A strong nor’easter will affect Southern New England overnight and into Tuesday evening. This storm will bring a variety of weather including torrential rain, heavy snow, strong winds, and coastal flooding.
Although the storm will start as rain, it will transition to snow early Tuesday morning across northern, far western, and the higher elevations of southern New England. During the latter half of the morning and into the afternoon on Tuesday, the rain will turn to snow right at the coastline. While this is happening, winds will be increasing.
There will be banding of the snow on Tuesday from late morning through the afternoon. Some of these bands could be incredibly intense to the point that travel becomes almost impossible where those bands occur.
Even if temperatures are above freezing and you have snowfall rates of 1 to 3 inches per hour, the cold snow will cool the ground and the roadways fast enough that accumulation will take place. The heaviest snow will likely take place between roughly noon and 7 p.m. It’ll be hours earlier west and north of Route 495. Parts of western Massachusetts could see snowfall rates of 2 to 3 inches per hour pre-dawn Tuesday morning.
Locally, there still can be bands of snow rotating through Greater Boston on and off until after midnight, but not with the same intensity. I would not be on the roads in areas where these bands occur Tuesday. I would not be surprised if we even had reports of thundersnow in these bands.
The risk of power outages will come from both the heavy snow and the strong winds. Some areas will have both of these elements. On Cape Cod, it will just be the wind.
If you receive more than 4 inches of heavy wet snow, your area will likely experience power problems.
When the storm is eventually over, and we look at the total accumulation of snow, I suspect we’re going to see a tight gradient from those areas with a coating to a couple of inches all the way up to half a foot and beyond. The highest amounts will be across higher elevations and farther north.
My snowfall map has this very tight transition between just a few inches and over half a foot that could easily wobble a little west or east. If a band of heavy snow rotates through your area, there can be locally higher amounts, even in the areas with less snow predicted.
In terms of precipitation, either all rain or melted snow, the water equivalent will be two to three inches. This is enough to cause urban street flooding and some basement flooding. I don’t suspect we will see rivers or streams having any issues.
Winds will pick up Monday night and continue to be gusty and strong along the coastline right through Tuesday evening before diminishing by Wednesday. The storm will undergo rapid intensification, and the increasing pressure gradient will produce the wind.
Coastal flooding will be minor to moderate, but because the tides are not astronomically high, we shouldn’t see major coastal flooding. This is a fortunate aspect of the timing of the storm itself.
In summary: Rain arrives overnight. Then rain changes to snow (west to east) Tuesday and tapers to lighter bands of snow overnight before ending Wednesday morning. The most intense part of the storm for Greater Boston is Tuesday afternoon and early evening. It turns mild and drier for the end of the week with plenty of melting.