The quickly intensifying storm may even become a meteorological “bomb” as its impressive rate of strengthening is sufficient to spell big impacts. Snowfall rates of 1 to 3 inches per hour are likely near and west of Interstate 95 in Massachusetts, New Hampshire and Maine, along with whiteout conditions and possible thundersnow.
The heavy wet snow may weigh down tree limbs and utility lines, leading to power outages in some areas.
Near the coast, a period of strong winds could also bring scattered power outages.
It’s a tricky forecast for some cities like Boston, Portsmouth, N.H., and Providence, where the all-important rain-snow line could prove the crucial wild card between a plowable, sloppy snow and a drenching rain. Current forecasts indicate the height of the storm will occur Saturday, but northern Maine can expect lingering snow into Sunday.
On Friday, two distinct weather systems were in the process of coming together, or “phasing,” to produce a more powerful nor’easter. A surface low exiting the Tennessee Valley will move offshore of the Mid-Atlantic, where it will be energized by an upper-level disturbance swinging south out of Ontario. That will invigorate the surface low, inciting a period of “bombogenesis,” or the rapid development and deepening of a low pressure system, overnight Friday into Saturday.
The nor’easter would officially be considered a “bomb cyclone” if its pressure drops 24 millibars in 24 hours, which is predicted by some models.
The storm’s rapid strengthening will intensify its winds, especially near the coast, while also contributing to heavy precipitation. The system will probably pass close to the coast, its axis of heaviest moisture in the perfect zone to bring significant rain and snow.
Counterclockwise winds feeding into the system will pull chilly air in from the northwest, allowing the rain-snow line to collapse toward the coast. That could give places like Boston a brief shot of snow on the backside of the system. Over southeastern Massachusetts and Down East Maine, both places likely to get into the warm sector of the storm, rain primarily is expected.
Timing and impacts
Light rain will fall intermittently across southern New England on Friday afternoon, but at first it may not reach the ground. This rain will help with evaporative cooling, however, chilling the low levels of the atmosphere and laying the groundwork for later snow. By Saturday morning, heavy rain will be ongoing over most of Massachusetts, Connecticut, and Rhode Island, the first flakes beginning to fly in the Berkshires and the Worcester Hills. Over time, that snow line will creep south and east.
Around lunchtime, snow will be falling in the hills of northwest Connecticut, and will have made it to near Interstate 84. Worcester could see flakes by noon. Meanwhile, inland snow will have broken out across northern New England, including most of New Hampshire and Vermont, with borderline conditions near the coast making either rain or snow a possibility.
As sunset nears, most of New England with the exception of Vermont will be seeing moderate to heavy precipitation. Snow will probably be falling in Hartford and flirting with Providence, while also coming down steadily over most of central and western Massachusetts west of the Blackstone Valley, N.H., and Maine away from the coast. Snowfall rates of 1 to 2 inches per hour are possible.
The system will pull north, a band of heavy snow surging toward metro Boston on Saturday night with brief heavy snow and an isolated clap of thunder. Whiteout conditions are possible for a time. Meanwhile, the worst of the winds will be ongoing — 30 to 40 mph inland, 40 to 50 mph for Cape Ann and along the New Hampshire and Maine coasts, and 50 to 60 mph for Cape Cod and the Islands.
Snow lingers in northern New England on Sunday, along with a few ocean-effect snow showers on outer Cape Cod, mainly between Orleans and Truro.
Across northwestern Connecticut and much of Massachusetts near and north of the Massachusetts Turnpike, a broad 1 to 3 inches is possible. Four to six inches is likely in the northern Berkshires and also the Route 2 corridor of north-central Massachusetts.
Boston may see an inch or two, but in a brief window on the storm’s backside.
Six to eight inches will probably fall over much of New Hampshire, with the greatest amounts north and east. Elevation will play a role too, with cooler temperatures that can fluff up snow.
In Maine, the heaviest snow will fall away from the coast, with 1 to 3 inches along the shoreline quickly building inland. Totals of a foot or more are possible in northern and western Maine. Down East Maine will see little to no snow due to the track of low pressure, which will tug warm air ashore.
Instead, extreme eastern Maine, Cape Cod, and southeast New England will pick up a good shot of rainfall, with two inches or more when all is said and done.
If enough cold air is present, some of these amounts, especially inland, could be easily doubled, lending to a highly difficult and uncertain forecast.
Heavy rain in the Mid-Atlantic
Some of that heavy rainfall may also come down in the Mid-Atlantic during the onset of the storm, primarily late Friday night into Saturday. It now appears that, with a slightly more northeastward track of the storm, the heaviest rain should fall just east of D.C., Baltimore, New York and Philadelphia. Still, the cities could wind up with an inch or more of rain.