Tens of millions of Americans are bracing for a massive winter storm Sunday, which is forecast to bring the heaviest snowfall and coldest temperatures to parts of the country in over a decade. The polar vortex has already prompted states of emergency in the Plains,

As a deep winter chill begins to take over the northern half of the country, a new major winter storm will move across the U.S. this weekend into early next week.

The polar vortex — ultra-cold air spinning like a top — usually stays above the North Pole, but sometimes stretches down to the U.S., Europe or Asia, causing intense doses of cold.

Up to 30cm of snowfall is expected in some areas as the Met Office warned of rare freezing rain across England and Wales