Winter storm: warm temperatures mean snow faces struggle to settle

The winds are howling, and snow could fall heavily in Boston in particular, but it's probably not cold enough to really stick
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Snow in Centrerville, Virginia
Snow has accumulated in parts of Virginia, but it may have a hard time sticking in Washington and New York. Photograph: Win Mcnamee/Getty Images

Snow mixed with rain was falling in Washington on Wednesday afternoon and was expected to move up to New York City by the evening. The decision by the federal government to shut its offices down has been derided as an over-reaction – but could the storm yet live up to its billing?

Washington is expected to get perhaps a total of 1-2in. That's far less than what most forecasters, including me, thought would occur. The main issue has been that temperatures near and just above the surface have simply not been cold enough. This has caused the snow to mix with rain, and any snow that does fall has had a hard time sticking.

The weather models differed on the temperatures of the lower atmosphere in DC. The result was relatively wide ranges in snowfall forecasts, though the later model runs pointed to more, not less, snow falling. Areas to the west and south of the capital, where colder air has wrapped, such as Charlottesville and Fredericksburg, have experienced the predicted 6in of accumulation or more.

Further up the pipeline, Philadelphia's cold rain is expected to turn into snow by later this evening. But any snow will likely have difficulty accumulating because of the wet ground. I'll go with a total of 1-3in here.

New York and Boston are tougher forecasts. Models differ greatly on forecast amounts of precipitation in New York on Wednesday evening. In order to overcome the warm surface temperatures, it will have to snow quite solidly. I think about 1-3in will fall in this first wave of precipitation.

Any snow will likely to change to a drizzle at daybreak. Light precipitation should fall intermittenly on Thursday. Snow is likely in the second, heavier band of precipitiation. This norlun trough-like feature will help drag back precipitation from the departing low pressure. Again there is not much of a consensus among the models for this wave.

Will the heavier precipitation make it down to New York City? If it doesn't, the city will end up with a situation where the surface will simply be too warm for any light snow to accumulate. I think there will be some heavier rates. At this point, I'm calling for an additional 2-4in from this wave.

Total snowfall from the two waves in New York City should total 3-7in with potentially greater amounts to the east on Long Island and far north of the city in the Catskills.

Boston, along with the rest of coastal southern New England, has a winter storm watch in effect. Snow should start Wednesday night and last potentially through Friday morning.

The European weather model in particular is quite robust with precipitation amounts. Like every other major city, Boston may have to contend with warm surface temperatures. Still, I feel a pretty confident in a call of at least 6-12in of snow for most of the eastern portion of southern New England including Providence and Boston.

Coastal areas of New England and down to New York and New Jersey will also have to compete with strong winds. Gusts of up to 50mph are possible. Minor to moderate coastal flooding is possible with some beach erosion tonight into tomorrow morning around New York and Thursday morning through Friday morning in coastal New England.

Overall, it's what you might expect from a late-season winter storm. Snow is struggling to accumulate because of warm temperatures in most cities without elevation, but the winds are howling.

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