Weather: Twin winter storms slam the US as 55 million travelers hit the road

Two powerful winter storms were hammering the West Coast and Midwest on Wednesday, shutting down highways and snarling travel plans on one of the nation’s busiest travel days.

Weather watches, warnings and alerts were posted across much of the western half of the nation after a storm that had been a “bomb cyclone” began its westward march from the California coast late Tuesday, AccuWeather reported.

Winter storm warnings are in effect for the mountains early Wednesday to early Friday with 6 to 12 inches of snow forecast for most mountains, except 12 to 24 inches for the San Gabriels, the National Weather Service in Los Angeles warned. “Expect significant travel delays and road closures with dangerous winter driving conditions.”

Meanwhile, parts of the central U.S. remained under siege from a storm that delayed or canceled almost 1,000 flights in Denver alone. High winds and heavy snow forced a temporary shutdown of I-70 in parts of Colorado and across the border into Kansas. It reopened in Kansas, but the state Highway Patrol urged Kansans to stay off the roads.

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“Stay put, doesn’t look like fun,” Trooper Tod Hileman warned.

As of late morning Wednesday, high winds had already knocked out power to 100,000 customers in the Midwest and Great Lakes regions, AccuWeather said.

The timing for the storms couldn’t be much worse. AAA estimates that more than 55 million travelers planned to kick off the holiday season with a trip of 50 miles or more away from home this Thanksgiving. That would be the second-highest Thanksgiving travel volume since AAA began tracking in 2000.

About 50 million of them planned to drive, and Wednesday was forecast as the heaviest driving day. Even the East was not secure, with high winds forecast that could knock down trees and power lines.

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“A powerful storm will shift from the Central Plains into the upper Midwest bringing a swath of heavy snow and damaging winds today,” the National Weather Service said in an alert Wednesday. “Strong winds shift to the Northeast on Thanksgiving, which could impact celebrations.”

The rare West Coast “bomb cyclone” swept into southern Oregon and northern California, bringing 100-mph wind gusts to the coast.

A bomb cyclone, or bombogenesis, occurs when a storm’s central barometric pressure drops at least 24 millibars in 24 hours. (A millibar is a way of measuring air pressure.) The lower the pressure, the more powerful the storm.

An all-time record low sea level pressure in the state of California was surpassed in Crescent City, California, according to NOAA’s Weather Prediction Center.

“A tale of two storms for Thanksgiving week,” the center said in summary. “The first crosses the Central Plains into the Upper Midwest into Wednesday, bringing heavy snow and strong winds. The second (spreads) heavy snow, heavy rain and strong winds across the West.”