Tornado outbreak of April 9–11, 2011

A large storm system with an associated frontal boundary moved northward and eastward across the central United States beginning on April 8. While initial severe weather was limited, a lone supercell broke out ahead of a mesoscale convective system in Pulaski County, Virginia on the eastern end of the warm front that evening. Two tornadoes were confirmed, one of which was an EF2 that caused severe damage in Pulaski, Virginia. Numerous houses were damaged and eight people were injured. An outbreak began across the United States during the afternoon of April 9; supercells developed along the warm front and tracked through parts of Kentucky, Tennessee, Virginia, and North Carolina, generating softball sized hail and eight more tornadoes. A warm front began developing along the southeastern side of the low pressure area as it moved over The Dakotas. During the evening hours of April 9, the SPC issued a tornado watch for western and northern Iowa, eastern Nebraska and southeast South Dakota. Conditions within this region were favorable for the development of multiple tornadic storms and there was a 70 percent chance of multiple touchdowns. Around 22:50 UTC (5:50 p.m. CDT), a strong thunderstorm developed over Burt/Cuming Counties in northeastern Nebraska. This cell slowly tracked east-northeastward and developed into a supercell as it moved into Monona County, Iowa. At 00:20 UTC (7:20 p.m. CDT), a small tornado touched down roughly southwest of Mapleton. Within minutes, this storm quickly grew and intensified as it moved closer to the city. The tornado passed directly over the city at low-end EF3 strength. Turning northward, the tornado dissipated about north of Mapleton. A separate EF2 tornado struck the town of Early, where considerable damage occurred to homes and businesses. EF2 tornado damage, one year later Tracking northeastward, the supercell moved into Ida County, another tornado touched down around 01:20 UTC (8:20 p.m. CDT) to the west of Arthur. This storm remained on the ground for eight minutes, during which it damaged a few structures, before dissipating northwest of Arthur. Around the same time, the cell entered Sac County and the first in a series of multiple tornadoes touched down northwest of Odebolt. Over the following three hours, 14 tornadoes touched down across Sac, Buena Vista, and Pocahontas counties. At 02:08 UTC (9:08 p.m. CST), a wide EF3 tornado touched down in northern Sac County. Remaining on the ground for an hour, this tornado meandered along a path, producing several satellite tornadoes, including a short-lived EF4 tornado west of Pocahontas. Officials blocked off the town and Governor Terry Branstad issued a disaster proclamation for the town. Early estimates indicated that 60% of the town was damaged and 20% was nearly flattened. Despite the damage, only three people sustained minor injuries. On April 10, another moderate risk was issued. A PDS Tornado Watch was issued for parts of Minnesota, Michigan, and Iowa, as well as most of Wisconsin. With 16 confirmed tornadoes in Wisconsin, the outbreak ranked as the largest single-day event in April in the state. Severe damage occurred in the towns of Merrill, Kaukauna, and Cottonville. On the evening of April 10, a number of tornado watches and warning were issued stretching from southern Oklahoma to Sault. Ste. Marie, Michigan as well as central Ontario which became Canada's first tornado watch of the season. Thunderstorm watches and warnings were also reported as far away as northern and northwestern Ontario. ==Confirmed tornadoes==

