A very dynamic weather pattern set up over the central U.S. during the day on the 9th. A deep trough formed aloft over the southeast U.S. with a strong southwest flow setting up over Iowa at all levels.  During the afternoon and evening, the low level jet increased steadily and reached 50 to 70 kts by midnight.  Considerable moisture advection took place with surface dewpoints rising into the low to middle 60s by evening.  A strong warm front lifted north into Iowa during the afternoon.  By the early evening hours it extended from west central Iowa into the east central and southeast counties of the state.  This front served as a focusing mechanism for thunderstorm development.  A strong elevated mixed layer was in place over the state during the afternoon of the 9th.  This kept convection from developing until the evening hours.  The freezing level was quite high for mid April, around 13,000 feet.  By early evening, at the initiation of storm development, the atmosphere had become very unstable.  Lifted indices were in the -9 to -12 C range with elevated CAPE feeding into the state in the 3000 to 5000 J/kg range.  The atmosphere was very sheared with effective shear of 60 to 65 kts.  As the moisture increased, precipitable water values increased to between 0.8 and 1.1 inches.  There was considerable downdraft CAPE available, with 1100 J/kg available.  CAPE in the -10 to -30 C layer of the atmosphere was between 500 and 1000 J/kg.  The effective helicity in the low layers of the atmosphere was around 800 J/Kg.  The LCL was around 1250 meters.  Thunderstorms developed along the warm frontal boundary during the very late afternoon and evening hours.  The storms formed more as discrete supercells rather than forming into a line.  The strongest supercells moved through Onawa County along the northern Crawford County line into Sac County.  Another strong supercell moved through Kossuth County.  In addition to the tornadoes that occurred, there were scattered reports of hail ranging from golf ball to baseball size with the storms.  There were a few reports of wind damage, however most of the damage that occurred was tornadic in nature.  On the north edge of the storms, what appeared to be a gravity wave lifted northeast along the back side of the line.  It produced a wind gust of near 60 MPH for a short period of time in Emmet County.  Several tornadoes touched down across western into northwest Iowa.  In Sac County, an EF3 tornado touched down with peak winds of 140 MPH. The path length was about 13 miles long and reached a mile in width at its widest.  The tornado began north of Odebolt and ended about 6 miles northwest of Early.  Damage was done to a farmstead and one home was totally destroyed.  Shortly before that, a tornado touched down in Crawford County from northwest of Ricketts to to about 4 miles northeast of Schleswig.  Damage was done to farmsteads along its path.   Another tornado touched down in Sac County northwest of Odeboldt and tracked to just northeast of Early.  This tornado had winds of 132 MPH, EF2 strength, with a half mile wide peak width.  It was on the ground for about 13 miles.  In what was the longest tornado track of the day, about 30 miles in length, a tornado touched down just west of Nemaha and tracked to about 3 1/2 miles southwest of Havelock through Sac, Buena Vista, and Pocahontas Counties.  The tornado was EF3 in strength and had a peak width of 2 to 3 miles.  Major damage occurred along the route with hog buildings destroyed, several farmsteads damaged or destroyed, and residential damage reported.  A turkey containment was destroyed, with the building completely removed.  Numerous hogs died in the tornado was well.  There were at least 4 satellite tornadoes associated with this long track tornado.  Two of the satellite tornadoes were a cyclonic/anticyclonic pair as they pushed north into Pocahontas County.  Another tornado, related to the same parent cell, tracked southeast and crossed paths with the long track tornado in Pocahontas County.  This tornado had peak winds of 170 MPH and was rated EF4.  Several farmsteads were destroyed by the tornado.  The path width was nearly 600 yards wide.  Yet another tornado touched down in Sac County northwest of Nemaha, and tracked to about 9 miles northeast of Nemaha.  It was on the ground for about 12 miles and had a peak width of 1/2 mile.  Damage was done to farms and a hog confinement building.  In Kossuth County, a tornado touched down briefly south of Algona and was on the ground for about a mile.  It was 200 yards wide and was EF1 strength with 90 MPH winds.  A smaller tornado touched down briefly southwest of Algona in Kossuth County.  Damage occurred to a hog confinement building and to power lines.  Following the NWS storm survey, there were two other tracks of EF-0 strength tornadoes discovered.  One occurred in farm fields of Sac County, north-northwest of Odebolt.  The path was about a mile long and 200 yards wide at its widest, with peak winds estimated at 65 MPH.  The tornado had an erratic track which actually looped back on itself.  Another tornado touched down in farm fields in Pocahontas County.  It was also an EF-0 tornado with a path length of about 2.5 miles and maximum width of 250 yards.  Winds with the tornado were around 100 MPH.  Governor Terry Branstad proclaimed a State Disaster Declaration for Buena Vista, Sac, Calhoun, and Pocahontas Counties.

Tornado in POCAHONTAS, IOWA
From 09-APR-11 20:31:00 to 09-APR-11 21:07:00 (CST-6)
Location: FONDA
Tornado F-scale: EF3
Property damage: 10.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This is a continuation of a large wedge tornado. This tornado started in Sac County, clipped southeast Buena Vista County and continued in Pocahontas County.  This tornado continued to produce numerous satellite tornadoes through Pocahontas County.  This produced an unusual and varying debris field.

High Wind in EMMET, IOWA
From 09-APR-11 20:00:00 to 09-APR-11 22:00:00 (CST-6)
Magnitude: 52.00 MG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: ASOS

Hail in SAC, IOWA
From 09-APR-11 19:41:00 to 09-APR-11 19:41:00 (CST-6)
Location: EARLY
Magnitude: 1.75 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SAC, IOWA
From 09-APR-11 19:48:00 to 09-APR-11 19:48:00 (CST-6)
Location: EARLY
Magnitude: 1.25 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in SAC, IOWA
From 09-APR-11 19:48:00 to 09-APR-11 19:48:00 (CST-6)
Location: SCHALLER
Magnitude: 1.75 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Trees and power lines were also downed.

Hail in SAC, IOWA
From 09-APR-11 20:08:00 to 09-APR-11 20:08:00 (CST-6)
Location: EARLY
Magnitude: 2.00 
Property damage: 15.00K
Crop damage: 0.00K
Reported by: Storm Chaser

Windshields were broken.

Hail in POCAHONTAS, IOWA
From 09-APR-11 21:03:00 to 09-APR-11 21:03:00 (CST-6)
Location: WARE
Magnitude: 1.00 
Property damage: 2.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POCAHONTAS, IOWA
From 09-APR-11 21:09:00 to 09-APR-11 21:09:00 (CST-6)
Location: POCAHONTAS
Magnitude: 1.50 
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in POCAHONTAS, IOWA
From 09-APR-11 21:35:00 to 09-APR-11 21:35:00 (CST-6)
Location: LAURENS
Magnitude: 2.75 
Property damage: 75.00K
Crop damage: 0.00K
Reported by: Public

The public reported baseball size hail and some minor urban flooding.

Hail in WORTH, IOWA
From 09-APR-11 22:00:00 to 09-APR-11 22:00:00 (CST-6)
Location: NORTHWOOD MUNI ARPT
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in PALO ALTO, IOWA
From 09-APR-11 22:30:00 to 09-APR-11 22:30:00 (CST-6)
Location: EMMETSBURG
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Nickel to quarter size hail reported.

Hail in KOSSUTH, IOWA
From 09-APR-11 22:32:00 to 09-APR-11 22:32:00 (CST-6)
Location: ALGONA
Magnitude: 2.00 
Property damage: 50.00K
Crop damage: 0.00K
Reported by: Storm Chaser

A funnel cloud was also reported.

Hail in KOSSUTH, IOWA
From 09-APR-11 22:51:00 to 09-APR-11 22:51:00 (CST-6)
Location: SENECA
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in KOSSUTH, IOWA
From 09-APR-11 23:10:00 to 09-APR-11 23:10:00 (CST-6)
Location: LONE ROCK
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Hail in KOSSUTH, IOWA
From 09-APR-11 23:21:00 to 09-APR-11 23:21:00 (CST-6)
Location: BANCROFT
Magnitude: 1.00 
Property damage: 3.00K
Crop damage: 0.00K
Reported by: Law Enforcement

Thunderstorm Wind in WORTH, IOWA
From 09-APR-11 21:39:00 to 09-APR-11 21:39:00 (CST-6)
Location: FERTILE
Magnitude: 57.00 EG
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

A grain bin was blown over with power lines also downed.

Tornado in SAC, IOWA
From 09-APR-11 19:23:00 to 09-APR-11 19:55:00 (CST-6)
Location: ODEBOLT
Tornado F-scale: EF3
Property damage: 2.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

Tornado moved northeast for nearly 4 miles before abruptly turning north northwest for the remainder of the path.  Lots of debris and power outages.  Numerous homes damaged or destroyed.

