Late December 2012 North American storm complex

On December 24, the Storm Prediction Center (SPC) issued a moderate risk of severe weather, valid for the following day, as conditions became favorable for severe weather. The moderate risk covered an area stretching from west-central Louisiana to west-central Alabama and was expanded south and west on December 25 to include cities such as Port Arthur, New Orleans, and Mobile. From a meteorological standpoint, the outbreak was caused by a vigorous upper-level trough that moved southeast into Texas from the Rocky Mountains on the evening of December 24, becoming a powerful, negatively-tilted shortwave trough on December 25. In response to the shortwave trough, a surface low formed over south-central Texas by 1200 UTC that morning. Warm, moist air near the surface flowed northward along a warm front extending east from the surface low along the gulf coast on the morning of December 25. Meanwhile, a cold front and dry line had formed to the southwest of the surface low and advanced eastward through the morning, providing a source of lift for convection to form in eastern Texas. Later in the afternoon, enough energy associated with the advancing shortwave trough allowed for the formation of discrete tornadic supercells ahead of the advancing squall line in Louisiana, southern Mississippi, and southern Alabama, and around the same time, the SPC issued a Particularly Dangerous Situation (PDS) tornado watch for extreme eastern Louisiana, southern and central Mississippi, and western Alabama. Southerly winds near the surface increased, providing strong low-level and deep layer wind shear needed for these cells, which would later produce tornadic activity. By late-evening, most storms had congealed into a squall line and weakened due to waning instability. In the early morning of December 25, a mix of rain and snow began to develop as the upper-level trough began to interact with low-level moisture from the Gulf of Mexico. The system intensified as it moved across the southern plains and into the Mississippi Valley on Christmas Day. The system was able to pull in cold arctic air, causing snow and freezing rain in the south, leading to a rare "White Christmas" event for that portion of the country. As the system moved through the Tennessee Valley overnight into December 26, heavy snow continued in the Ohio Valley. A number areas in the Ohio Valley region, including Dayton, Ohio and Miamisburg, Ohio, and other locations, like Arkansas, also experienced thundersnow. As the day progressed, the system brought snow into the Great Lakes region, and a new low pressure center began to develop in North Carolina. Environment Canada also reported that the system began impacting Ontario that day, bringing heavy snow to the province. The system moved into the Northeast early December 27, with the upper-level trough moving just off the coast of the Delmarva Peninsula. At this point, the storm reached its lowest reported central pressure of . As the day progressed, the system began to weaken, with the pressure rising, as it continued to move to the northeast, impacting New England, as the system tracked toward the Canadian Maritimes overnight into December 28. That same day, Environment Canada reported heavy and blowing snow over Montreal, Quebec. Early on December 28, the system moved through Nova Scotia, bringing heavy rain and snow before it moved out over the Atlantic Ocean. During the next couple of days, the system slowly moved into the Atlantic Ocean, before accelerating eastward across the Atlantic on December 30. On December 31, the winter storm was absorbed by another extratropical cyclone, just northwest of the United Kingdom. ==Confirmed tornadoes==

McNeill–Maxie–McLain, Mississippi This strong and long-tracked EF3 tornado touched down in Pearl River County, just southwest of McNeill where it downed several trees at EF0 to EF1 intensity along Harris Road. It then rapidly intensified to high-end EF2 strength as it impacted the western edge of McNeill, where many trees were snapped and multiple houses were heavily damaged or destroyed. A small house along Joe Smith Road was left with only a few walls standing, and an elderly woman was critically injured inside. A nearby brick house had its roof torn off. A strong velocity couplet and debris ball became visible on Doppler weather radar by this time. The tornado reached its peak strength of EF3 as it crossed Stones Chapel Road at the north edge of town, where it destroyed a single-story brick triplex, with only two interior walls left standing. A nearby house was heavily damaged at EF2 strength, and a few others sustained lesser damage in the area. One house in McNeill that was damaged beyond repair had survived effects from both Hurricane Camille and Hurricane Katrina. It then weakened back to EF2 strength as it crossed US 11, snapping numerous trees and tearing the roofs off of some houses. The tornado weakened further and crossed I-59, moving through unpopulated rural areas southeast of Poplarville, causing EF0 to EF1 tree and outbuilding damage. The tornado then struck a house at EF1 strength near the Stone County line, causing heavy roof damage. Eight people were injured in Pearl River County, 22 houses were destroyed or damaged beyond repair, eight had major damage, 16 had minor damage, and an additional nine were affected in some way. The tornado strengthened to EF2 intensity again as it entered Stone County west of Texas, and caused significant damage to a few houses. Numerous pine trees were snapped at a campground in this area, and a mobile house and several more trees were downed before the tornado moved out of Stone County. The tornado then moved into Forrest County and produced high-end EF2 damage as it passed near the small community of Maxie, where numerous trees and power lines were downed, two double-wide mobile homes were completely destroyed, a pickup truck was rolled, and a camper was thrown about . Two additional double-wide mobile homes were severely damaged, a single-wide mobile home also sustained major damage, and a falling tree demolished a travel trailer. Four people were injured in Forrest County. The tornado momentarily weakened to EF1 intensity as it crossed into Perry County and moved through portions of the DeSoto National Forest, downing many trees. A house sustained considerable roof and window damage, outbuildings were destroyed, and two cars were moved along this segment of the path. It quickly regained EF2 status as it crossed MS 29 and snapped several wooden electrical transmission poles. The tornado then destroyed a mobile home and a hunting camp before weakening back to EF1 status, damaging a few homes, and downing many more trees. The path length through Perry County was about . The tornado continued northward and inflicted EF2 damage to several homes and Trinity Episcopal Church. At the church, part of a new slate roof was blown into the parking lot and a large portion of an exterior brick wall was knocked out, leaving a portion of the building visible from the outside. Homes in surrounding neighborhoods had their roofs torn off, large trees were snapped and uprooted, and gas leaks were reported in the area. The tornado widened to its widest point of along this portion of the path. The tornado continued to the north at EF2 intensity, ripping roofs off of homes as it crossed Springhill Avenue. By this point, a tornado emergency was declared for areas of Downtown Mobile at 2300 UTC (5:00 p.m. CST) as the large tornado approached those areas, stating Midtown Mobile, Downtown Mobile, and Prichard, Alabama as potentially affected areas. The tornado then weakened slightly to high-end EF1 strength, damaged several more homes, and blew out windows at Mobile Infirmary Medical Center, a hospital of more than 500 beds. Automobiles in the parking lot at the hospital were damaged, with one being flipped. It continued through the Allenville neighborhood, across I-165 and into Prichard. Damage along this segment of the path ranged from mid-range to high-end EF1, as multiple small homes and apartment buildings were damaged, some of which sustained roof loss. It also tossed several shipping containers and damaged a warehouse facility, before producing additional minor EF0 damage in the Plateau neighborhood of Prichard and then lifting. Many trees and power lines were downed along the path, which totaled . Several people suffered minor injuries. The tornado followed a path just east of the weaker EF1 December 20 tornado, which also impacted Mobile. ==Impact==

