An unstable airmass was in place over central Iowa ahead of an approaching cold front.  CAPE increased to 2000 to 3000 J/kg with downdraft CAPE around 1200 J/kg.  The available CAPE in the -10 to -30 C layer of the atmosphere was in the 400 to 600 J/kg range.  Though the freezing level was quite high around 15,000 feet, the atmosphere was moderately sheared with 35 to 45 kts of effective shear.  Precipitable water was around 1.6 inches.  During the afternoon, highs reached the low 90s with dewpoint readings around 70.  Thunderstorms developed over central Iowa and dropped hail up to 2.5 inches diameter in Jasper County.  The first round of thunderstorms weakened with sub-severe storms continuing.  During the evening thunderstorms intensified again as the low level jet increased.  The storms produced spotty hail, high winds, and local heavy rainfall.

Thunderstorm Wind in ADAMS, IOWA
From 07-AUG-13 00:20:00 to 07-AUG-13 00:20:00 (CST-6)
Location: MERCER
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 25.00K
Reported by: Trained Spotter

Two foot diameter tree snapped.  One to 1.5 inch diameter flagpole bent southwest approximately 30 degrees along Highway 34.  Winds estimated at 70 MPH.

Hail in JASPER, IOWA
From 06-AUG-13 17:56:00 to 06-AUG-13 17:56:00 (CST-6)
Location: VANDALIA
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 15.00K
Reported by: Public

Hail in JASPER, IOWA
From 06-AUG-13 18:10:00 to 06-AUG-13 18:10:00 (CST-6)
Location: MONROE
Magnitude: 2.50 
Property damage: 25.00K
Crop damage: 15.00K
Reported by: Social Media

Hail in JASPER, IOWA
From 06-AUG-13 18:15:00 to 06-AUG-13 18:15:00 (CST-6)
Location: MONROE
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 15.00K
Reported by: Public

Hail in JASPER, IOWA
From 06-AUG-13 18:17:00 to 06-AUG-13 18:17:00 (CST-6)
Location: MONROE
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CASS, IOWA
From 06-AUG-13 23:47:00 to 06-AUG-13 23:47:00 (CST-6)
Location: MASSENA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Hail in MAHASKA, IOWA
From 06-AUG-13 23:55:00 to 06-AUG-13 23:55:00 (CST-6)
Location: OSKALOOSA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Broadcast Media

Hail in ADAMS, IOWA
From 07-AUG-13 00:11:00 to 07-AUG-13 00:11:00 (CST-6)
Location: WILLIAMSON
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 15.00K
Reported by: Public

Hail in ADAMS, IOWA
From 07-AUG-13 00:18:00 to 07-AUG-13 00:18:00 (CST-6)
Location: PRESCOTT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Trained Spotter

Small branches were also downed by the storm.

Hail in MAHASKA, IOWA
From 07-AUG-13 00:35:00 to 07-AUG-13 00:35:00 (CST-6)
Location: OSKALOOSA
Magnitude: 1.00 
Property damage: 0.00K
Crop damage: 10.00K
Reported by: Broadcast Media

Thunderstorm Wind in JASPER, IOWA
From 06-AUG-13 17:56:00 to 06-AUG-13 17:56:00 (CST-6)
Location: VANDALIA
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Public

Estimated wind gusts by the public.  Tree limb damage reported.

Heavy Rain in ADAMS, IOWA
From 07-AUG-13 00:25:00 to 07-AUG-13 00:25:00 (CST-6)
Location: STRINGTOWN
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Rainfall of 2.10 inches overnight.

Thunderstorm Wind in TAMA, IOWA
From 07-AUG-13 00:42:00 to 07-AUG-13 00:42:00 (CST-6)
Location: CHELSEA
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 3 to 5 inch diameter branches down.

Thunderstorm Wind in TAMA, IOWA
From 07-AUG-13 00:43:00 to 07-AUG-13 00:43:00 (CST-6)
Location: CHELSEA
Magnitude: 52.00 EG
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trained spotter reported 60 MPH winds with 3 to 4 inch diameter branches down.

Thunderstorm Wind in TAMA, IOWA
From 07-AUG-13 00:44:00 to 07-AUG-13 00:44:00 (CST-6)
Location: CHELSEA
Magnitude: 52.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Public

High winds downed trees.

Hail in JASPER, IOWA
From 06-AUG-13 18:10:00 to 06-AUG-13 18:10:00 (CST-6)
Location: MONROE
Magnitude: 2.00 
Property damage: 20.00K
Crop damage: 0.00K
Reported by: Public

Thunderstorm Wind in ADAMS, IOWA
From 07-AUG-13 00:18:00 to 07-AUG-13 00:18:00 (CST-6)
Location: PRESCOTT
Magnitude: 56.00 EG
Property damage: 5.00K
Crop damage: 25.00K
Reported by: Public

A large tree several feet in diameter was blown down in a yard.  Surrounding corn fields had stalk damage with stripped leaves due to hail and wind.

Hail in JASPER, IOWA
From 06-AUG-13 18:15:00 to 06-AUG-13 18:15:00 (CST-6)
Location: MONROE
Magnitude: 2.00 
Property damage: 100.00K
Crop damage: 0.00K
Reported by: Trained Spotter