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Mother's Day weekend snowstorm could bring bomb cyclone, thundersnow to Northeast

Mother Nature wanted to make an impression this Mother's Day weekend, in what could be a once-in-a-generation May snowstorm.

Mother Nature wanted to make an impression this Mother's Day weekend, in what could be a once-in-a-generation May snowstorm poised to drop snow across portions of the Northeast and New England.

Snow will begin Friday afternoon across the interior Northeast and spread into New England by Friday evening and continue overnight, when snowfall rates could be heavy at times. This will be a heavy, wet snow, so power outages are likely (especially with leaves on the trees, which will make them heavier and easier to come down).

The big cities along the I-95 corridor will see rain, with an outside chance of some wet snowflakes mixed in late Friday night and early Saturday morning; little to no snow accumulation is expected there. Meanwhile, across the interior Northeast and New England, snowfall totals could range from a dusting to 4 inches, with locally higher amounts up to 6-8 inches and isolated totals of up to a foot. Places most likely to see the biggest snow totals include those at the highest elevations of the Adirondacks, Green and White Mountains and northern Vermont, New Hampshire and Maine.

Should flakes fly in New York City and Boston and accumulate, it would be the first time since May 1977. The record snowfall for the month of May in New York City is a trace, and 0.9 inches in Boston.

As the storm pulls away on Saturday, it will produce wind gusts of 40-60 mph across the Northeast and New England. The area of rain and snow will be off the Atlantic Coast by noon, but behind the exiting storm intense snow squalls will form off the Great Lakes and move east. These will drop visibility quickly and will likely spark thundersnow. This will be lake effect snow rare for the month of May.

The storm could intensify quickly enough over 24 hours to become a bomb cyclone by Saturday night. The definition of a bomb cyclone is a storm that drops 24 millibars in 24 hours, going through a process known as bombogenesis.

And then there's the widespread cold courtesy of the polar vortex. After not talking about the polar vortex all winter, it will take a curtain call in May. All winter, the polar vortex was extremely strong and that kept the cold air bottled up over the Arctic. Now the polar vortex has weakened, allowing a lobe of cold air to break off and dive south into the continental United States, bringing with it record-setting cold air for this time of year.

More than 100 million people are under cold alerts from the Midwest to the Mid-Atlantic, where temperatures 10-25 degrees below average will spill all the way into the Deep South. More than 70 record lows across two dozen states could be set or tied this weekend. On Saturday morning, when the cold will be most widespread, approximately 70 million people will wake up to temperatures below freezing. Wind chills in the Northeast will be in the 20s and 30s. Cities that could set record lows over the weekend include New York and Buffalo; Providence, Rhode Island; Nashville and Memphis in Tennessee; Baltimore; Detroit; Pittsburgh; Charlotte, North Carolina; Little Rock, Arkansas; Montgomery, Alabama; and Atlanta.

Atlanta could see its coldest May temperatures in 16 years. For New York City? 42 years.