Draft:December 2018 North American storm complex

A flood event and winter storm, with the latter unofficially named Winter Storm Diego by The Weather Channel and nicknamed "Snowmageddon 2018", impacted portions of the Western, Southern, and Mid-Atlantic in December 2018.

California
The storm system first impacted the state on December 6, producing heavy rainfall across lower-level elevations and heavy snowfall across high elevations and mountainous areas. Heavy rainfall forced a mandatory evacuation for the Holy Fire burn scar in Orange and Riverside counties, and also prompted a flash flood warning for the burn scar area. Several other burn scar areas also received heavy rainfall, including the Woolsey Fire burn scar area. Mudslides and debris flows forced numerous roads to close, including the Pacific Coast Highway and California State Route 170, and heavy rainfall and flooding forced several schools to close early, including Corona del Mar High School. A Southwest Airlines flight slid off a runway at Hollywood Burbank Airport, as the airport itself was under a ground stop, and all Southwest operations at the airport were suspended after the incident. A 13-car crash near Moreno Valley caused one minor injury and forced all westbound lanes of California State Route 60 to close, while a six-car crash on California State Route 91 in Corona injured one person. In Los Angeles, 1.9 in of rain fell, which set a new rainfall record in the city, breaking the previous record set in 1997. There were 119 vehicle crashes across Los Angeles County on December 6. One person was killed after a vehicle accident on Interstate 5 in Burbank. Heavy snowfall forced the closure of Interstate 5 between Los Angeles and the San Joaquin Valley, and almost two dozen commercial trucks were stranded and towed on Interstate 5.

Texas
On December 8, Lubbock received 10 in of snow, which set a daily snowfall record.

North Carolina
Before the winter storm, governor Roy Cooper issued a state of emergency, and numerous schools were closed, including classes being cancelled at Duke University. Near Winston-Salem, over 16 inches of snow fell, and in Busick, 34 in of snow fell. Daily records were set in Raleigh, Greensboro, Asheville, and Charlotte, North Carolina, with the latter two locations receiving 5.3 in and 2.7 in of snow, respectively. The highest snowfall accumulation in North Carolina was recorded in Saluda, where 18.5 in of snow fell. Additionally, in Greensboro, 12 in of snow fell, which was recorded as the second-highest snowfall accumulation on record in December and the third-highest snowfall accumulation on record. At Raleigh–Durham International Airport, 7 in of snow fell, which was recorded as the highest snowfall accumulation there in nearly 17 years. After the December 10 snowfall event, snow did not fall at the Piedmont Triad International Airport for 436 days, which was recorded as the fifth-longest period without measured snowfall. Also at the airport, at least 2 in of snow did not fall there until 1,134 days after the snowfall on December 10. Additionally, snow did not fall in Charlotte for more than three years after the December 10 snowfall. More than 1,100 flights were cancelled at Charlotte Douglas International Airport. There were three fatalities and nearly 200,000 power outages across the state.

Virginia
In Roanoke, Virginia, 15.2 in of snow fell on December 9, which was recorded as the highest daily snow accumulation on record. Additionally, the snowfall in Roanoke, Blacksburg, and Danville on December 9 were recorded as the highest snowfall accumulations in a day in the month of December. Appalachian Power had 20,000 without power in Virginia.

Elsewhere
Prior to the winter storm, Oklahoma governor Mary Fallin declared a state of emergency for all 77 counties in the state, and the state's emergency operations center was activated. The storm caused icing across Tennessee and Arkansas as well as some snowfall. Late on December 9, 1 ft of snow or more had fallen in parts of North Carolina and Virginia; both states had declared states of emergency. 240,000 Duke Energy customers had lost power in North Carolina, along with 170,000 more in South Carolina. Alabama, Georgia and Tennessee also had power outages.

In Tennessee, the heaviest snowfall occurred across northeastern portions of the state. Across the Tri-Cities area, 10 in of snow fell at Tri-Cities Regional Airport with 9.4 in of it accumulating on December 9, which was recorded as the highest accumulation in a day in the month of December. The winter storm was also ranked as the most impactful in 25 years across the Tri-Cities region, and the heaviest snow in the state fell east of Gray, where 11.5 in of snow fell.