The snowstorm arrived in the wee hours of the morning across Greater Boston and will continue to spread off towards the north. Cold, dry air in Northern New England will prevent snow from penetrating quickly north and west, but everyone will get in on some of the action eventually.
Think of this as a general 1- to 2- feet kind of storm for everybody, from roughly Worcester eastward. When it comes to higher snow totals however, there will be a sharp cutoff. This cutoff could be further east and south as the storm moves north towards Nova Scotia later Saturday.
The heaviest snowfall totals are likely to be from Boston back through Metro West, along with southeastern cities and towns. Storms like this produce what meteorologists call mesoscale banding. These bands of heavy snow rotate around the storm and are basically enhanced areas of lifting that create very heavy snow. The snow underneath these bands can accumulate at 1 to 3 inches per hour, but on the outside of the band, snow can actually be much lighter. That’s why you end up seeing areas with a lot of snow fairly close to areas with far less of it. Because of this, the final snowfall maps after the storm can look quite different from the predicted ones before it.
As you look out the window today, you’re likely to see it snowing hard at times and then lightening up at others.
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When the storm began, temperatures were actually above freezing across Cape Cod and the Islands which meant some rain, but the colder air will continue to push towards the coastline. Although the snow will at first be heavy and wet in that part of the state, it will lighten up throughout the morning and into the afternoon.
Most of the snow will have fallen by 5 p.m. to 7 p.m. with the final flakes between 7 p.m. and 10 p.m. from west to east. I put together a composite of predicted snowfall rates through the evening. This is just a computer’s idea of how the storm will play out, but you get the idea. Notice the darker purple areas, which is where the heaviest snow is situated. These rotate east and offshore this evening.
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Coastal flooding does not look like a problem beyond some minor occurrences. The chart below of tides in Scituate gives you an idea of how much above normal the water will go -- it is certainly not significant when compared to other winter storms. Harbors throughout the region have similar forecasts for minor flooding.
The blizzard warning will remain in effect the entire day. This is because visibility is forecast to be a quarter-mile or less for three hours in a row due to the blowing snow and intense wind. The wind is caused by the low pressure and tight gradient. The black lines on the map below represent isobars where the pressure is the same. When you have a lot of these in a short distance, you have a lot of wind.
The cold is the other big factor with this storm. Temperatures will be falling throughout the day and into overnight with wind chill values below zero. This will make it uncomfortable to clean up, although it does mean the snow will continue to be quite light in texture.
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Sunshine returns for Sunday with temperatures in the 20s. The snow melt will begin on Tuesday and last into Friday. It won’t all disappear, but it will be notably less by then.