First Alert Weather

First Alert Weather: Major Nor'easter Bearing Down on New England

Snow arrives in the Boston area by mid-afternoon Monday, if not sooner

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An expansive winter storm now impacting the area from Chicago to Washington, D.C., will engulf New England on Monday and last until Wednesday.

It is the same storm that dropped eight feet of snow on Mammoth Mountain in California Tuesday through Thursday.

Here in New England, we are in the coldest outbreak since probably January 2018, as the low temperature this morning was -25 degrees at Island Pond, Vermont. The low in Boston of 7 degrees is the third morning in a row in single digits. Ahead of this storm we have fading sunshine Sunday afternoon with a nice recovery back to the teens and 20s and some light wind.

TIMELINE: Track the 3-Day Winter Storm Approaching New England

With all this cold, we are going to see a strong storm centered close enough to Nantucket with wind coming in off the ocean, and with a water temperature of 41 degrees, there will be enough warmer air for a challenging snow/rain line.

There will be a ring around the moon Sunday night; the old saying "ring around the sun or moon, snow or rain soon" certainly will come true. Low temperatures overnight are again well below zero in northern New England to the teens in the 20s toward the South Coast.

Snow develops on the South Coast shortly after sunrise and slowly pushes to the north. It will not take long for snow to be accumulating at 1 to 3 inches per hour, even where a change to rain is expected, we may have to plow snow before the change. So in the first three or four hours of the storm, there will likely be more than 4 inches of snow -- that’s about how long it may snow before changing to rain from the coast of Connecticut to Cape Cod.

Snow arrives in the Boston area by mid-afternoon Monday, if not sooner. Near the mix line -- snow will not be as deep as inland -- this will be the most challenging and hardest hit area, due to heavy wet snow and powerful wind causing power outages tomorrow night.

It looks like the most powerful band of snow should last about 8 to 10 hours in any one location. In a normal storm we might say 8 to 10 inches in that amount of time, but there is such a strong gradient between the very cold high pressure system to the north and the relatively warm low pressure system to the south that snowfall of 8 to 10 hours may add up to more like 10 to 15 inches.

The band of snow will push out of southern New England early Tuesday and into northern New England and keep on going. There are actually two low pressure systems, maybe even three that are going to develop, and then redevelop and slowly move from Nantucket into the Gulf of Maine. So we will be constantly tweaking the forecast throughout the long duration event.

The worst of the wind is likely toward the high tide Monday night -- that’s when we will be gusting past 50 mph from the northeast. Coastal erosion and minor to moderate coastal flooding is likely. The high tide early Tuesday afternoon may not be as dramatic, but could come with some more issues. Precipitation should ease to light snow, perhaps some freezing drizzle or drizzle on Tuesday in southern New England as snow continues toward the Canadian border.

Wind will pick up from the north Tuesday night and any liquid precipitation will change back to snow, with deep puddles toward southeastern New England refreezing by Wednesday morning. Clouds and occasional light snow will likely persist through midday Wednesday.

Snowfall accumulation is likely 10 to 20 inches where it stays all snow, with some of the higher elevations coming in closer to 2 feet. There will also be some holes in the snow accumulation on the windward side of some of the mountains. In eastern Maine, snow likely changes to rain and then back to snow and ice, so that will keep accumulations down but it will still have a high impact.

We get a little rest on Thursday before a warm front brings a mix of rain and snow showers early Friday, then it’s windy and warmer with a chance of rain Friday into Saturday before turning dramatically colder again late next weekend and into the following week. It is a very busy First Alert 10-day forecast.

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