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A frightful arctic blast thwacked the eastern half of the U.S. just in time for Halloween, bringing the first deep freeze of the season for many areas after an unseasonably warm week. Highs Saturday are expected to be 10 to 20 degrees below average from the Mississippi Valley to the East Coast, according The Weather Channel.

The flurry of frosty air whipped the northern Plains on Thursday, with the front blowing across the Great Lakes and setting off the season's first lake-effect snow in the upper Midwest. As much as 4 inches of snow was forecast beginning Thursday night for northern Wisconsin and the Upper Peninsula of Michigan, spreading as far south as northern Indiana on Friday.

The chill will move through the East by the weekend, forecasters said. Areas of the country that enjoyed record highs Monday and Tuesday — including Savannah, Georgia, and Rochester, New York — will see temperatures "plummet" by the weekend, according to The Weather Channel.

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Winter storm watches were issued beginning Friday night for 11 counties in North Carolina and for higher elevations in parts of in Virginia, with 2 to 4 inches of snow forecast over southwest Virginia and northeast Tennessee. More than 6 inches is likely in higher elevations of Tennessee and North Carolina, the National Weather Service said.

January-like temperatures will even extend as far south as Florida, with the low Sunday in Orlando expected to drop into the mid-40s — challenging the city's Nov. 2 record of 46, set in 1993.

Meanwhile, city officials who began stockpiling salt this week in Penfield, New York, got a nasty Halloween fright: Supplies are short after last year's brutal winter, meaning prices are way up.

"Last year, our price was approximately $36.40 [a pound], and this year we're looking at $43.67," Town Supervisor Tony LaFountain told NBC station WHEC of Rochester, New York. "So around now, it's about a 20 percent increase."

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Forecasters predict cold air & potential snow for New England this Halloween. Here, we trick or treat on flip-flops. pic.twitter.com/mUoeoo8Oky — Puerto Rico Tourism (@PRTourismCo) October 30, 2014

Ready for an Arctic blast?! Check out these wind chills for Sunday morning! Complete forecast: http://t.co/0rlUrWwvaw pic.twitter.com/WDKC172xS9 -The Weather Channel (@weatherchannel) October 29, 2014

— Cassandra Vinograd and M. Alex Johnson