It's just a matter of degree, and that's what's uncommon.
There are three key factors that will add or take away a foot or more of possible snow in southeastern New England.
1. How close to the coast or how far south arctic high pressure pushes the core of the storm.
There's a sweet spot about 100-150 miles off the south/southeast coast of Massachusetts. If the storm tracks north or west of it, the south coast and major cities get mainly rain. If it's tracked much further south or east of this area, it will all be snow, but only light amounts. I'm thinking that the storm will track just off the coast, perhaps just above the sweet spot. Say 50-75 miles off the coast of the Cape. That would suggest a turn over to a mix on the south coast with jackpot amounts inland of Boston, south inland of Taunton, and further south on a line inland of Providence. Worcester and the hills could be crushed. Again my opinion.
2. The strength of bands of snow that "back over" the coast.
As the low pressure system travels northeast from the Cape, particularly when it is about 200 miles off the coast, east of Boston it will exemplify a traditional nor-easter and possibly a blizzard. This means that heavy bands of snow will back into the region from the north east and sweep across southern New England (and later up into Maine). The stronger the low pressure has become, the stronger the bands of snow will be. Look at them similar to the arms of a hurricane (because it's essentially a winter hurricane). This is where the vast majority of the snow accumulation will come from. These bands of snow could be cut down a bit if the rain/snow line from above is further inland. In which case, snow amounts will be limited significantly. I believe we will have less than optimal conditions for extremely heavy snow bands.
3. Strength of the arctic high pressure in Canada.
The strength of the arctic high determines how quickly the storm can move north and east. Slower means greater accumulation. Faster means lighter accumulation. The heaviest and most famous snow storms have strong high pressure in place, slowing the storm and extending the number of hours of snow.
Summary:
Current forecasts continue to claim that this will be an all snow event for southern New England. I disagree. I believe that the storm will track further west/northwest and will turn over to rain on the coast and Cape. I believe heavy snow will fall in the Boston suburbs and west out to Worcester, where they may see 20 inches of snow extending down through Hartford. Closer to a foot in Berkshire County and closer to a foot changing to a mix in Bristol County and eastward.
That said, if the low develops stronger than anticipated, add another foot to all totals.
= new reply since forum marked as read