Late December 2012 North American storm complex

Meteorological synopsis

On December 24, the Storm Prediction Center (SPC) issued a moderate risk for severe storms, valid for the following day. 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, a strong upper-level trough moved southeast into Texas from the Rocky Mountains on the evening of the 24th, 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. Initially, the convection congealed into a quasi-linear convective system while over northeast Texas and western Louisiana, with only a few tornadoes touching down in these areas. Later in the afternoon, enough energy associated with the advancing shortwave trough allowed for the formation of tornadic supercell thunderstorms ahead of the advancing squall line in Louisiana, southern Mississippi, and southern Alabama. Southerly winds near the surface increased, providing strong low level and deep layer wind shear needed for these supercell thunderstorms. Many of the supercells would go on to produce tornadoes. By late in the evening, most storms had congealed into a squall line and weakened due to waning instability.

In the early hours 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 987 mb (29.15 inHg). 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 system, just east of the United Kingdom.

McNeill/Maxie, Mississippi area

This EF3 tornado touched down southwest of McNeill and snapped several trees. It then rapidly intensified and destroyed a single-story brick triplex, with only two interior walls left standing. One house in McNeill that was destroyed had survived effects from both Hurricane Camille and Hurricane Katrina. It then crossed U.S. Route 11 and weakened, producing minor roof damage and downing several trees. It also crossed Interstate 59 and travelled through mostly rural areas southeast of Poplarville before reintensifying and crossing into Stone County. In Pearl River County, 22 homes were destroyed, eight had major damage, 16 had minor damage, and an additional nine were affected in some way. Eight people were injured in Pearl River County as it tracked for about 24 miles (39 km). The tornado entered Stone County west of Texas and caused significant damage to a few homes. It then snapped numerous pine trees and destroyed a manufactured home. Another manufactured home was rolled into a frame house and several more trees were downed before the tornado moved out of Stone County. Damage in Stone County was rated EF2 as it tracked for 8 miles (13 km).

The tornado then moved into Forrest County where numerous trees and power lines were downed. Two double-wide homes were destroyed, a pickup truck was rolled, and a camper was thrown about 50 yards (46 m). Two additional double-wide homes were nearly destroyed, a single-wide mobile home sustained major damage, and a tree demolished a travel trailer. Four people were injured in Forrest County. Damage in this county was rated EF2 as the tornado traveled for 6.9 miles (11.1 km).

The tornado crossed into Perry County near the DeSoto National Forest at EF1 strength. It quickly regained EF2 status and downed electrical transmission lines. The tornado then destroyed a manufactured 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 20 miles (32 km). The tornado then crossed into Greene County near McLain as an EF1 and caused roof damage to an elementary school and a few homes. It also downed several trees before lifing after a path length of 1.4 miles (2.3 km). The tornado tracked for 60.4 miles (97.2 km) across five counties and injured 12 people.

Mobile, Alabama

This large wedge tornado was caught on television tower cameras as it moved through Mobile. The tornado initially touched down at 2254 UTC (4:54 p.m. CST) along Dauphin Island Parkway, just northwest of Interstate 10 and produced damage consistent with an EF1 tornado. Several commercial retailers and numerous homes were damaged, including loss of roof at many of these structures. Several outbuildings were destroyed, numerous structures had windows blown out, and Murphy High School sustained significant damage. Damage at the high school included six portable classrooms being levelled, the roofs being torn off of the auditorium and band building, and other roofs on the school being lifted off the building, only to be deposited back onto the building. The tornado continued northward and strengthened, producing EF2-strength 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. The tornado widened to its widest point of 200 yards (180 m) in this area.

The tornado then weakened slightly (to high-end EF1/weak EF2), damaged several more homes, and blew 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 across Interstate 165 and into Prichard, where it produced roof damage to several homes. It also tossed several shipping containers and damaged a warehouse facility before it lifted. Many trees and power lines were downed along the path, which totaled 5.7 miles (9.2 km). Several people suffered minor injuries. Damage estimates to the cities of Mobile and Prichard totaled out at $1.35 million.

A tornado emergency was issued for the tornado as it approached areas of Downtown Mobile at 2300 UTC (5:00 p.m. CST), stating Midtown Mobile, Downtown Mobile, and Prichard, Alabama as potentially affected areas. The tornado followed a path just east of the weaker December 20 tornado, which also impacted Mobile.

Southeast and Midwest United States

In Arkansas, two people were killed in a highway accident as a result of sleet on the roads. A Louisiana man was killed when high winds knocked over a tree onto a house. On December 25, more than 6 inches (15 cm) 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. Two people were killed in separate weather-related automobile accidents in Virginia.

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, and an 18-year-old Ohio girl was killed when she 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.

Over 200 flights were cancelled at Toronto Pearson International Airport. Several pedestrian and car accidents were reported. A record setting 18 inches (46 cm) of snow fell over the Montreal-Laval, Quebec area. The previous record snowfall occurred 41 years earlier in March 1971 when 42 centimetres (17 in) had fallen. Numerous road accidents were reported throughout the province, including a 15-vehicle pileup near Saint-Cuthbert, Quebec.

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.

Many donations were brought to the McNeill, Mississippi VFD building for victims of the EF3 tornado in Pearl River County. These donations came from citizens and businesses of many surrounding areas, such as Gulfport, Mississippi and Slidell, Louisiana. Items such as toiletries and yard supplies (shovels, rakes, etc.) were provided by the Sam's Club and Tractor Supply stores in Slidell. Many articles of clothing as well as many other supplies were donated as well. 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.