A nasty rain and snow storm known as a "bomb cyclone" came ashore late Tuesday and early Wednesday in the Pacific Northwest, knocking out power to thousands of customers and causing widespread tree damage.

South County Fire in Lynnwood, Washington, said that a large tree fell on a homeless encampment Tuesday evening, killing a woman in her 50s.

According to poweroutage.us, about 500,000 people in Washington are without electricity as of Wednesday. The power outages came as winds topped 59 mph in the Seattle area, according to the National Weather Service. Higher elevations had wind gusts of 60 to 80 mph, the National Weather Service said.

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The storm comes as the U.S. is undergoing a massive shift in weather patterns. What had been a mild November is starting to give way to a cooler, snowier weather pattern across the Midwest and Northeast. Temperatures are dropping by at least 20 degrees in much of the region as the storm system marches across the U.S.

Blizzard warnings are in place for parts of North Dakota. South Dakota and Minnesota are also expected to have some winter weather on Wednesday and Thursday.

Many parts of the Appalachians will experience their first measurable snow of the year on Thursday. Winter storm warnings, winter storm watches and winter weather advisories have been issued from Tennessee all the way north into New York.

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A bomb cyclone is defined as a storm system that rapidly intensifies, or strengthens, over a 24-hour period.

"Bombogenesis can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters," the National Ocean Service said.