A destructive and deadly three-day-long tornado outbreak impacted the central and lower Mississippi Valley from December 30, 2010, to January 1, 2011. Associated with a low pressure system and a strong cold front, 37 tornadoes tracked across five states over the length of the severe event, killing nine and injuring several others. Activity was centered in the states of Missouri and later Mississippi on December 31. Seven tornadoes were rated EF3 on the Enhanced Fujita Scale; these were the strongest during the outbreak. Non-tornadic winds were recorded to have reached as high as 80 mph (130 km/h) at eight locations on December 31, while hail as large as 2.75 in (7.0 cm) was documented north-northeast of Mansfield, Missouri. Damage estimates from the outbreak totaled US$136.98 million. This is the most prolific tornado outbreak in Missouri in the month of December.
The United States Storm Prediction Center first noted a possible New Year's Eve severe weather event as early as December 25, 2010. These forecasts gained confidence as the event approached, with a focus on the Ozarks and adjacent areas. Supercells developed in this area during the night of December 30 and tracked across central Missouri, producing several tornadoes and large hail. However, the bulk of activity during the outbreak was a result of a long line of supercells that tracked from Oklahoma to Illinois, producing five EF3 tornadoes. One of these tracked through northwestern Arkansas, killing four. Another tore through eastern sections of Fort Leonard Wood in Missouri, destroying 159 homes and causing US$90 million in damage, making it the costliest tornado of the outbreak. A separate cluster of storms later developed in Louisiana before tracking into Mississippi, producing several tornadoes across southern and central regions of the state on January 1.
The Storm Prediction Center (SPC) began to note the possibility that a severe weather event could develop on December 30 as early as December 25, 2010. Nonetheless, the predictability of the event was too low as the event was several days out. As the anticipated event grew closer, confidence in the forecast slowly increased, though uncertainties in the timing and extent of the tornado outbreak still existed. These uncertainties remained through December 29 with forecasts calling for only marginal hail and possibly damaging gusts. However, the SPC indicated that discrete tornadic supercells and more severe thunderstorms could result from atmospheric conditions deviating slightly from the forecast. In contrast, forecasts were more confident in a widespread outbreak of severe weather for New Year's Eve; the SPC issued a slight risk outlook for much of the Lower Mississippi Valley and the Ozarks as a result.
Atmospheric conditions remained only marginally conducive for the development of thunderstorms on the morning of December 30. Throughout the day, moisture was drawn from the Gulf of Mexico northward into the Ozarks region. However, the presence of a capping inversion prevented thunderstorms from developing. During the evening of December 30, an area of strong wind shear developed near the Ark-La-Tex and southeastern Oklahoma area well ahead of a nearing cold front, providing a focal point for potential storm development. Late that day, scattered thunderstorms developed over eastern Oklahoma and northern Arkansas, producing significant hail. Over the next few hours and into December 31, these storms would intensify as they moved into southwestern Missouri, producing four tornadoes. The first tornado watch issued in association with the severe event was issued at 07:06 UTC on December 31 as these storms tracked across the Ozarks. After a few hours, these supercell thunderstorms lessened in strength as they neared the Greater St. Louis metropolitan area.
While the cluster of thunderstorms was tracking through Missouri, a new squall line with embedded supercells developed across eastern Oklahoma and Kansas, demarcating a dry line boundary. Although linear storm systems tend to indicate strong wind events and not tornadoes, these storms tracked eastward into southwestern Missouri and eventually produced several tornadoes. A long-tracked EF3 developed from one of these supercells and struck Cincinnati, Arkansas. At 13:31 UTC on December 31, a tornado watch was issued for much of Missouri and portions of Arkansas and Illinois. Most of the tornadoes during the outbreak stemmed from this line of storms as they moved through Missouri and Illinois throughout the day. At around noon, a new cluster of disorganized showers formed over eastern Louisiana and southern Mississippi. Although these storms were initially weak, they gradually intensified into supercells as the day went on. Additional supercells quickly developed over Louisiana and eventually spread in coverage over Mississippi, resulting in the development of several tornadoes. Reaching their peak strength over Mississippi, the storms gradually lost their intensity as they tracked eastward late on December 31 and into January 1, 2011. By the morning hours of January 1, severe activity had become restricted to the Florida Panhandle and southern Alabama; the last tornado watch issued in association with the 2010 New Year's Eve tornado outbreak was issued for those regions at 15:56 UTC that day.
The deadliest tornado of the 2010 New Year's Eve tornado outbreak moved across extreme eastern Oklahoma and northwestern Arkansas, tracking 21.1 mi (34.0 km) and damaging the unincorporated community of Cincinnati, Arkansas. The first tornado warning associated was issued at 12:00 UTC for portions of Adair County in Oklahoma and Benton and Washington counties in Arkansas by the National Weather Service Tulsa, Oklahoma. At around the same time, damaging winds estimated at 70 mph (110 km/h) tore the roof off of a barn southwest of Westville, Oklahoma; these winds were likely a result of inflow caused by the developing tornado. Post-tornado survey teams concluded that the tornado touched down five minutes later northeast of Westville. Quickly tracking northeast, the tornado snapped 13 large wooden utility poles. Four cars were displaced by 20–50 yd (18–46 m), and a nearby home sustained significant roof damage and broken windows; this resulted in an EF2 rating for the tornado within Adair County. Damage in Adair County totaled $60,000. At 12:08 UTC, the tornado crossed the Oklahoma-Arkansas border and moved into Benton County, Arkansas.
At 12:10 UTC, the tornado tracked into Cincinnati, where it reached its peak intensity. Winds were estimated as high as 142 mph (229 km/h), making the tornado a low-end EF3 at this location, and the tornado widened to a width of 300 yd (270 m). Several homes were destroyed or heavily damaged in the southwestern areas of the town. Numerous trees and power poles were knocked down or uprooted. Two people were killed when a mobile home was destroyed, while another person died as he was tending cattle when the barn he occupied collapsed. Seven others were injured in Cincinnati. The tornado continued to widen as it trekked northeastward, reaching a maximum width of 500 yd (460 m). Several permanent homes were heavily damaged northeast of Cincinnati, and a number of chicken houses, mobile homes, outbuildings, and power poles were destroyed. One woman was critically injured after her mobile home was destroyed; she died of her injuries at a hospital four days later. Damage in Cincinnati and surrounding areas within Benton County reached $1.5 million.
After passing near Weddington at around 12:17 UTC, the tornado crossed over the Benton–Washington county line four times as it continued northeastward. Permanent houses were damaged, mobile homes were destroyed, numerous trees were uprooted or snapped, and many other power poles were snapped. Two people were injured following the destruction of a mobile home within the Ozark National Forest in Benton County, while another person was injured west of Tonitown in Washington County. The tornado finally dissipated northwest of Tontitown at 12:27 UTC after causing four deaths and 10 injuries. Overall, the tornado caused $1.835 million in damage, which was the sixth costliest total during the tornado outbreak.