‘Arctic outbreak’ forecast in some areas as millions leave

Much of the eastern US could experience a wave of severe weather as travelers hit the roads and airports for the Thanksgiving holiday.

The National Weather Service (NWS) has predicted a “major arctic outbreak” across the country, during what are often the busiest travel days of the year in the US.

Heavy snow and rain were forecast over the Colorado Rockies on Wednesday – part of a weather system that will strengthen and move east later on Thanksgiving Day. More than 10in (25cm) of snow could fall in some areas.

Temperatures are also expected to drop sharply in many areas.

An arctic blast could send temperatures as low as -30F to 40F (-34C to 40C) across the northern Plains and Upper Midwest, BBC meteorologist Matt Taylor said.

The storm is expected to move into the Midwest on Friday and the weekend, when it will also bring “lake-effect” snow and severe thunderstorms.

Lake-effect snow occurs when cold air passes over the unfrozen and relatively warm waters of the Great Lakes, causing the air to rise and form clouds that grow into a thin band that produces 2-3in of snow an hour or more, the NWS said. .

Areas that could see heavy snowfall include interior New England and the Appalachians.

In the Midwest and Great Lakes region, 4-8in of snow is possible along the northern Michigan coast, according to the NWS.

Difficult situations come at a busy travel time.

The flight disruptions began Wednesday, delaying more than 3,800 flights in the US, and 861 were canceled, according to FlightAware.

The Federal Aviation Administration said delays are possible at airports across the US, including Denver, Salt Lake City, Las Vegas, Minneapolis, Tampa Bay, Los Angeles, Dallas, Boston and Seattle. Landing delays were also experienced at Newark Liberty Airport in New Jersey due to staff shortages.

The US Transportation Security Administration (TSA) says that passenger numbers this year for Thanksgiving have already reached an all-time high.

The busiest days were expected to be the Tuesday and Wednesday, before Thanksgiving, and the Sunday after the holiday. The TSA expects to screen nearly nine million people at airports over those three days.

Meanwhile, a record number of nearly 80 million Americans are expected to drive at least 80 miles per week, according to insurance company AAA. The expected increase is due to lower gas prices than they were during the Thanksgiving holiday last year.

Thanksgiving rain and snow in the eastern US comes after a winter storm in California, on the west coast. This brought heavy snow to higher elevations earlier this week, and wind gusts as strong as 50 mph (81km/h).

Central California was hit by another “space river” event on Tuesday after experiencing a similar event last week. Weathering occurs when water evaporates from the air and is carried by the wind.

And in the Pacific Northwest, communities are still recovering from the aftermath last week’s bomb cyclonea severe weather event that occurs when air pressure drops rapidly over the coast.

The storm caused severe flooding and power outages for hundreds of thousands of people.

Those affected areas could face even more wet weather this week, as the NWS predicts a low pressure system will bring coastal rain to Washington, Oregon and California.