GRUNDY CENTER
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Tornado in GRUNDY, IOWA
From 21-MAY-04 14:15:00 to 21-MAY-04 14:15:00 (CST)
Location: GRUNDY CENTER
Tornado F-scale: F0
Reported by: AMATEUR RADIO

Tornado touched down in open areas west of Grundy Center and crossed Highway 175.

Hail in TAMA, IOWA
From 21-MAY-04 14:15:00 to 21-MAY-04 14:15:00 (CST)
Location: TRAER
Magnitude: 1.25 
Property damage: 5K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in GRUNDY, IOWA
From 21-MAY-04 14:17:00 to 21-MAY-04 14:17:00 (CST)
Location: DIKE
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in BLACK HAWK, IOWA
From 21-MAY-04 14:21:00 to 21-MAY-04 14:21:00 (CST)
Location: WATERLOO
Magnitude: 1.00 
Property damage: 5K
Crop damage: 2K
Reported by: TRAINED SPOTTER

Tornado in BLACK HAWK, IOWA
From 21-MAY-04 14:21:00 to 21-MAY-04 14:21:00 (CST)
Location: WATERLOO
Tornado F-scale: F0
Reported by: GENERAL PUBLIC

Brief touchdown in open areas south of Waterloo.

Tornado in GRUNDY, IOWA
From 21-MAY-04 14:22:00 to 21-MAY-04 14:22:00 (CST)
Location: GRUNDY CENTER
Tornado F-scale: F0
Reported by: AMATEUR RADIO

Tornado touched down in open fields northwest of Grundy Center.

Flash Flood in CERRO GORDO, IOWA
From 21-MAY-04 19:03:00 to 21-MAY-04 23:15:00 (CST)
Location: COUNTYWIDE
Property damage: 150K
Crop damage: 50K
Reported by: LAW ENFORCEMENT

Flash Flood in BUTLER, IOWA
From 21-MAY-04 19:15:00 to 21-MAY-04 23:15:00 (CST)
Location: COUNTYWIDE
Property damage: 100K
Crop damage: 50K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in BREMER, IOWA
From 21-MAY-04 19:19:00 to 21-MAY-04 19:19:00 (CST)
Location: WAVERLY
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Hail in BLACK HAWK, IOWA
From 21-MAY-04 14:45:00 to 21-MAY-04 14:45:00 (CST)
Location: RAYMOND
Magnitude: 0.88 
Property damage: 1K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in BLACK HAWK, IOWA
From 21-MAY-04 15:04:00 to 21-MAY-04 15:04:00 (CST)
Location: WATERLOO
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Thunderstorm Wind in TAMA, IOWA
From 21-MAY-04 15:10:00 to 21-MAY-04 15:10:00 (CST)
Location: TRAER
Magnitude: 57 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Hail in TAMA, IOWA
From 21-MAY-04 15:16:00 to 21-MAY-04 15:16:00 (CST)
Location: TRAER
Magnitude: 1.00 
Property damage: 5K
Crop damage: 3K
Reported by: TRAINED SPOTTER

Hail in TAMA, IOWA
From 21-MAY-04 15:20:00 to 21-MAY-04 15:20:00 (CST)
Location: DYSART
Magnitude: 0.88 
Property damage: 1K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in TAMA, IOWA
From 21-MAY-04 15:23:00 to 21-MAY-04 15:23:00 (CST)
Location: CLUTIER
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Hail in CERRO GORDO, IOWA
From 21-MAY-04 16:39:00 to 21-MAY-04 16:39:00 (CST)
Location: MESERVEY
Magnitude: 1.00 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in CERRO GORDO, IOWA
From 21-MAY-04 16:55:00 to 21-MAY-04 16:55:00 (CST)
Location: CLEAR LAKE
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: NWS EMPLOYEE(OFF DUTY)

Thunderstorm Wind in BREMER, IOWA
From 21-MAY-04 19:50:00 to 21-MAY-04 19:50:00 (CST)
Location: READLYN
Magnitude: 52 EG
Property damage: 2K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in BREMER, IOWA
From 21-MAY-04 20:43:00 to 21-MAY-04 20:43:00 (CST)
Location: WAVERLY
Magnitude: 61 EG
Property damage: 10K
Reported by: EMERGENCY MANAGER

Hail in PALO ALTO, IOWA
From 21-MAY-04 21:59:00 to 21-MAY-04 21:59:00 (CST)
Location: MALLARD
Magnitude: 0.75 
Crop damage: 5K
Reported by: BROADCAST MEDIA

Hail in WORTH, IOWA
From 21-MAY-04 22:02:00 to 21-MAY-04 22:02:00 (CST)
Location: MANLY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: BROADCAST MEDIA

Flash Flood in WORTH, IOWA
From 21-MAY-04 23:20:00 to 22-MAY-04 03:00:00 (CST)
Location: COUNTYWIDE
Property damage: 100K
Crop damage: 50K
Reported by: LAW ENFORCEMENT

Flash Flood in WRIGHT, IOWA
From 21-MAY-04 23:35:00 to 22-MAY-04 03:00:00 (CST)
Location: EAGLE GROVE
Property damage: 50K
Crop damage: 20K
Reported by: BROADCAST MEDIA

Tornado in GRUNDY, IOWA
From 21-MAY-04 13:49:00 to 21-MAY-04 13:49:00 (CST)
Location: DIKE
Tornado F-scale: F0
Reported by: TRAINED SPOTTER

Tornado touched down in farm fields southwest of Dike.

