As Metallica sings in the beginning of the song “All Nightmare Long”, luck does indeed run out. After getting lucky for nearly the entire winter without a major snowstorm, it appears that our luck has finally run out.
Today will be the literal calm before the storm with high pressure sliding off to the east, but still keep us dry despite plenty of cloudcover. After that, we turn our eyes to a developing low pressure system moving up the East Coast. This will likely be a potent storm when it gets up here, producing strong winds and quite a bit of precipitation. It’s also expected to stall out and perhaps make a bit of a loop, which means we’re looking at a long-duration storm, starting this evening, and likely not ending until Wednesday morning. That’s what we’re fairly certain about. What we’re not certain about is the actually track the storm takes, and where it stalls/makes a loop, and that is the most critical part of the forecast. Temperatures will be marginal to begin with, so a degree or two will make a huge difference. We’re not worried about any warm air aloft, so sleet and freezing rain aren’t a concern – just a good old-fashioned rain/snow line. With marginal temperatures, intensity will also help determine what falls, as lighter precipitation will be more rain than snow, while heavier precipitation will bring some colder air down from aloft, resulting in more snow than rain.
OK, having said all that, he’s our best estimate as to what we expect – low pressure moves up the East Coast, passing just south and east of Cape Cod. Meanwhile, a much weaker secondary low will move across Long Island and southern Connecticut, before it weakens and dissipates. This will help keep temperatures a little warmer, especially near the South Coast, with east to southeast winds. The original rather potent system will then do a loop in the waters just east of New England, before finally moving away on Wednesday. In terms of sensible weather we’re probably looking at nearly all snow north of the Mass Pike and outside of I-495, especially in the hills. South and east of there, precipitation likely starts as rain this evening, gradually changing to snow from northwest to southeast during the day on Tuesday as the system moves off to the east, and strong north to northwest winds bring cooler air in. Those winds will gust to 40-50 mph at times, but luckily tides are astronomically low, so coastal flooding isn’t a widespread concern.
As for snowfall, we need to make a distinction here between snowfall and snow accumulation. With the increasing sun angle, and the warmer ground, snow will have a hard time accumulating during the daylight hours, especially on paved surfaces, when precipitation is falling lightly. So, it could snow for quite some time, but there won’t be much on the ground. The model forecast maps that people love to share on Facebook and Twitter show snowfall, and as we’ve just said, those maps will not be reflective of what you may see on the ground when this storm winds down. What are we expecting for accumulation?
0-2″ – Outer Cape/Islands
2-4″ – South Coast/Upper Cape/Coastal Plymouth County
4-7″ – I-95 corridor (Providence/Boston), southeastern Massachusetts/North Shore
5-9″ – Metro West/Essex County/NH Seacoast
6-12″ – Merrimack Valley/Southern New Hampshire
8-16″ – Hilly terrain from northwest Rhode Island into central Massachusetts and southwest New Hampshire with isolated heavier amounts possible.
We will note that there are some models that do bring heavier (in some cases MUCH heavier) snow into eastern and especially southeastern Massachusetts. We’re not putting much stock in those. However, if they do end up correct, our snowfall forecast will be off by several orders of magnitude.
Once this storm pulls away, high pressure builds in with drier and more seasonable conditions for Wednesday night and Thursday. Another system may move in later Friday into Saturday, but this looks like mainly rain, with drier weather again behind that storm on Sunday.
Monday: Mostly cloudy, breezy, showers developing late in the day. High 40-47.
Monday night: Windy with rain likely, changing to snow across southern New Hampshire and central Massachusetts toward daybreak, rain may be heavy at times. Low 32-39.
Tuesday: Windy with rain changing to snow from northwest to southeast during the day. Snow and rain could be heavy at times. High 33-40 early, temperatures hold steady or drop during the day.
Tuesday night: Windy with snow gradually tapering off. Low 27-34.
Wednesday: Mostly cloudy and windy, snow showers ending. High 33-40.
Thursday: A mix of sun and clouds, breezy. High 42-49.
Friday: Becoming mostly cloudy, breezy, showers develop at night. High 45-52.
Saturday: Mostly cloudy, breezy, showers likely, possibly changing to snow before ending at night. High 45-52.
Sunday: Partly sunny, windy. High 37-44.