A very dynamic weather pattern was set up over Iowa during the afternoon of the 4th into the evening hours.  A closed upper low was located to west of Iowa with a negatively tilted trough lifting northeast through the state.  A strong area of low pressure developed at the surface over south central Nebraska.  The surface low moved north into southeast South Dakota during the evening and overnight hours.  A cold front from the low advanced across the state as the low lifted.  In addition, several boundaries were present during the mid afternoon hours.  An outflow boundary extended east to west along the Iowa-Missouri border, with the synoptic warm front extending east to west across northern Iowa.  The atmosphere was very unstable with most unstable CAPE values of 2000 to 3000 J/kg pushing into Iowa from the south.  Downdraft CAPE was between 600 and 1000 J/kg.  Lifted indices along and south of the southern boundary were between -5 and -10 C.  The atmosphere was strongly sheared with 50 kts of effective shear available.  With the boundary remaining over southern Iowa through the afternoon, the LCL level was quite low, between 500 and 1000 meters.  Very high precipitable water values of 1.5 inches were present.  The freezing level was quite high for early October at 13,000 to 13,500 feet.  CAPE available in the -10 to -30 C layer of the atmosphere was between 400 and 800 J/kg.  An initial round of thunderstorms developed north of the warm front during the mid afternoon hours.  They produced heavy rain and some small hail.  The largest hail was penny size in Dallas County.  Storms produced heavy rainfall as well with 1.2 inches falling northeast of Grinnell in a short period of time.  The next wave of thunderstorms developed over north central Iowa.  The storms produced hail and reports of one to one and one half inch diameter hail occurred with them.  As the dry line moved toward the state, a line of strong thunderstorms developed over west central into north central Iowa.  Severe weather was quite limited however.  Golf ball size hail was reported in Calhoun County south of Pomeroy, and high winds caused considerable damage in the Lone Rock area of Kossuth County.  In addition, winds near 85 MPH downed high tension power poles along Highway 15 south of Fenton.

Hail in DALLAS, IOWA
From 04-OCT-13 13:34:00 to 04-OCT-13 13:34:00 (CST-6)
Location: MORAN
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Amateur Radio

Reported at the intersection of Highway 141 and County Road R22.

Heavy Rain in POWESHIEK, IOWA
From 04-OCT-13 15:28:00 to 04-OCT-13 15:28:00 (CST-6)
Location: GRINNELL
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

A total of 1.2 inches of rain fell from late morning into early afternoon thunderstorms.

Hail in CERRO GORDO, IOWA
From 04-OCT-13 17:14:00 to 04-OCT-13 17:14:00 (CST-6)
Location: THORNTON
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CERRO GORDO, IOWA
From 04-OCT-13 17:38:00 to 04-OCT-13 17:38:00 (CST-6)
Location: MASON CITY
Magnitude: 1.50 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Sheriff's department reported hail up to ping pong ball size.

Hail in CERRO GORDO, IOWA
From 04-OCT-13 17:40:00 to 04-OCT-13 17:40:00 (CST-6)
Location: MASON CITY
Magnitude: 1.25 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CERRO GORDO, IOWA
From 04-OCT-13 17:40:00 to 04-OCT-13 17:40:00 (CST-6)
Location: MASON CITY
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in CERRO GORDO, IOWA
From 04-OCT-13 17:42:00 to 04-OCT-13 17:42:00 (CST-6)
Location: MASON CITY
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Broadcast Media

Nickel to quarter size hail was reported by KIMT-TV.

Hail in CALHOUN, IOWA
From 04-OCT-13 20:05:00 to 04-OCT-13 20:05:00 (CST-6)
Location: POMEROY
Magnitude: 1.75 
Property damage: 20.00K
Crop damage: 10.00K
Reported by: Social Media

Hail in PALO ALTO, IOWA
From 04-OCT-13 20:14:00 to 04-OCT-13 20:14:00 (CST-6)
Location: RUTHVEN
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Social Media

Thunderstorm Wind in KOSSUTH, IOWA
From 04-OCT-13 20:50:00 to 04-OCT-13 20:50:00 (CST-6)
Location: LONE ROCK
Magnitude: 61.00 EG
Property damage: 30.00K
Crop damage: 0.00K
Reported by: Law Enforcement

The Kossuth County dispatch reported a large tree down on a house.  The trees canopy covered at least one room of the house.

Thunderstorm Wind in KOSSUTH, IOWA
From 04-OCT-13 20:40:00 to 04-OCT-13 20:40:00 (CST-6)
Location: LONE ROCK
Magnitude: 61.00 EG
Property damage: 50.00K
Crop damage: 50.00K
Reported by: Emergency Manager

Multiple trees and branches were blown down. Power poles were blown down.  The tops of trees were sheared off on a farm near Lone Rock with crop damage reported.

Thunderstorm Wind in KOSSUTH, IOWA
From 04-OCT-13 20:40:00 to 04-OCT-13 20:40:00 (CST-6)
Location: FENTON
Magnitude: 73.00 EG
Property damage: 75.00K
Crop damage: 50.00K
Reported by: Emergency Manager

High transmission power poles were down along highway 15.