Hail in HARDIN, IOWA
From 21-MAY-04 13:50:00 to 21-MAY-04 13:50:00 (CST)
Location: ALDEN
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in GRUNDY, IOWA
From 21-MAY-04 13:53:00 to 21-MAY-04 13:53:00 (CST)
Location: DIKE
Magnitude: 1.75 
Property damage: 5K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in FRANKLIN, IOWA
From 21-MAY-04 13:53:00 to 21-MAY-04 13:53:00 (CST)
Location: POPEJOY
Magnitude: 57 EG
Property damage: 10K
Reported by: GENERAL PUBLIC

Tornado in POCAHONTAS, IOWA
From 21-MAY-04 17:00:00 to 21-MAY-04 17:11:00 (CST)
Location: ROLFE
Tornado F-scale: F1
Property damage: 25K
Crop damage: 2K
Reported by: NWS STORM SURVEY

Tornado tracked southeast in open fields, just missing the town of Rolfe.

Hail in GRUNDY, IOWA
From 21-MAY-04 13:15:00 to 21-MAY-04 13:25:00 (CST)
Location: GRUNDY CENTER
Magnitude: 1.00 
Property damage: 2K
Crop damage: 5K
Reported by: STORM CHASER

Lightning in GRUNDY, IOWA
From 21-MAY-04 19:00:00 to 21-MAY-04 19:00:00 (CST)
Location: GRUNDY CENTER
Property damage: 100K
Reported by: NEWSPAPER

Hail in HARDIN, IOWA
From 21-MAY-04 13:40:00 to 21-MAY-04 13:40:00 (CST)
Location: IOWA FALLS
Magnitude: 1.75 
Property damage: 20K
Crop damage: 5K
Reported by: NEWSPAPER

Thunderstorm Wind in CALHOUN, IOWA
From 22-MAY-04 00:00:00 to 22-MAY-04 00:00:00 (CST)
Location: MANSON
Magnitude: 52 EG
Property damage: 5K
Reported by: NEWSPAPER

Tornado in GRUNDY, IOWA
From 21-MAY-04 13:38:00 to 21-MAY-04 13:42:00 (CST)
Location: GRUNDY CENTER
Tornado F-scale: F1
Property damage: 2K
Crop damage: 3K
Reported by: LAW ENFORCEMENT

Tornado touched down in open fields.  Dust debris blown across highway 14 as it crossed.  The track was intermittent and the tornado was reported to be multiple vortex at times with two tornadoes on the ground at one point northeast of Grundy Center.

Hail in GRUNDY, IOWA
From 21-MAY-04 13:42:00 to 21-MAY-04 13:42:00 (CST)
Location: DIKE
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: AMATEUR RADIO

Thunderstorm Wind in WRIGHT, IOWA
From 21-MAY-04 19:05:00 to 21-MAY-04 19:05:00 (CST)
Location: DOWS
Magnitude: 57 EG
Property damage: 10K
Reported by: EMERGENCY MANAGER

Hail in PALO ALTO, IOWA
From 21-MAY-04 10:31:00 to 21-MAY-04 10:31:00 (CST)
Location: RUTHVEN
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in WORTH, IOWA
From 21-MAY-04 10:40:00 to 21-MAY-04 10:40:00 (CST)
Location: NORTHWOOD
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in BUTLER, IOWA
From 21-MAY-04 11:35:00 to 21-MAY-04 11:35:00 (CST)
Location: GREENE
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in HARDIN, IOWA
From 21-MAY-04 12:52:00 to 21-MAY-04 12:52:00 (CST)
Location: STEAMBOAT ROCK
Magnitude: 0.88 
Property damage: 3K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in HAMILTON, IOWA
From 21-MAY-04 13:20:00 to 21-MAY-04 13:20:00 (CST)
Location: WEBSTER CITY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 3K
Reported by: TRAINED SPOTTER

Hail in FRANKLIN, IOWA
From 21-MAY-04 13:21:00 to 21-MAY-04 13:21:00 (CST)
Location: DOWS
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER

Tornado in GRUNDY, IOWA
From 21-MAY-04 13:28:00 to 21-MAY-04 13:32:00 (CST)
Location: HOLLAND
Tornado F-scale: F0
Reported by: LAW ENFORCEMENT

Several brief touchdowns in open fields around the Holland area.  Track was very intermittent.

