A southerly flow of moist and unstable air moved into Iowa during the afternoon of the 9th.  A cold front was positioned to the northwest of the state and began moving southeast across South Dakota.  As the cold front advanced southeast, thunderstorms erupted over northwest Iowa.  As the evening progressed, the storms worked toward the southeast.  Most of the severe weather associated with the storms was in the form of hail with only scattered reports of high winds.  Hail of three quarter inch to a little over an inch in diameter was common.  A few reports of golf ball size hail were received.  In Pocahontas County, golf ball size hail pelted the town of Havelock.  Later in the evening, golf ball size hail was reported in Tama County in the town of Gladbrook.  There were only a couple areas where significant wind damage was reported.  In the Atlantic area of Cass County, winds around 70 MPH caused damage with numerous reports of trees down in the area.  In Guthrie County, high winds toppled several trees in the Yale area.  One of the trees fell into some power lines, knocking out power for a portion of eastern Guthrie County.

Hail in POCAHONTAS, IOWA
From 09-MAY-01 18:33:00 to 09-MAY-01 18:33:00 (CST)
Location: LAURENS
Magnitude: 1.00 
Property damage: 5K
Reported by: LAW ENFORCEMENT

Hail in CASS, IOWA
From 09-MAY-01 23:19:00 to 09-MAY-01 23:19:00 (CST)
Location: GRISWOLD
Magnitude: 1.00 
Property damage: 5K
Reported by: TRAINED SPOTTER

Hail in GRUNDY, IOWA
From 09-MAY-01 21:29:00 to 09-MAY-01 21:29:00 (CST)
Location: CONRAD
Magnitude: 1.00 
Property damage: 5K
Reported by: BROADCAST MEDIA

Hail in CASS, IOWA
From 09-MAY-01 21:33:00 to 09-MAY-01 21:33:00 (CST)
Location: ATLANTIC
Magnitude: 0.75 
Property damage: 1K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in CASS, IOWA
From 09-MAY-01 21:37:00 to 09-MAY-01 21:37:00 (CST)
Location: ATLANTIC
Magnitude: 61 E
Property damage: 10K
Reported by: LAW ENFORCEMENT

Hail in POCAHONTAS, IOWA
From 09-MAY-01 18:57:00 to 09-MAY-01 18:57:00 (CST)
Location: HAVELOCK
Magnitude: 1.00 
Property damage: 5K
Reported by: TRAINED SPOTTER

Hail in CASS, IOWA
From 09-MAY-01 21:37:00 to 09-MAY-01 21:37:00 (CST)
Location: ATLANTIC
Magnitude: 0.75 
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in GUTHRIE, IOWA
From 09-MAY-01 20:15:00 to 09-MAY-01 20:15:00 (CST)
Location: YALE
Magnitude: 56 E
Property damage: 10K
Reported by: LAW ENFORCEMENT

Hail in PALO ALTO, IOWA
From 09-MAY-01 18:54:00 to 09-MAY-01 18:54:00 (CST)
Location: CURLEW
Magnitude: 1.00 
Property damage: 3K
Reported by: BROADCAST MEDIA

Hail in HAMILTON, IOWA
From 09-MAY-01 20:25:00 to 09-MAY-01 20:25:00 (CST)
Location: WEBSTER CITY
Magnitude: 1.00 
Property damage: 10K
Reported by: LAW ENFORCEMENT

Thunderstorm Wind in CASS, IOWA
From 09-MAY-01 21:45:00 to 09-MAY-01 21:45:00 (CST)
Location: ATLANTIC
Magnitude: 56 E
Property damage: 15K
Reported by: LAW ENFORCEMENT

Hail in SAC, IOWA
From 09-MAY-01 18:15:00 to 09-MAY-01 18:15:00 (CST)
Location: ODEBOLT
Magnitude: 0.88 
Property damage: 2K
Reported by: EMERGENCY MANAGER

Thunderstorm Wind in WEBSTER, IOWA
From 09-MAY-01 19:50:00 to 09-MAY-01 19:50:00 (CST)
Location: LEHIGH
Magnitude: 61 E
Property damage: 10K
Reported by: BROADCAST MEDIA

Hail in TAMA, IOWA
From 09-MAY-01 21:55:00 to 09-MAY-01 21:55:00 (CST)
Location: GLADBROOK
Magnitude: 1.75 
Property damage: 25K
Reported by: LAW ENFORCEMENT

Hail in CERRO GORDO, IOWA
From 09-MAY-01 20:30:00 to 09-MAY-01 20:30:00 (CST)
Location: MASON CITY
Magnitude: 0.88 
Property damage: 5K
Reported by: AMATEUR RADIO

Hail in MARSHALL, IOWA
From 09-MAY-01 21:29:00 to 09-MAY-01 21:29:00 (CST)
Location: LISCOMB
Magnitude: 1.00 
Property damage: 5K
Reported by: BROADCAST MEDIA

Thunderstorm Wind in CASS, IOWA
From 09-MAY-01 23:19:00 to 09-MAY-01 23:19:00 (CST)
Location: GRISWOLD
Magnitude: 61 E
Property damage: 10K
Reported by: TRAINED SPOTTER

Hail in AUDUBON, IOWA
From 09-MAY-01 19:43:00 to 09-MAY-01 19:43:00 (CST)
Location: AUDUBON
Magnitude: 0.88 
Property damage: 5K
Reported by: TRAINED SPOTTER

Hail in POCAHONTAS, IOWA
From 09-MAY-01 18:35:00 to 09-MAY-01 18:35:00 (CST)
Location: LAURENS
Magnitude: 1.00 
Property damage: 3K
Reported by: TRAINED SPOTTER

Hail in POCAHONTAS, IOWA
From 09-MAY-01 19:00:00 to 09-MAY-01 19:00:00 (CST)
Location: HAVELOCK
Magnitude: 1.75 
Property damage: 20K
Reported by: TRAINED SPOTTER