Uncertainty about the exact storm track and how cold it will be means there is less confidence in how much snow will accumulate near I-95. Precipitation totals — rain and snowmelt — will range from about 0.75 to 1.25 inches across the Mid-Atlantic and Northeast.
The sweet spot for snow accumulation could stretch from central Pennsylvania to Massachusetts, where 6 to 12 inches could fall between Monday night and Tuesday. Vulnerable population centers include State College and Scranton in Pennsylvania; Poughkeepsie, NY; Hartford; Providence; and Springfield and Worcester in Massachusetts. Because it's a heavy, wet snow — especially at lower elevations — there's a risk of tree limbs and power outages.
However, with the storm still three days away, a zone of heavy snowfall could change. Some models suggest that the Snow Jackpot Zone may focus north from inland New York (including Albany) through Vermont and New Hampshire and into southern Maine. Under these conditions, less snow will fall from central Pennsylvania to Rhode Island and southern Massachusetts.
The storm will bring an unusually mild weekend to the Mid-Atlantic and Northeast, with temperatures forecast to reach the 50s and 60s in some areas. Unusually warm weather has swept much of the nation this week, and as of Friday morning, snow covered only 27.6 percent of the contiguous U.S. — one of the three lowest percentages on record for the date.
Why is the snow forecast so uncertain near I-95?
On Sunday and Monday, cold air will move towards the northeast. But temperatures on Monday should reach the 40s to 50s along the I-95 corridor. The main ingredient for significant snow on I-95 is an area of high pressure north of Canada that will push freezing air southward. But this storm lacked that ingredient.
By Tuesday morning, temperatures from New York City to Boston should drop to at least the mid-30s. But whether they fall to the right or below freezing depends on the exact track of the storm and how heavy the precipitation is. More precipitation will cool the lower atmosphere by a few degrees, increasing the odds of significant snow accumulation.
The National Weather Service office, which serves the New York City area, summarized the forecast uncertainty: “Small north-south changes in the low track will determine where the rain-snow line sets and how quickly coastal locations will turn to snow.”
Sunday to Monday: The storm begins late Sunday into Monday with heavy rain across 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 has highlighted the risk of severe thunderstorms on both days along the Gulf Coast, affecting New Orleans and Birmingham on Sunday and advancing to Tallahassee, Atlanta and Jacksonville on Monday.
Starting from Monday to Tuesday: Rain will spread north into Virginia on Monday, followed by rain, snow and gusty winds across Maryland, DC, West Virginia, Delaware, southern Pennsylvania and southern New Jersey Monday evening into early Tuesday morning.
Monday evening to Tuesday: A mix of rain, sleet, snow and strong winds will move through the Northeast and coastal New England Monday night and Tuesday, with heavy snow falling inland. Precipitation should move offshore by Tuesday evening, with onshore winds through Wednesday.
Forecast for the I-95 Corridor
Rain will arrive on Monday night, possibly in the wee hours of midnight, and will change to mostly snow moving north and west of the city on Tuesday morning. Even a little drizzle can mix.
Initial estimates call for between half an inch and 3 inches of snow in the city. But scenarios with more snow, perhaps 3 to 6 inches or less, are mixed with more rain. Chances of 3 inches or more are 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 there is uncertainty about how heavy the snow will be and how cold it will be. Winds could reach 30 to 40 mph around the city and 40 to 50 mph on Long Island Tuesday and Tuesday night.
Rain will develop early Tuesday morning, probably after 2 a.m., before clearing Tuesday evening as temperatures drop to near or below freezing, turning to mostly or all snow by sunrise. Even a little drizzle can mix.
The first guess is 3 to 7 inches of snow. But forecast confidence is low due to uncertainty in the precise storm track and is subject to significant change. So a little more snow than that is possible, and less rain.
Wind gusts of 30 to 40 mph around Boston and 40 to 55 mph on Cape Cod are possible Tuesday through Wednesday. Minor to moderate coastal flooding is a concern in eastern Massachusetts, where the weather service predicts a rise of 1.5 to 2.5 feet during high tide.
Rain should start Monday evening, perhaps around 10 p.m., mixing with snow and sleet on Tuesday, tapering off by noon.
It looks like above-freezing temperatures will reduce snow potential to an inch or less, with the best chance for snow accumulation in grassy areas north of the city. But small changes in the storm track could make the forecast a bit snowier.
Winds will be 25 to 35 mph Tuesday and Tuesday night.
Rain should fall Monday afternoon into the evening, heavy at times Monday night, and possibly Tuesday morning, especially north and northwest of cities, with some snow or sleet mixing with snow by late afternoon.
Temperatures should remain above freezing throughout the storm, with a chance of light snow accumulations, mainly in grassy areas north and northwest of the Washington and Baltimore Beltway. Winds up to 35 mph are possible Tuesday through Wednesday.
Interior and mountain snow
Central and northeastern Pennsylvania, the Hudson Valley, Connecticut, parts of Rhode Island, central and western Massachusetts, and far southern New Hampshire and Vermont could get about 6 to 12 inches of snow. Higher elevations may have higher levels as it may not be cold enough to sustain snow. Parts of western Maryland and West Virginia could get about 3 to 6 inches less.
With the storm still a few days away, there is still room for fluctuating snowfall.
Jason Samenow contributed to this report.