April 9 event April 10 event April 11 event Mapleton, Iowa Prior to the first tornado of the evening in Iowa on April 9, a tornado warning was issued by the National Weather Service in Omaha, Nebraska at 7:08 p.m. CDT (12:08 UTC) for northeastern Monona County. Approximately 16 minutes later, a tornado touched down southwest of Mapleton. This large, powerful and dusty tornado began at EF0 intensity, near IA 175. The tornado then steadily increased to EF1 intensity as it moved along the highway, just a few minutes before impacting the southwest side of Mapleton. Trees along this stretch of the highway were snapped or uprooted as the tornado encroached on the Maple River. Much of the early warning was helped by storm chasers and spotters, giving many residents around 15 minutes of lead time to take cover before the tornado struck Mapleton. Nemaha–Newell–Pocahontas County, Iowa Later after dusk settled, the supercell which produced the Mapleton tornado, and a few large and strong tornadoes, dropped this massive and long-lived EF3 wedge tornado at 9:08 p.m. CDT (02:08 UTC) to the west of Nemaha in northern Sac County, following the dissipation of an EF2 tornado that went through the small city of Early. The massive tornado at this point, reached a width of as it damaged one farmstead at EF2 intensity along an path within Sac County. After exiting Sac County into Buena Vista County, a narrow EF2 satellite tornado developed at 9:24 p.m. CDT (02:24 UTC) on the east flank of the main tornado tornado, south of the Sac-Buena Vista County line. This tornado, with estimated winds of lasted for 3 minutes, but damaged trees and buildings on a farm before dissipating along a path, and causing $510,000 USD in damage to the property. The wedge tornado traversed along a path through extreme southeastern Buena Vista County, shrinking down to and causing EF2 damage to several farms and powerlines. Livestock shelters and farm equipment in this section of the path were destroyed as well southeast of Newell. The parent tornado then crossed Buena Vista County over into neighboring Pocahontas County afterwards. Barns and a machine shed were destroyed, as a combine harvester from the shed was tossed into a field away, before it was severely mangled. With estimated winds of , was this the strongest tornado of the event. The other satellites were an EF2 tornado with winds of , and a pair of EF1 tornadoes, one cyclonic and the other anticyclonic. The EF2 tornado touched down at 9:56 p.m. CDT (02:56 UTC) lasted for 2 minutes and traveled for , before being absorbed by the previous EF4 tornado. The main tornado then intensified further and reached its peak intensity, causing EF3 damage to one farmhouse and demolishing several outbuildings on the farm. More homes to the north were impacted at EF2 intensity, including one in Ware. Right after causing considerable damage in the community of Ware, the main EF3 tornado would start weakening and dissipate southwest of Havelock at approximately 10:07 p.m. CDT (03:07 UTC). The EF3 tornado that struck Varina and Ware alongside rural areas across Sac, Buena Vista and Pocahontas counties was the largest, longest lived and costliest tornado of the event as it caused $13 million USD in damages. The EF4 tornado in rural western Pocahontas County, was the strongest tornado of the night and of the entire outbreak from April 9–11. This violent satellite tornado caused $2.5 million USD in damage, tracked for and was 587 yards (0.33 mi; 0.54 km) wide. It was the first EF4 tornado to strike Iowa, since one impacted near Sibley on June 25, 2010. Two other pairs of satellite tornadoes, one group of two separate EF2 tornadoes, and a duo of cyclonic and anticyclonic EF1 twin tornadoes, also occurred and caused significant damage throughout the tri-county area. Despite the excessive tornadic activity, no fatalities or injuries were reported by this unique tornado event. ==Non-tornadic events==

Hail and wind event Accompanying the tornadoes, large hail and high winds also impacted parts of the Midwest. Initially, these events associated with the outbreak were confined to Iowa and parts of Nebraska and Minnesota on April 9. In Iowa, hail was measured up to in diameter, resulting in some damage to homes and cars. Roughly 3,200 insurance claims worth $12 million were later made in the city. Elsewhere in the state, winds up to downed numerous trees and power lines and in some instances tore roofs of buildings. In Texas, winds as high as caused extensive damage to homes and businesses, resulting in roughly $100 million in damage. Numerous trees were felled across the region and a few structures were destroyed. In Dallas County, a few carports collapsed. Near Venus, winds damaged five homes. Derecho event On April 11, a strong derecho brought widespread damage to much of northern Alabama as well as parts of Mississippi, Georgia and Tennessee. Near Brent, Alabama, a wind gust of was recorded up on a radio tower. ==Aftermath==

. Within days of the tornadoes in Iowa, excavators were brought in to clear debris and tear down homes that were damaged beyond repair. On May 5, nearly a month after the outbreak, President Barack Obama signed a federal disaster declaration for Buena Vista, Cherokee, Ida, Monona, Pocahontas and Sac Counties in Iowa. This allowed for government aid to be sent to the region and aid in recovery efforts. The declaration remained in effect until May 1, 2012. A disaster outreach center was opened on May 6 at the Mapleton City Hall and the American Legion Post in Varina and would remain open through May 26. At these places, residents would be allowed to apply for small business and homeowner loans up to $2 million and $200,000 respectively. In September 2019, Varina reopened their post office at a new location in the community eight years after the damaging EF3 tornado that tracked through Sac, Buena Vista and Pocahontas counties. Prior to its return, the community's postal office was temporarily relocated to Fonda for the time being. ==See also==