Hail in BLACK HAWK, IOWA
From 21-MAY-04 14:30:00 to 21-MAY-04 14:30:00 (CST)
Location: WATERLOO
Magnitude: 1.75 
Property damage: 10K
Crop damage: 2K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in BLACK HAWK, IOWA
From 21-MAY-04 14:33:00 to 21-MAY-04 14:33:00 (CST)
Location: CEDAR FALLS
Magnitude: 52 EG
Property damage: 2K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in BLACK HAWK, IOWA
From 21-MAY-04 14:35:00 to 21-MAY-04 14:35:00 (CST)
Location: EVANSDALE
Magnitude: 52 EG
Property damage: 4K
Reported by: AMATEUR RADIO

Hail in BLACK HAWK, IOWA
From 21-MAY-04 14:41:00 to 21-MAY-04 14:41:00 (CST)
Location: WATERLOO
Magnitude: 0.88 
Property damage: 2K
Crop damage: 2K
Reported by: LAW ENFORCEMENT

Hail in GRUNDY, IOWA
From 21-MAY-04 14:42:00 to 21-MAY-04 14:42:00 (CST)
Location: GRUNDY CENTER
Magnitude: 1.75 
Property damage: 10K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in GRUNDY, IOWA
From 21-MAY-04 17:00:00 to 21-MAY-04 17:00:00 (CST)
Location: GRUNDY CENTER
Magnitude: 0.75 
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in GRUNDY, IOWA
From 21-MAY-04 17:02:00 to 21-MAY-04 17:02:00 (CST)
Location: GRUNDY CENTER
Magnitude: 1.75 
Property damage: 10K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in CERRO GORDO, IOWA
From 21-MAY-04 17:02:00 to 21-MAY-04 17:02:00 (CST)
Location: CLEAR LAKE
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in CERRO GORDO, IOWA
From 21-MAY-04 17:07:00 to 21-MAY-04 17:07:00 (CST)
Location: MESERVEY
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in BREMER, IOWA
From 21-MAY-04 18:09:00 to 21-MAY-04 18:09:00 (CST)
Location: PLAINFIELD
Magnitude: 1.00 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Tornado in POCAHONTAS, IOWA
From 21-MAY-04 17:08:00 to 21-MAY-04 17:19:00 (CST)
Location: ROLFE
Tornado F-scale: F2
Property damage: 25K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Tornado touched down in open areas east of Rolfe.  It did some damage but didn't do significant damage before crossing into Humboldt County.

Tornado in HUMBOLDT, IOWA
From 21-MAY-04 17:19:00 to 21-MAY-04 17:35:00 (CST)
Location: BRADGATE
Tornado F-scale: F2
Property damage: 2.5M
Crop damage: 10K
Reported by: BROADCAST MEDIA

Tornado intensified as it approached Bradgate.  Seventy five percent of the town was damaged or destroyed by the tornado which was one half mile wide as it moved through.

Flash Flood in KOSSUTH, IOWA
From 21-MAY-04 17:00:00 to 22-MAY-04 03:00:00 (CST)
Location: SOUTH PORTION
Property damage: 100K
Crop damage: 50K
Reported by: EMERGENCY MANAGER

Hail in KOSSUTH, IOWA
From 21-MAY-04 17:40:00 to 21-MAY-04 17:40:00 (CST)
Location: ALGONA
Magnitude: 1.00 
Property damage: 1K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in POCAHONTAS, IOWA
From 21-MAY-04 17:46:00 to 21-MAY-04 17:46:00 (CST)
Location: ROLFE
Magnitude: 0.75 
Crop damage: 5K
Reported by: STORM CHASER

Hail in BUTLER, IOWA
From 21-MAY-04 17:52:00 to 21-MAY-04 17:52:00 (CST)
Location: NEW HARTFORD
Magnitude: 1.00 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in HUMBOLDT, IOWA
From 21-MAY-04 17:55:00 to 21-MAY-04 17:55:00 (CST)
Location: RENWICK
Magnitude: 1.00 
Property damage: 2K
Crop damage: 5K
Reported by: STORM CHASER

Hail in HANCOCK, IOWA
From 21-MAY-04 18:12:00 to 21-MAY-04 18:12:00 (CST)
Location: KANAWHA
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Thunderstorm Wind in BREMER, IOWA
From 21-MAY-04 19:23:00 to 21-MAY-04 19:23:00 (CST)
Location: WAVERLY
Magnitude: 52 EG
Property damage: 5K
Reported by: TRAINED SPOTTER

Flash Flood in BREMER, IOWA
From 21-MAY-04 19:35:00 to 21-MAY-04 23:15:00 (CST)
Location: COUNTYWIDE
Property damage: 100K
Crop damage: 50K
Reported by: TRAINED SPOTTER

Hail in BLACK HAWK, IOWA
From 21-MAY-04 14:45:00 to 21-MAY-04 14:45:00 (CST)
Location: WATERLOO
Magnitude: 0.88 
Property damage: 1K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in BREMER, IOWA
From 21-MAY-04 17:57:00 to 21-MAY-04 17:57:00 (CST)
Location: PLAINFIELD
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: TRAINED SPOTTER