While that storm will largely stay offshore, a trough axis will stretch back into New England. A trough axis is more or less a little finger of low pressure that reaches out from a storm. Troughs like this one are notorious for producing sneaky heavy snow events, particularly along the New England coastline.
In this case I expect some occasional snow showers to crop up over the area as early as Monday evening. During the pre-dawn hours of Tuesday, snow will become more steady and widespread. By Tuesday morning, including the morning commute, I expect pockets of moderate to heavy snow along the coast. Areas in Northeastern Massachusetts, Southeastern New Hampshire, and on the Outer Cape have the best chance of seeing heavy bands of snow that produce whiteout conditions.
The most challenging part of forecasting these trough snows is pinpointing exactly where those bands set up. In those affected towns, snowfall rates are likely to reach 1-4″/hour for a time. That’s why those areas are expected to pick up 6-12″. It’s a big range, but it is necessary because the focus of heaviest snow will be narrow. Keep in mind the snow that does fall will be very fluffy thanks to the return of cold air.
Elsewhere around Greater Boston expect a widespread 3-6″. That includes the city of Boston, and all of the South Shore. The closer you are to the coast, the more likely the higher end totals are. The further inland you are, the more likely the lower end totals are.
Winds will also be gusty Tuesday morning, hitting 30-40 MPH at times.
The snow will relent by about lunch-time, but travel in Eastern Massachusetts prior to that is likely to be very slow.
I’ll post more updates to the forecast as new information becomes available. Stay tuned.