A broad southwesterly flow was in place over Iowa as low pressure developed over the High Plains.  Strong theta-e advection took place over the CWA overnight and into the morning hours.  South winds of 50 kts at 925 mb to the southwest of Iowa pushed into 35 kt winds over Iowa, while at 850 mb 45 kt winds to the southwest of Iowa converged into 30 kt winds over Iowa.  Thunderstorms developed early in the morning with the environment favorable for elevated convection.  Surface based lifted indices were in the +2 to +6 C. range, however the Showalter indices were in the -4 to -6 C. range.  Zero to 6 km shear was in the 30-40 kt range with most unstable CAPE between 500 and 1500 J/kg.  CAPE in the -10 to -30 layer was quite high, in the 200 to 400 J/kg range.  Freezing levels were in the 11,000 to 12,000 foot range.  Many of the thunderstorms produced hail.  They became severe as the approached central Iowa and produced hail up to golf ball size in the Des Moines area.  A cluster of severe thunderstorms continued across central Iowa and advanced into Marshall and Story Counties before weakening around mid day.

Hail in MADISON, IOWA
From 21-MAR-07 07:44:00 to 21-MAR-07 07:44:00 (CST-6)
Location: EARLHAM
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in DALLAS, IOWA
From 21-MAR-07 08:10:00 to 21-MAR-07 08:10:00 (CST-6)
Location: WAUKEE
Magnitude: 1.75 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in POLK, IOWA
From 21-MAR-07 08:14:00 to 21-MAR-07 08:14:00 (CST-6)
Location: URBANDALE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Hail in POLK, IOWA
From 21-MAR-07 08:18:00 to 21-MAR-07 08:18:00 (CST-6)
Location: URBANDALE
Magnitude: 0.88 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: NWS Employee

Hail in POLK, IOWA
From 21-MAR-07 08:10:00 to 21-MAR-07 08:10:00 (CST-6)
Location: WEST DES MOINES
Magnitude: 0.88 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Hail in POLK, IOWA
From 21-MAR-07 08:25:00 to 21-MAR-07 08:25:00 (CST-6)
Location: JOHNSTON
Magnitude: 0.88 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DALLAS, IOWA
From 21-MAR-07 09:16:00 to 21-MAR-07 09:16:00 (CST-6)
Location: GRANGER
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Hail in MARSHALL, IOWA
From 21-MAR-07 10:31:00 to 21-MAR-07 10:31:00 (CST-6)
Location: MARSHALLTOWN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 21-MAR-07 09:35:00 to 21-MAR-07 09:35:00 (CST-6)
Location: POLK CITY
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 21-MAR-07 08:10:00 to 21-MAR-07 08:10:00 (CST-6)
Location: WEST DES MOINES
Magnitude: 1.00 
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in DALLAS, IOWA
From 21-MAR-07 08:05:00 to 21-MAR-07 08:10:00 (CST-6)
Location: WAUKEE
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 21-MAR-07 08:15:00 to 21-MAR-07 08:15:00 (CST-6)
Location: WEST DES MOINES
Magnitude: 0.88 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POLK, IOWA
From 21-MAR-07 08:26:00 to 21-MAR-07 08:26:00 (CST-6)
Location: JOHNSTON
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: County Official

Reported by Johnston City Official.

Hail in JASPER, IOWA
From 21-MAR-07 09:05:00 to 21-MAR-07 09:05:00 (CST-6)
Location: MINGO
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in STORY, IOWA
From 21-MAR-07 09:25:00 to 21-MAR-07 09:25:00 (CST-6)
Location: HUXLEY
Magnitude: 1.00 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: County Official

Hail in MARSHALL, IOWA
From 21-MAR-07 10:49:00 to 21-MAR-07 10:49:00 (CST-6)
Location: ALBION
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter