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Spokane, Washington  Est. May 19, 1883

Big storm to dump heavy rain, snow along East Coast in coming days

Snow covers the White House grounds Jan. 19 in Washington, D.C.  (Drew Angerer)
By Dan Stillman Washington Post

A sprawling winter storm known as a nor’easter is expected to bring significant weather and travel impacts to the Mid-Atlantic and Northeast on Monday and into Tuesday, after first dumping heavy rain and causing possible severe thunderstorms along the Gulf Coast and in the Southeast on Sunday and Monday.

The storm is likely to produce plowable snow across interior and mountain regions of the Mid-Atlantic and Northeast. Closer to the coast, along the Interstate 95 corridor, a mix of rain and snow is probable from New York City to Boston.

Confidence remains low regarding how much snow will accumulate near I-95 because of uncertainty about the exact storm track and how cold it will get. Total precipitation – rain plus melted snow – across much of the Mid-Atlantic and Northeast looks to be in the range of about 0.75 to 1.25 inches.

The sweet spot for accumulating snow may stretch from central Pennsylvania into Massachusetts, where 6 to 12 inches could fall between Monday night and Tuesday. Population centers that could be affected include State College and Scranton in Pennsylvania; Poughkeepsie, N.Y.; Hartford; Providence; and Springfield and Worcester in Massachusetts. Because it will be a heavy, wet snow – especially at low elevations – there will be a risk of damage to tree limbs and power outages.

However, with the storm still three days away, the predicted zone of heaviest snowfall could shift. Some models suggest that the snow jackpot zone could be focused farther north, from interior New York (including Albany) through Vermont and New Hampshire and into southern Maine. In this scenario, less snow would fall from central Pennsylvania into Rhode Island and southern Massachusetts.

The storm will follow an unusually mild weekend in the Mid-Atlantic and Northeast, and even record-breaking warmth in some areas, where temperatures are forecast to reach the 50s and 60s. Abnormal warmth has swept through much of the nation this week while, as of Friday morning, snow covered only 27.6 percent of the contiguous United States – among the three lowest percentages on record for the date.

Cooler air moves into the Northeast on Sunday and Monday. But temperatures on Monday should still reach the 40s to near 50 along the I-95 corridor. A key ingredient for significant snow along I-95 is a zone of high pressure to the north over Canada that would funnel freezing air southward. But that ingredient is absent for this storm.

By Tuesday morning, temperatures should dip at least to the mid-30s from New York City to Boston. But whether they drop to right around or just below freezing depends on the precise track of the storm and how heavy the precipitation is. Heavy precipitation can chill the lower atmosphere by a few degrees, increasing the odds of more significant snow accumulation.

The National Weather Service office serving the New York City region summarized the forecast uncertainty: “The slightest north-south shifts in the low track will determine where the rain-snow line sets up and how quickly coastal locations will go over to snow.”

General storm timeline

Sunday into Monday: The storm gets started with heavy rain late Sunday into Monday across portions of the Southeast, where 1 to 3 inches of rain could fall from the Florida Panhandle northward through Alabama, Georgia and the Carolinas. The Weather Service’s Storm Prediction Center is highlighting an elevated risk for severe thunderstorms along the Gulf Coast both days, affecting New Orleans and Birmingham on Sunday and progressing to Tallahassee, Atlanta and Jacksonville on Monday.

Monday into early Tuesday: The rain spreads northward into Virginia on Monday, followed by rain, mountain snow and gusty breezes in Maryland, D.C., West Virginia, Delaware, southern Pennsylvania and southern New Jersey on Monday evening into early Tuesday.

Monday evening into Tuesday: A mix of rain, snow, sleet and strong winds sweeps through coastal areas of the Northeast and New England on Monday night and Tuesday, while heavy snow falls in the interior. The precipitation should head out to sea by Tuesday evening, with gusty coastal winds lingering into Wednesday.

Forecast for I-95 corridor

New York City: Rain should arrive Monday night, perhaps within a few hours of midnight, and could become mostly snow from the city toward points north and west Tuesday morning before tapering in the afternoon. A little sleet could mix in as well.

A first guess is around a half-inch to 3 inches of snow in the city. But scenarios with more snow, perhaps as much as 3 to 6 inches, or less snow mixed with more rain, are still possible. The best chance of 3 inches or more is north and west of the city, while Long Island is likely to see less than an inch of snow or mostly rain.

Forecast confidence is low and thus subject to significant change, because of uncertainty in how heavy the snow will be and how cold it will get. Winds on Tuesday and Tuesday night could gust 30 to 40 mph around the city and 40 to 50 mph on Long Island.

Boston: Rain should arrive early Tuesday, probably after 2 a.m., potentially becoming mostly or all snow by around sunrise as temperatures drop to near or below the freezing mark, before moving out Tuesday evening. A little sleet could mix in as well.

A first guess is around 3 to 7 inches of snow. But forecast confidence is low and thus subject to significant change, because of uncertainty in the exact storm track. So a little more snow than that is possible, as is less with more rain mixed in.

Winds could gust 30 to 40 mph Tuesday into Wednesday around Boston, and 40 to 55 mph on Cape Cod. Minor to moderate coastal flooding is a concern in eastern Massachusetts, where the Weather Service is predicting a surge of 1.5 to 2.5 feet at the time of high tide.

Philadelphia: Rain should develop Monday evening, perhaps around 10 p.m., possibly mixing with snow and maybe sleet on Tuesday before tapering by midday.

It looks like temperatures will remain above freezing, which should limit snow potential to around one inch or less, with the best chance of accumulating snow on grassy areas north of the city. But small changes in the storm track could change the forecast to a slightly snowier one.

Winds on Tuesday and Tuesday night could gust 25 to 35 mph.

Washington, Baltimore: Rain should develop Monday afternoon into the evening and could be heavy at times Monday night, perhaps mixing with a little snow or sleet Tuesday morning, especially north and northwest of the cities, before tapering by midday.

Temperatures should remain above freezing throughout the storm, with only a chance of a light snow accumulation, mainly on grassy areas north and northwest of the Washington and Baltimore beltways. Winds could gust near 35 mph Tuesday into Wednesday.

Interior and mountain snow

Interior snowfall could range from around 6 to 12 inches across much of central and northeast Pennsylvania, the Hudson Valley, Connecticut, parts of Rhode Island, central and western Massachusetts, and far southern New Hampshire and Vermont. Because it will be barely cold enough to support snow, heaviest amounts are probable in the higher elevations. Lesser amounts, around 3 to 6 inches, are probable for Western Maryland and portions of West Virginia.

There is still wiggle room for those snow totals to fluctuate given that the storm is a few days out.

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Jason Samenow contributed to this report.