Tornado in KOSSUTH, IOWA
From 09-APR-11 22:19:00 to 09-APR-11 22:21:00 (CST-6)
Location: ST JOSEPH
Tornado F-scale: EF1
Property damage: 150.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Short duration tornado that produced damage to a hog confinement building.

Tornado in SAC, IOWA
From 09-APR-11 20:24:00 to 09-APR-11 20:26:00 (CST-6)
Location: NEMAHA
Tornado F-scale: EF2
Property damage: 500.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This was the first satellite tornado that developed in far northern Sac County producing a narrow but strong swath of damage as it crossed into Buena Vista County.

Tornado in CRAWFORD, IOWA
From 09-APR-11 18:37:00 to 09-APR-11 18:38:00 (CST-6)
Location: RICKETTS
Tornado F-scale: EF1
Property damage: 25.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Reports of power lines taken down by tornado.

Tornado in SAC, IOWA
From 09-APR-11 19:38:00 to 09-APR-11 19:40:00 (CST-6)
Location: EARLY
Tornado F-scale: EF0
Property damage: 1.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

Brief tornado that did a small loop as it tracked just west of due north.  Stayed primarily in agricultural fields.

Tornado in POCAHONTAS, IOWA
From 09-APR-11 21:08:00 to 09-APR-11 21:13:00 (CST-6)
Location: WESTVIEW
Tornado F-scale: EF1
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This relatively brief tornado travelled mostly through open country with limited damage.

Tornado in POCAHONTAS, IOWA
From 09-APR-11 20:55:00 to 09-APR-11 20:58:00 (CST-6)
Location: VARINA
Tornado F-scale: EF1
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This was a cyclonic tornado of a pair of tornadoes that travelled on the east side of a large wedge tornado that moved through Pocahontas County.

Tornado in POCAHONTAS, IOWA
From 09-APR-11 20:55:00 to 09-APR-11 20:58:00 (CST-6)
Location: VARINA
Tornado F-scale: EF1
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

This was the anticyclonic tornado of a pair of tornadoes that moved on the east side of a large wedge tornado passing through western Pocahontas County.

Tornado in POCAHONTAS, IOWA
From 09-APR-11 20:56:00 to 09-APR-11 20:58:00 (CST-6)
Location: VARINA
Tornado F-scale: EF2
Property damage: 100.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A short but relatively intense tornado.  This was a satellite tornado to a large wedge tornado that moved through western Pocahontas County.  This tornado became absorbed into the circulation of another powerful satellite tornado that moved in from the west.

Thunderstorm Wind in WORTH, IOWA
From 09-APR-11 21:30:00 to 09-APR-11 21:30:00 (CST-6)
Location: TENOLD
Magnitude: 61.00 EG
Property damage: 300.00K
Crop damage: 0.00K
Reported by: Newspaper

Large barn destroyed with damage of $250,000-300,000.

Tornado in POCAHONTAS, IOWA
From 09-APR-11 20:54:00 to 09-APR-11 21:01:00 (CST-6)
Location: VARINA
Tornado F-scale: EF4
Property damage: 2.50M
Crop damage: 0.00K
Reported by: NWS Storm Survey

An intense EF4 satellite tornado on the west flank of a large wedge tornado passing through western Pocahontas county.  This tornado approached from the northwest and completely destroyed a home leaving little debris at the site.  Grove of mature hardwood trees near the home was decimated and debarked and a large combine in the machine shed was tossed and rolled several hundred feet.  This tornado also absorbed the circulation of an EF2 satellite tornado.

Tornado in SAC, IOWA
From 09-APR-11 19:29:00 to 09-APR-11 19:54:00 (CST-6)
Location: ODEBOLT
Tornado F-scale: EF2
Property damage: 1.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

Multiple homes damaged along the track of the storm.  Storm passed through the town of Early before quickly dissipating.

Tornado in SAC, IOWA
From 09-APR-11 20:08:00 to 09-APR-11 20:24:00 (CST-6)
Location: NEMAHA
Tornado F-scale: EF2
Property damage: 2.00M
Crop damage: 0.00K
Reported by: NWS Storm Survey

This long track tornado touched down in Sac County and crossed the border into Buena Vista County.  This large tornado occurred in conjunction with many satellite tornadoes producing a large and varying debris field.