The January 4–8, 2017 North American winter storm was a major snow and ice storm that affected the Lower 48 of the United States with winter weather. Moving ashore on the West Coast on January 3, the system produced heavy snowfall in the Sierra Mountains, with nearly 4 feet of snowfall falling in the highest elevations. After impacting the Northwest and Southwest, the winter storm went on to strike the Southeast on January 5–6 with snow and ice, with snowfall accumulations up to . Afterwards, it began to morph into a nor'easter as it moved off the Southeast coast late on January 6, while producing blizzard conditions in the Carolinas. It then began to affect the Northeastern United States as it tracked northwards early on January 7. It produced a swath of moderate snowfall accumulations up the East Coast, with easternmost areas such as parts of Massachusetts receiving up to of snow.
Fearful of another disaster reminiscent of that from late January 2014, residents of states such as Louisiana, Mississippi, Alabama, and Georgia prepared in advance for the storm. Multiple advisories were issued in advance for winter weather in the affected areas. The storm caused nearly 35,000 or more power outages in the south, with at least six fatalities confirmed.
Meteorological history
On January 4 around 00:00 UTC, an area of low pressure associated with an atmospheric river moved onshore on the West Coast of the United States. With cold air in place, heavy snow began to fall in parts of Montana, Oregon, and in the Sierra Mountains, with maximum accumulations of nearly 4 feet. As it dived southeastwards, the low dissipated because of interaction with the mountains of areas such as Arizona, New Mexico, and Nevada. However, leftover energy from the dissipating system continued to move south towards the Southeast.
At the same time, a stationary front formed within the northeastern part of the Gulf of Mexico, and once this energy reached the front with cold air in place, snow, sleet, and ice began to break out in areas such as Louisiana, Mississippi, Arkansas, and Alabama as a new area of low pressure formed along the stationary front late on January 5. The aforementioned low then quickly moved onshore and continued to produce more wintry precipitation, as it tracked eastwards throughout the day on January 6. By 06:00 UTC on January 7, a new low developed just offshore the South Carolina coastline, and this low eventually became the dormant low as the system tracked offshore.
The winter storm then began to intensify as it began tracking north-northeast, hugging the East Coast of the United States, while transitioning into a nor'easter. As it did so, snowfall began to spread all into parts of the Northeast, including New Jersey, New York, and Connecticut during the course of January 7. Further deepening of the winter storm occurred as snowfall began to end in parts of New England, and by 15:00 UTC on January 8, the cyclone had finally moved away from the coastline as an arctic airmass of high pressure began to settle in behind the storm. For the next two days, the storm system moved through Atlantic Canada and Southern Greenland, before being absorbed by a frontal system, forming to the west of Iceland on January 13.
Preparations and impact
Southeast
On January 6, 2017, North Carolina Governor Roy Cooper declared a state of emergency. 10 inches of snow fell in Greensboro, High Point, Lewisville and Lenoir, and at one point 25,000 were without power. 700 traffic accidents were reported.
The winter storm laid a thin layer of ice across parts of the state of Mississippi, causing multiple road closures. Portions of Interstate 20 and Interstate 55 were also closed because of the ice, as multiple bridges and overpasses had ice on them. 62 accidents were reported, but there were no injuries reported from the Magnolia State.
In Alabama, governor Robert J. Bentley declared a state of emergency on January 5, in advance of the storm, deploying 300 soldiers of the Alabama National Guard for assistance. Roads were closed in Alabama as the winter storm moved through, with officials urging residents to stay inside. Multiple portions of interstates were closed, with the climax being Interstate 59 becoming impassable early on January 8. Curfews were also put in place as conditions deteriorated quickly, advising travel would not be a good idea.
Early on January 7, travel was nearly impassable in the northern portion of Georgia, with 10,000 customers reporting power outages. 700 flights were cancelled at the Hartsfield-Jackson International Airport on January 6–7. Multiple cars were also reported to have slid off roads because of the treacherous conditions.