Southeast and Midwest United States In Arkansas, two people were killed in a highway accident as a result of sleet on the roads. One person was killed when high winds knocked over a tree onto a house. On December 25, more than of snow fell in Oklahoma and the Texas Panhandle. Freezing rain was blamed for a 21-car pileup on Interstate 35 near Oklahoma City. 40 Oklahoma National Guard soldiers were deployed throughout the state to assist motorists on roads. Two people were killed in separate weather-related car crashes. The driver of a truck was killed in Texas when strong winds knocked over a tree, which fell on the vehicle. The National Weather Service issued a blizzard warning for southern Illinois, the first blizzard warning in history for the region. Several counties also closed their courthouses due to the snow. Two people were killed in a traffic accident in Indiana caused by snowy roads on December 26, including an 18-year-old Ohio girl that lost control of her vehicle due to poor road conditions and crashed into a snow plow. Northeast United States and Canada A Southwest Airlines jet slid off its taxiway and got stuck in mud on the morning of December 27. There were no injuries on board, and the passengers and crew all took a later flight to their destination. A man was killed in a car accident while checking on a disabled vehicle along Interstate 78 near Allentown, Pennsylvania. On Wednesday evening, an American Airlines flight that had safely landed at Pittsburgh International Airport ran over a patch of snow on the tarmac and got stuck for approximately two hours. Nobody was injured in the incident. A record setting of snow fell over the Montreal-Laval, Quebec area. The previous record snowfall occurred 41 years earlier in March 1971 when had fallen. Numerous road accidents were reported throughout the province, including a 15-vehicle pileup near Saint-Cuthbert, Quebec. ==Aftermath==

Louisiana In Alexandria, after a relatively short-lived EF2, utility/public works crews and police and fire personnel were dispatched around the city to aid in the cleanup. Within 12 hours of the tornado hitting, nearly 100% of the power had been restored and all streets were clear of hazardous debris. In Tioga, after another EF2 tornado, neighbors, friends, and family of victims aided in the cleanup across town. Many homes and other structures were damaged and there were many volunteers ready to help victims of the tornado. Power was out in the area for at least two days. A Cenla man partnered with the American Red Cross in an effort to raise at least $10,000 for storm victims across the area. Mississippi Mississippi governor Phil Bryant declared a state of emergency for eight counties in the southern part of the state. These counties were: Pearl River, Forrest, Greene, Hinds, Jones, Lawrence, Wilkinson, and Stone. In neighboring Stone County, many people pitched in to help with the cleanup in the affected areas. Stone County was affected by the same tornado that hit McNeill. Alabama In Mobile and Prichard, volunteers distributed bottled water, yard supplies, and clean-up kits to people who were affected by the EF2 tornado in that area. Tarps were provided as well for houses that suffered roof damage. Murphy High School students were transferred to nearby Clark-Shaw Magnet School to finish out the school year as repairs were being made to Murphy High. The Salvation Army provided food for more than 1,000 people in Mobile, as well as people affected by the EF2 tornado near Troy. The Mobile Infirmary was damaged and, with no power, was relegated to using generators. Across the state, 27,600 Alabama Power customers were left without electricity, with approximately 23,000 of those in the Mobile area. A local block party and concert took place at a school in Mobile on January 4, 2013. Everything for the party, including the food, a bounce house, and the music, was donated. All proceeds went to local Catholic Social Services and the American Red Cross to be distributed to Mobile families to help rebuild after the tornado. ==See also==