A cold front moved southeast across the Dakotas into northwest Iowa during the late afternoon and evening hours.  The airmass became quite unstable ahead of the cold front with high temperatures reaching near 90 F. and dew points around 70.  CAPE values were around 4000 J/kg by the late afternoon as lifted indices fell to around -9.  There was a decent amount of CAPE available in the -10 to -30 C. layer of the atmosphere.  I spite of this, very little hail was realized with the freezing level around 16,000 ft.  Shear was fairly weak during the day and increased to around 30 kts during the evening hours.  A narrow line of thunderstorms developed in northwest Iowa during the early evening hours, then drifted south-southeast into west central and central Iowa during the night.  One of the storms produced a brief spin-up tornado in Calhoun County west of Jolley.  The LCL level was relatively high in the area, at around 1500 meters.  That may have limited the lift of the tornado.  It touched down in a field and caused little damage.  Many of the storms produced gusty winds and for a brief period of time the line produced severe winds as they moved into an area of higher DCAPE air with values in the 800 to 1000 J/kg range.  There were scattered reports of crop damage and downed trees as the storms passed.  During the late evening, an area of severe thunderstorms to the northeast of the DMX CWA back developed into northeast Iowa.  One of the storms produced Nickel size hail southeast of Waterloo.

Thunderstorm Wind in BLACK HAWK, IOWA
From 03-JUL-07 22:45:00 to 03-JUL-07 22:45:00 (CST-6)
Location: ORANGE
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in GREENE, IOWA
From 03-JUL-07 21:30:00 to 03-JUL-07 21:30:00 (CST-6)
Location: CHURDAN
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 2.00K
Reported by: Broadcast Media

Thunderstorm Wind in CALHOUN, IOWA
From 03-JUL-07 20:28:00 to 03-JUL-07 20:28:00 (CST-6)
Location: YETTER
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in BLACK HAWK, IOWA
From 03-JUL-07 23:05:00 to 03-JUL-07 23:05:00 (CST-6)
Location: WASHBURN
Magnitude: 0.88 
Property damage: 2.00K
Crop damage: 5.00K
Reported by: Trained Spotter

Tornado in CALHOUN, IOWA
From 03-JUL-07 20:05:00 to 03-JUL-07 20:05:00 (CST-6)
Location: KNOKE
Tornado F-scale: EF0
Property damage: 0.00K
Crop damage: 1.00K
Reported by: Public

Tornado touched down briefly in a field northwest of Jolley.

Thunderstorm Wind in CALHOUN, IOWA
From 03-JUL-07 20:15:00 to 03-JUL-07 20:15:00 (CST-6)
Location: JOLLEY
Magnitude: 57.00 EG
Property damage: 10.00K
Crop damage: 2.00K
Reported by: Broadcast Media

Thunderstorm Wind in CALHOUN, IOWA
From 03-JUL-07 20:22:00 to 03-JUL-07 20:22:00 (CST-6)
Location: LAVINIA
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Thunderstorm Wind in SAC, IOWA
From 03-JUL-07 20:34:00 to 03-JUL-07 20:34:00 (CST-6)
Location: SAC CITY
Magnitude: 52.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in CALHOUN, IOWA
From 03-JUL-07 20:30:00 to 03-JUL-07 20:30:00 (CST-6)
Location: YETTER
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter