An explosive situation became established over Iowa and the central U.S. during the day on the 30th.  A nearly stationary front extended from Wisconsin, southwest through the northwest corner of Iowa, and into northern Kansas.  A round of convection moved across the state during the morning, leaving behind several outflow boundaries.  The mid levels of the atmosphere were quite warm, thus convection was capped during the afternoon hours.  A strong southerly flow of moist air spread into Iowa during the afternoon.  Temperatures approached 100 degrees F. over southwest Iowa.  Dew point temperatures reached the upper 60s to mid 70s across much of the south two thirds of the state.  Thunderstorms developed at the intersection of two outflow boundaries northwest of Des Moines, and also just ahead of the stationary front.  Surface based CAPE values were well over 5000 J/kg, thus the convection developed explosively.  Severe weather quickly followed.  There were numerous reports of hail.  Most of the hail was between one inch in diameter and golf ball size.  One of the cells, which happened to be the initial cell that formed at the boundary intersection, turned into a supercell.  Several tornadoes were spawned by this regenerating cell.  Most of the tornadoes were very weak and short lived.  The exception was one fairly small tornado that touched down on the northeast side of Des Moines.  This tornado tracked through mostly open area and caused little damage on its nearly 10 mile intermittent trek into Altoona.  Gusty winds were reported with many of the cells, however wind speeds were not all that great in most cases.  There was one report of 60 MPH winds as the storms passed through the Saylorville area in Polk County.  Heavy rain fell in a couple parts of the state.  One was with the supercell in Polk County, the other area of heavy rain was in Black Hawk County.  Rainfall amounts in parts of these two counties were in the two to four inch range, however little more than urban and small street flooding occurred due to dry soil conditions.

Tornado in BOONE, IOWA
From 30-MAY-00 18:28:00 to 30-MAY-00 18:28:00 (CST)
Location: BERKLEY
Tornado F-scale: F0
Reported by: BROADCAST MEDIA

Brief touchdown

Hail in BOONE, IOWA
From 30-MAY-00 18:44:00 to 30-MAY-00 18:44:00 (CST)
Location: MADRID
Magnitude: 0.75 
Crop damage: 5K
Reported by: AMATEUR RADIO

Tornado in DALLAS, IOWA
From 30-MAY-00 18:46:00 to 30-MAY-00 18:46:00 (CST)
Location: WOODWARD
Tornado F-scale: F0
Reported by: EMERGENCY MANAGER

Brief touchdown

Tornado in DALLAS, IOWA
From 30-MAY-00 18:59:00 to 30-MAY-00 18:59:00 (CST)
Location: GRANGER
Tornado F-scale: F0
Reported by: EMERGENCY MANAGER

Brief touchdown

Hail in POLK, IOWA
From 30-MAY-00 19:15:00 to 30-MAY-00 19:15:00 (CST)
Location: POLK CITY
Magnitude: 1.75 
Property damage: 25K
Crop damage: 5K
Reported by: NWS EMPLOYEE(OFF DUTY)

Hail in DALLAS, IOWA
From 30-MAY-00 19:30:00 to 30-MAY-00 19:30:00 (CST)
Location: WOODWARD
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in HAMILTON, IOWA
From 30-MAY-00 20:10:00 to 30-MAY-00 20:10:00 (CST)
Location: BLAIRSBURG
Magnitude: 1.00 
Property damage: 5K
Crop damage: 8K
Reported by: TRAINED SPOTTER

Hail in HAMILTON, IOWA
From 30-MAY-00 20:13:00 to 30-MAY-00 20:13:00 (CST)
Location: WILLIAMS
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in HARDIN, IOWA
From 30-MAY-00 20:13:00 to 30-MAY-00 20:13:00 (CST)
Location: BUCKEYE
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in HAMILTON, IOWA
From 30-MAY-00 20:20:00 to 30-MAY-00 20:20:00 (CST)
Location: JEWELL
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in POLK, IOWA
From 30-MAY-00 20:21:00 to 30-MAY-00 20:21:00 (CST)
Location: ANKENY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 3K
Reported by: NWS EMPLOYEE(OFF DUTY)

Hail in POLK, IOWA
From 30-MAY-00 20:25:00 to 30-MAY-00 20:25:00 (CST)
Location: POLK CITY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in POLK, IOWA
From 30-MAY-00 20:27:00 to 30-MAY-00 20:27:00 (CST)
Location: POLK CITY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Flood in POLK, IOWA
From 30-MAY-00 20:28:00 to 30-MAY-00 21:20:00 (CST)
Location: POLK CITY
Property damage: 10K
Reported by: LAW ENFORCEMENT

Hail in HAMILTON, IOWA
From 30-MAY-00 20:30:00 to 30-MAY-00 20:30:00 (CST)
Location: WILLIAMS
Magnitude: 1.75 
Property damage: 25K
Crop damage: 10K
Reported by: TRAINED SPOTTER

Tornado in POLK, IOWA
From 30-MAY-00 20:35:00 to 30-MAY-00 20:47:00 (CST)
Location: DES MOINES
Tornado F-scale: F1
Property damage: 100K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Intermittent path

Thunderstorm Wind in POLK, IOWA
From 30-MAY-00 20:40:00 to 30-MAY-00 20:40:00 (CST)
Location: SAYLORVILLE
Magnitude: 52 E
Property damage: 3K
Reported by: LAW ENFORCEMENT

Hail in BLACK HAWK, IOWA
From 30-MAY-00 19:31:00 to 30-MAY-00 19:31:00 (CST)
Location: CEDAR FALLS
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in BLACK HAWK, IOWA
From 30-MAY-00 19:33:00 to 30-MAY-00 19:33:00 (CST)
Location: CEDAR FALLS
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Flood in BLACK HAWK, IOWA
From 30-MAY-00 19:33:00 to 30-MAY-00 20:30:00 (CST)
Location: WATERLOO
Property damage: 10K
Reported by: EMERGENCY MANAGER

Hail in POLK, IOWA
From 30-MAY-00 19:35:00 to 30-MAY-00 19:35:00 (CST)
Location: ANKENY
Magnitude: 1.00 
Property damage: 15K
Crop damage: 3K
Reported by: NWS EMPLOYEE(OFF DUTY)

Hail in BLACK HAWK, IOWA
From 30-MAY-00 19:42:00 to 30-MAY-00 19:42:00 (CST)
Location: CEDAR FALLS
Magnitude: 1.50 
Property damage: 25K
Crop damage: 5K
Reported by: BROADCAST MEDIA

Hail in BLACK HAWK, IOWA
From 30-MAY-00 19:43:00 to 30-MAY-00 19:43:00 (CST)
Location: CEDAR FALLS
Magnitude: 1.00 
Property damage: 5K
Crop damage: 2K
Reported by: EMERGENCY MANAGER

Hail in DALLAS, IOWA
From 30-MAY-00 19:54:00 to 30-MAY-00 19:54:00 (CST)
Location: WOODWARD
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: EMERGENCY MANAGER

Hail in JASPER, IOWA
From 30-MAY-00 23:10:00 to 30-MAY-00 23:10:00 (CST)
Location: GALESBURG
Magnitude: 0.88 
Property damage: 2K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in GRUNDY, IOWA
From 30-MAY-00 23:27:00 to 30-MAY-00 23:27:00 (CST)
Location: HOLLAND
Magnitude: 0.75 
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in POLK, IOWA
From 30-MAY-00 19:10:00 to 30-MAY-00 19:10:00 (CST)
Location: POLK CITY
Magnitude: 1.00 
Property damage: 3K
Crop damage: 3K
Reported by: AMATEUR RADIO

Hail in POLK, IOWA
From 30-MAY-00 19:20:00 to 30-MAY-00 19:20:00 (CST)
Location: ANKENY
Magnitude: 1.00 
Property damage: 3K
Crop damage: 5K
Reported by: AMATEUR RADIO

Hail in POLK, IOWA
From 30-MAY-00 19:47:00 to 30-MAY-00 19:47:00 (CST)
Location: ANKENY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 3K
Reported by: AMATEUR RADIO

Hail in JASPER, IOWA
From 30-MAY-00 21:44:00 to 30-MAY-00 21:44:00 (CST)
Location: NEWTON
Magnitude: 0.88 
Property damage: 3K
Crop damage: 5K
Reported by: AMATEUR RADIO

Hail in JASPER, IOWA
From 30-MAY-00 22:00:00 to 30-MAY-00 22:00:00 (CST)
Location: KELLOGG
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: AMATEUR RADIO

Hail in POLK, IOWA
From 30-MAY-00 19:15:00 to 30-MAY-00 19:15:00 (CST)
Location: POLK CITY
Magnitude: 1.00 
Property damage: 1K
Crop damage: 2K
Reported by: STORM CHASER

Hail in POLK, IOWA
From 30-MAY-00 20:49:00 to 30-MAY-00 20:49:00 (CST)
Location: DES MOINES
Magnitude: 1.00 
Property damage: 5K
Crop damage: 2K
Reported by: TRAINED SPOTTER

Hail in STORY, IOWA
From 30-MAY-00 20:49:00 to 30-MAY-00 20:49:00 (CST)
Location: AMES
Magnitude: 0.88 
Property damage: 3K
Crop damage: 3K
Reported by: TRAINED SPOTTER

Tornado in POLK, IOWA
From 30-MAY-00 21:00:00 to 30-MAY-00 21:00:00 (CST)
Location: DES MOINES
Tornado F-scale: F0
Reported by: TRAINED SPOTTER

Brief touchdown

Hail in POLK, IOWA
From 30-MAY-00 21:05:00 to 30-MAY-00 21:05:00 (CST)
Location: POLK CITY
Magnitude: 1.00 
Property damage: 5K
Crop damage: 5K
Reported by: TRAINED SPOTTER

Hail in JASPER, IOWA
From 30-MAY-00 20:48:00 to 30-MAY-00 20:48:00 (CST)
Location: NEWTON
Magnitude: 0.88 
Property damage: 2K
Crop damage: 3K
Reported by: LAW ENFORCEMENT

Hail in JASPER, IOWA
From 30-MAY-00 20:50:00 to 30-MAY-00 20:50:00 (CST)
Location: NEWTON
Magnitude: 1.50 
Property damage: 8K
Crop damage: 5K
Reported by: LAW ENFORCEMENT

Hail in GRUNDY, IOWA
From 30-MAY-00 22:05:00 to 30-MAY-00 22:05:00 (CST)
Location: GRUNDY CENTER
Magnitude: 1.75 
Property damage: 8K
Crop damage: 5K
Reported by: TRAINED SPOTTER