This storm will pack a punch, but it’ll be gone quickly

Power outages are virtually guaranteed across southern New England.

–Dave Epstein for The Boston Globe

After a beautiful day on Saturday, things are rapidly going to go downhill Sunday afternoon and into the overnight. In thinking about this storm, my brain flashes back to the 1991 “Perfect Storm.’’ In that situation, highly unusual elements came together to create a monster storm.

This isn’t the same situation, nor will the storm be as significant. However, we do have a very strong cold front coming in from the west and we do have an unorganized tropical system named Phillipe, which will add to the entire event.

This storm also will produce very heavy snow near Hudson Bay in Canada.

3 parts to the storm

The two known components of this storm are heavy rain and wind. There’s a third possible component, though: strong to severe thunderstorms.

This is an unusual meteorological setup. For those of you who like math, the trough, which is the dip in the jet stream, is about five standard deviations away from normal, meaning it’s highly anomalous. Additionally the amount of moisture that’s going to be present in the air during this event is also about the same place on a normal curve. You can see this dip on the water vapor loop below.

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Intense, but not long lasting

Everything’s moving quickly, so the risk of rain and thunderstorms ends early Monday. Nonetheless, winds are going to be a factor throughout the day Monday.

Power outages are virtually guaranteed across southern New England. The greatest risk of outages will be on Cape Cod and the islands, but most parts of Massachusetts are under a high wind warning, so watch out for downed trees and power lines. There also is a flood watch active, which is is mostly for urban and small stream flooding — not river flooding.

We could see some showers late Sunday morning and early Sunday afternoon, but the heaviest rain won’t arrive until after dark. There’s likely to be two bullseye of maximum rainfall: one over the Berkshires and portions of New York state, and the other somewhere between Route 495 and Cape Cod — that one depends on how much moisture from Philippe moves northward along the cold front.

—National Weather Service
—National Weather Service

Questions remain

The strength of the wind could still end up being less than forecast. Winds are going to be very intense a couple of thousand feet above the ground; what we don’t know is how much of that mixes down to the ground.

—Dave Epstein for The Boston Globe

Delays and cancellations

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There could be flight delays at Logan Airport, and I wouldn’t be surprised if some areas see school cancellations or delays Monday morning if the winds are really powerful early.

On the horizon: better weather

The heaviest winds depart by 8 a.m. Monday, but gusty winds remain all day. Halloween looks dry and seasonable.

Weather
It's snowing in parts of Maine
November 13, 2017 | 12:53 PM