A major Nor’easter is on its way, with snowfall expected from late Sunday night through all of Monday.
Low pressure developing off the Mid-Atlantic coast will rapidly intensify over the next 24 hours, developing into what’s known as a meteorological bomb, with very low pressure south of Nantucket on Monday morning.
Meteorologists use the term “bombogenesis” when storms intensify at least one millibar every hour for 24 hours. A millibar is a unit of pressure — think of it like a unit of measure for the air on top of us. At that rate of intensification, they’re often accompanied by very strong wind and heavy precipitation. Massachusetts is set to get both.
Snow will arrive most likely after midnight in Boston, with earlier arrivals to the south and west of the city. When you get up Monday morning, there may already be between five and 10 inches of snow on the ground, with as much as another foot during the morning and first part of the afternoon.
In general, most areas of Massachusetts east of Interstate 495 will experience one to two feet of snow, with the highest amounts likely across Rhode Island and into the southeast interior Massachusetts. Boston itself will be close to those heavier totals.
With storms this large, a phenomenon called “banding” comes into play. Banding happens when air rapidly rises, leading to very heavy rates of precipitation. In this case the snow will be falling at one to three inches per hour just before and after sunrise on Monday. Combined with the wind, visibility will be under a quarter mile. Along the coastline, winds could top 35 mph, creating blizzard conditions.
The snow will become less intense Monday afternoon and likely die off completely between 5 p.m. and 9 p.m. from west to east.
The snow will start a little bit heavier and wetter, but trend drier as cold air works into the storm. It will not become excessively cold, though with the wind it’s not going to be comfortable.
Nor’easters can bring significant coastal flooding, but Massachusetts should see just a bit of moderate flooding at the time of high tide early Monday morning and again Monday afternoon. The wind will be veering to the north in the afternoon, which will help keep the water from piling up too much. Even so, residents can expect some shore road closures and beach erosion.
School closures should be expected for Monday and potentially into Tuesday as municipalities deal with cleanup. Logan Airport could see a significant impact on Monday, and travel delays should be expected in general. Roads will likely be cleared for travel by Tuesday morning.
Temperatures will be just above freezing on Tuesday afternoon with lots of sunshine before rain or lesser amounts of snow arrive on Wednesday.
