The March 2009 tornado outbreak sequence was a series of tornado outbreaks which affected large portions of the Central, Southern, and Eastern United States from March 23 to March 29. A total of 56 tornadoes touched down during the event, two of which were rated as EF3.

An upper trough moved from the Four Corners region into the southern Great Plains and lower Missouri Valley during the day on March 23. During this, a surface low in western portions of Nebraska pushed into eastern South Dakota. A cold front combined with the low moved across the central and southern Great Plains and was the main area where thunderstorm development would occur. Although moisture was limited, strong wind shear created favorable conditions for supercells to develop and rotate. As a result, the supercells had the potential to produce tornadoes.^[1] A moderate risk of severe weather was issued for portions of central and eastern Kansas and northern Oklahoma.^[2] During the day, a fast-moving supercell produced several tornadoes in eastern Nebraska and across the state line into the west central portion of Iowa. Five tornadoes occurred in eastern Nebraska, with eight people injured in Eagle. In Iowa, an EF2 tornado destroyed one home, damaged another home, a barn and seven outbuildings and derailed 54 empty grain rail cars in Harrison County. The supercell then moved into Montgomery County, where it produced two EF0 tornadoes.^[3]

Several days of severe weather began with an EF1 tornado near Meridian, Mississippi on March 25. During the early morning hours of March 26, severe thunderstorms produced six tornadoes in central sections of Mississippi. The most powerful tornado spawned was an EF3 that struck Magee. Sixty homes were either damaged or destroyed with 25 people injured from the tornado. A church was destroyed and a warehouse was severely damaged. An EF2 tornado, three EF1, and an EF0 also occurred as the severe weather moved through the area.^[4] A state of emergency was declared for 12 counties by the Governor of Mississippi Haley Barbour.^[5] The thunderstorms also produced three tornadoes, one rated EF1 and the other two rated EF0, in southeastern Louisiana and coastal regions of Mississippi. The EF1 tornado damaged seven homes, extensively damaged one trailer and injured one person in Tangipahoa Parish.^[6]

Another round of severe weather developed late that evening, producing another intense squall line with embedded tornadoes across the northern Gulf Coast region early on March 27, where several tornadoes were reported.^[7] Later during the afternoon, various tornadoes developed in North Carolina, causing structural damage in eastern North Carolina.^[8][9][10] The tornadoes formed after a disturbance moved into the area from Alabama.^[11] One of the tornadoes near Parkton was rated as an EF2 and injured one person.^[12]

On March 28, a strong 997 millibar upper-level low pressure area located over Oklahoma was forecast to produce widespread thunderstorms, with a moderate risk of severe weather in most of northern Louisiana, much of Mississippi, and southern Arkansas. A warm front was likely to develop along the leading edge of the system, allowing for atmospheric instability, a necessary component of severe thunderstorms. In areas farther north, relatively cool temperatures were anticipated to limit convective activity but very strong dynamics in the area would allow storms to develop. This would allow a thunderstorm which became separated from the main squall line to become severe and possibly tornadic.^[13] Later in the day, the Storm Prediction Center (SPC) issued a slight risk for a large area which encompassed much of the Southeast United States. Tornadic activity was less imminent due to lower due points but strong wind shear was able to provide fuel for severe storms.^[14]

More tornadoes occurred on March 28, as they affected Tennessee and Kentucky during the afternoon. A supercell that tracked through three different counties in western areas of Kentucky produced two tornadoes. One of them was an EF3 tornado that destroyed six homes, caused major damage to 10 homes and minor damage to 60 homes and businesses in Corydon.^[15] In Tennessee, an EF1 tornado caused damage to several businesses in Murfreesboro, including the local Boys and Girls Club and a shopping plaza, which was heavily damaged. Another EF1 tornado destroyed a modular home and damaged three other homes in Ashland City.^[16]

Severe thunderstorms caused widespread damage throughout Pennsylvania on March 29.^[17] An EF1 tornado was produced in Lancaster County, damaging 238 structures across a path of 10 miles (16 km) from Lititz to Denver, most of which were 200 homes that were damaged by hail. Thirty barns suffered moderate damage, one barn sustained major damage, six trailer homes were destroyed with two others suffering major damage. Three people were injured by the tornado, which altogether cost an estimated $3 million in damage.^[18]

• List of North American tornadoes and tornado outbreaks