A powerful winter storm has caused chaos across the Plains and parts of the Midwest, with blizzard conditions and heavy snowfall leading to numerous weather-related incidents. The National Weather Service has issued winter weather alerts for seven million people, warning of potentially damaging ice and dangerous travel conditions. The storm is expected to last until Wednesday in the north-central part of the US.

Snow has been falling at a rate of an inch an hour in several areas including northeast Colorado, western South Dakota, western Nebraska, and northwest Kansas. Over the past 48 hours, significant snow accumulations have been reported, with Douglas Pass, Colorado receiving 13 inches, Lander, Wyoming receiving 11.4 inches, Columbus, Nebraska receiving 8 inches, and the Denver metro area receiving 1 to 3 inches.

Icy roads have caused over 100 weather-related incidents in Nebraska, mainly slide-offs and non-injury situations. Images from the chaos show jackknifed semitrucks and tractor-trailers that have veered off roads. South Dakota has also been heavily affected, with the Transportation Department warning of "zero visibility" conditions on roads and closing Interstate 90. A blizzard warning is in effect until early Wednesday morning, affecting around 600,000 people across five states, particularly South Dakota and Nebraska. Additional snow accumulations of 2 to 7 inches and wind gusts of up to 60 mph are expected.

The winter storm is part of a larger system that is causing rain and storms in the mid-Atlantic and Southeast, as well as strong winds in certain areas. This combination of weather conditions is expected to disrupt post-Christmas travel, with delays likely at major airports such as Denver, Minneapolis, Cleveland, and Charlotte. Southwest Airlines has already canceled hundreds of flights due to thick fog at Midway Airport in Chicago. On Tuesday, over 1,700 flights within, to, or out of the US have been delayed, and 50 have been canceled.

The storm system will continue to affect the Northeast on Wednesday, bringing rain and potential travel delays to major hubs including Washington, D.C., New York, and Boston. The forecast predicts rainfall of 0.5 to 2 inches, with isolated flash flooding possible in certain areas. Dense fog is also causing low visibility and dangerous driving conditions, particularly in New York, Hartford, and Boston. A dense fog advisory has been issued for the Northeast, affecting 37 million people.

One million people in the northern Great Plains were under a blizzard warning on Monday, with heavy snowfall and powerful winds expected to disrupt travel and create treacherous road conditions. Central South Dakota, where over a foot of snow was possible, was likely to experience the worst of the storm. Parts of South Dakota were forecasted to receive up to 13 inches of snow, accompanied by wind gusts up to 55 mph. The South Dakota Department of Transportation had to close parts of Interstate 90 due to near zero visibility caused by blowing snow.

The storm also caused an accident involving several jackknifed tractor-trailers on Interstate 80 in Nebraska. No injuries were reported, but slick road conditions and blowing snow were contributing factors. Power outages were also a concern, particularly in South Dakota, as strong winds could damage trees and power lines. The heaviest snowfall in central South Dakota was expected in the afternoon and evening, with snow and strong winds persisting into the night. A blizzard warning was in effect until late Tuesday night.

The effects of the storm were felt in Colorado and Kansas as well, with freezing rain causing slick conditions and up to eight inches of snow and wind gusts of up to 60 mph possible. Travelers planning to hit the road on Monday were urged to reconsider, as conditions were expected to worsen. However, temperatures were set to rise in certain areas, improving driving conditions and reducing the impact of falling snow. Despite some flight cancellations and delays, the impact on air travel was relatively minor at the start of the storm. Travelers were advised to check with their airlines for any changes to their flights.