A powerful storm may sock southern New England, including Boston, with more than 14 inches (36 centimeters) of snow later this week and 6 inches or more in New York City.
Revised estimates indicate as much as 18 inches of snow may cover Boston and central Massachusetts by 7 p.m. on Feb. 9, the National Weather Service said. Earlier, 8 to 10 inches were predicted for Boston.
Those totals may go up, Rob Carolan, a meteorologist and founder of Hometown Forecast Services Inc. in Nashua, New Hampshire, said by telephone.
“It has the potential to be a big one,” Carolan said.
The weather service posted a winter storm watch from Maine to Connecticut. A hazardous weather alert is in effect from New York City to Cape Cod. Snow may begin falling in New York tomorrow night and then spread into New England early Feb. 8.
“We have come to the consensus that eastern New England will be experiencing blizzard conditions late Friday into Saturday morning,” said Paul Walker, an expert senior meteorologist with AccuWeather Inc. in State College, Pennsylvania.
Large amounts of snow will depend on the near-perfect timing of an influx of cold air mixing with moisture coming up from the South, Carolan said. Most computer models don’t see that happening yet, although one used by the European Center for Medium-range Weather Forecasts does.
Commonly known as “the European model,” it predicts all the components will come together as the storm passes Long Island and Cape Cod, which may mean 2 feet of snow in Boston and a foot in New York City, he said.
“The European model has been on it, off and on, for over a week,” Carolan said. “When the European forecasts a historic storm, it usually happens. We have a saying around here: ‘You ignore the Euro at your peril.’”
The model accurately predicted Hurricane Sandy’s unusual westward turn into the U.S. East Coast in October.
Carolan said other forecasting models don’t expect the same large snowfall because they don’t see the pieces of the storm coming together as perfectly. If those models are right, the system won’t get the dose of cold air it needs to bring hours of heavy snowfall to New England and New York.
“The other models are keeping the best moisture offshore, so it’s a snowstorm but it’s not a historic snowstorm,” Carolan said.
The lack of agreement between the forecasting models makes predictions complicated, said Tim Morrin, a weather service meteorologist in Upton, New York. On the low end, New York may receive about 2 inches of snow to cap off a day of cold rain on Feb. 8, Morrin said.
“The computer models are spread out and that doesn’t lend a lot of confidence,” Morrin said. “I think the timing is pretty confident, but the type of precipitation and the amount is a little sketchy. The folks should prepare for a little snow.”
Also complicating matters is that some of the energy that will drive the event is still off the West Coast, Walker said.
South of New York City, the storm is expected to be mainly rain. There is an 80 percent chance of rain in Philadelphia and Trenton, New Jersey, for Feb. 8, the weather service said.
One component of the possible storm is spreading 5 to 6 inches of snow over eastern Wisconsin today, according to the agency. A winter storm warning and advisory extend along the Wisconsin coastline of Lake Michigan.
Another part is bringing rain and thunderstorms to Texas and Louisiana.
Snow has been relatively rare in the Northeast this season. Since Oct. 1, 7.4 inches have fallen in New York’s Central Park, 6.4 inches fewer than normal.
In Boston, 9.6 inches have fallen since Dec. 1, 14.3 inches below normal, according to the weather service.
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