Start of spring may bring snow to Northeast this weekend

What is a nor'easter?
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Story highlights

  • After a taste of spring, winter will make a comeback this weekend
  • A nor'easter threatens to bring snow to major cities in the Northeast
  • It's uncertain how much snow will fall

(CNN)Say bye-bye to the May-like temperatures that have warmed the East Coast.

Winter will make a harsh comeback this weekend, even though spring officially starts with the vernal equinox at 12:30 a.m. ET Sunday.
    Blame it on the nor'easter that's churning off the Atlantic coast. It's expected to deliver snow and much-lower temperatures in places like Washington, Philadelphia, New York and Boston.

    How much snow?

    As with most nor'easters, forecasting how much snow, days in advance, can prove challenging.
    We do know that a low will develop off the North Carolina coast early Sunday and move up the coast to eastern Canada by Monday. As of Friday morning, models do not agree on how far the low will be from the coast as it passes the Northeast. The location of the low will determine the amount of snow.
    If the low tracks closer to the coast, more precipitation will fall over land, making for more snow accumulation. The European model is forecasting this closer track and showing the potential for a foot of snow in eastern Massachusetts and Maine. This scenario also forecasts around 2 to 6 inches of snow from Washington to New York.
    Snow forecast from the European model
    The American Global Forecast System model says the low will be farther from the coast. This would lead to lighter snowfall and smaller snow totals, with the exception of the mid-Atlantic states. With the low so far out to sea, most of the moisture would miss the Northeast and New England, allowing only light snowfall to occur. The mid-Atlantic could still receive a couple of inches as the low pulls away from the North Carolina coast Sunday.
    Snow forecast from the American GFS model

    Cold air plunges south

    One thing is certain: Temperatures will be much lower than in previous weeks. The past week brought record-breaking temperatures near 80 degrees Fahrenheit (27 Celsius) for cities like Washington, Philadelphia, New York and Boston.
    That's about 20 degrees above average in the East. The opposite can be expected as spring arrives.
    Cold air moves into the Plains on Friday, with temperatures 10 to 20 degrees below average. Cold air will plunge all the way to the Gulf Coast, with highs struggling to reach the 60s Sunday. Morning lows below freezing will stretch as far south as Texas and the Carolinas this weekend. The Northeast can expect to become colder throughout the weekend, with afternoon highs Sunday 15 to 20 degrees below average.
    This cold blast will not remain long, with well-above-average temperatures returning Tuesday in the Plains and Wednesday in the East.

    What does this mean for the rest of spring?

    U.S. spring outlook calls for continued flood threat
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    It's not unusual to see snow after the start of spring in the Northeast.
    Just last year, New York and Philadelphia had around 4 inches on the first day of spring. Does this mean we are in for a colder than normal spring season? El Niño, though starting to weaken, continues to affect our weather patterns, and what has been a record start to the year for temperatures, not only in the United States but around the globe, will probably continue.
    The National Oceanic and Atmospheric Administration released its outlook for spring Thursday, and it calls for above-normal temperatures for the U.S. East and West coasts.