A very intense spring storm system developed over the central Plains and moved east, then northeast across Kansas into eastern Iowa.  The low deepened to 986 mb by 06z of the 11th as it passed over La Crosse, WI.  A southerly low level jet of 40 to 55 kts developed ahead of the storm system.  A warm front extended east from the low and served as a focusing point for thunderstorm development early on, while a dry line extended south from the low lead to the development of a line of severe thunderstorms.  Dew point temperatures in the warm sector soared into the upper 60s to mid 70s with temperature readings in the 80s.  Dew point values at the 850 mb level were in the 14 to 17 degree C. range.  By mid day, CAPE values over eastern KS into western MO were around 5000 J/kg with lifted indices around -11 C.  Thunderstorms developed explosively by the mid afternoon hours.  For the most part, severe weather from the storms in Iowa was in the form of Hail as most of the activity was north of the warm front.  Parts of central into northeast Iowa received golf ball to larger than baseball size hail.  The hardest hit area was in Poweshiek County in the Grinnell area, where 3 inch diameter hail caused considerable damage.  There were scattered reports of nickel to ping pong ball size hail from Interstate 35 east.  A few tornadoes occurred close to the triple point of the storm system.  One tornado touched down in Marion County southwest of Attica and moved into Mahaska County northwest of Leighton.  The track was generally through open countryside with little damage reported.  One trailer was overturned east of Columbia near the beginning of the intermittent track of the tornado.  Another brief touchdown was reported in Tama County near Clutier.  No damage was reported with this tornado.

Hail in DAVIS, IOWA
From 10-MAY-03 16:40:00 to 10-MAY-03 16:40:00 (CST)
Location: PARIS
Magnitude: 1.00 
Property damage: 3K
Reported by: TRAINED SPOTTER

Hail in POWESHIEK, IOWA
From 10-MAY-03 16:40:00 to 10-MAY-03 16:40:00 (CST)
Location: GRINNELL
Magnitude: 1.75 
Property damage: 15K
Reported by: TRAINED SPOTTER

Hail in TAMA, IOWA
From 10-MAY-03 16:06:00 to 10-MAY-03 16:06:00 (CST)
Location: CHELSEA
Magnitude: 1.00 
Property damage: 5K
Reported by: STORM CHASER

Hail in BREMER, IOWA
From 10-MAY-03 17:55:00 to 10-MAY-03 17:55:00 (CST)
Location: READLYN
Magnitude: 0.75 
Reported by: GENERAL PUBLIC

Hail in POWESHIEK, IOWA
From 10-MAY-03 16:45:00 to 10-MAY-03 16:45:00 (CST)
Location: GRINNELL
Magnitude: 2.75 
Property damage: 50K
Reported by: TRAINED SPOTTER

Hail in POWESHIEK, IOWA
From 10-MAY-03 16:47:00 to 10-MAY-03 16:47:00 (CST)
Location: GRINNELL
Magnitude: 1.75 
Property damage: 15K
Reported by: TRAINED SPOTTER

Hail in CERRO GORDO, IOWA
From 10-MAY-03 15:11:00 to 10-MAY-03 15:11:00 (CST)
Location: THORNTON
Magnitude: 1.00 
Property damage: 5K
Reported by: TRAINED SPOTTER

Hail in BLACK HAWK, IOWA
From 10-MAY-03 17:49:00 to 10-MAY-03 17:49:00 (CST)
Location: DUNKERTON
Magnitude: 1.00 
Property damage: 3K
Reported by: TRAINED SPOTTER

Hail in MAHASKA, IOWA
From 10-MAY-03 16:40:00 to 10-MAY-03 16:40:00 (CST)
Location: PEORIA
Magnitude: 2.50 
Property damage: 20K
Reported by: BROADCAST MEDIA

Hail in FRANKLIN, IOWA
From 10-MAY-03 14:52:00 to 10-MAY-03 14:52:00 (CST)
Location: ALEXANDER
Magnitude: 1.00 
Property damage: 3K
Reported by: TRAINED SPOTTER

Hail in POWESHIEK, IOWA
From 10-MAY-03 16:50:00 to 10-MAY-03 16:50:00 (CST)
Location: GRINNELL ARPT
Magnitude: 2.50 
Property damage: 50K
Reported by: BROADCAST MEDIA

Hail in BUTLER, IOWA
From 10-MAY-03 15:44:00 to 10-MAY-03 15:44:00 (CST)
Location: CLARKSVILLE
Magnitude: 0.75 
Reported by: TRAINED SPOTTER

Hail in POWESHIEK, IOWA
From 10-MAY-03 16:40:00 to 10-MAY-03 16:40:00 (CST)
Location: GRINNELL
Magnitude: 2.00 
Property damage: 50K
Reported by: TRAINED SPOTTER

Hail in MARION, IOWA
From 10-MAY-03 16:25:00 to 10-MAY-03 16:25:00 (CST)
Location: PELLA
Magnitude: 1.50 
Property damage: 10K
Reported by: BROADCAST MEDIA

Hail in POWESHIEK, IOWA
From 10-MAY-03 16:50:00 to 10-MAY-03 16:50:00 (CST)
Location: GRINNELL
Magnitude: 3.00 
Property damage: 50K
Reported by: BROADCAST MEDIA

Tornado in MAHASKA, IOWA
From 10-MAY-03 16:55:00 to 10-MAY-03 17:02:00 (CST)
Location: LEIGHTON
Tornado F-scale: F1
Property damage: 2K
Reported by: BROADCAST MEDIA

Moved from Marion County into rural Mahaska County.

Hail in MARION, IOWA
From 10-MAY-03 16:20:00 to 10-MAY-03 16:20:00 (CST)
Location: KNOXVILLE
Magnitude: 1.00 
Property damage: 5K
Reported by: UNKNOWN

Hail in BREMER, IOWA
From 10-MAY-03 18:10:00 to 10-MAY-03 18:10:00 (CST)
Location: WAVERLY
Magnitude: 1.75 
Property damage: 10K
Reported by: BROADCAST MEDIA

Tornado in MARION, IOWA
From 10-MAY-03 16:26:00 to 10-MAY-03 16:55:00 (CST)
Location: COLUMBIA
Tornado F-scale: F1
Property damage: 30K
Reported by: LAW ENFORCEMENT

Moved in rural area northeast into Mahaska County.  Tornado had intermittent track.

Hail in POWESHIEK, IOWA
From 10-MAY-03 16:42:00 to 10-MAY-03 16:42:00 (CST)
Location: GRINNELL
Magnitude: 1.75 
Property damage: 15K
Reported by: TRAINED SPOTTER

Hail in CERRO GORDO, IOWA
From 10-MAY-03 14:54:00 to 10-MAY-03 14:54:00 (CST)
Location: THORNTON
Magnitude: 1.75 
Property damage: 15K
Reported by: BROADCAST MEDIA

Tornado in TAMA, IOWA
From 10-MAY-03 17:27:00 to 10-MAY-03 17:27:00 (CST)
Location: CLUTIER
Tornado F-scale: F0
Reported by: EMERGENCY MANAGER

Brief touchdown in open area.