Weekly Outlook: March 12-18, 2018


Another week, another nor’easter. Once again, the hype train has left the station and is heading down the track at top speed. Without further delay, let’s get right to it.

Low pressure moving across the Tennessee Valley Sunday night will redevelop off the South Carolina coastline early Monday, then head up the East Coast. The storm will pass south and east of Cape Cod while rapidly intensifying. As is usually the case, this will bring strong winds and snow to the region. Obviously, the strength of the winds and the amount of snow will be dependent on how close the storm passes to New England, among other things. As you probably heard on Sunday, the vast majority of media outlets, as well as all of the Facebook Forecasters, and even the National Weather Service, are calling for very heavy snowfall from this storm. The reason for this is that many of the models are forecasting these amounts. Well, as a noted colleague has said in the past – “If the models were as good as everyone thinks, there would be no need for meteorologists”. Oh, we still think there will be some heavy snow, and we’re expecting plowable amounts, but let’s pump the brakes on the talk of “1-2 feet” or “12-18 inches”, or our personal favorite cop-out “10-14 inches+” (adding the plus so that if anything higher than that falls you can claim that your forecast was accurate).

GFS forecast for the progression of the storm on Tuesday. Loop provided by Tropical Tidbits.

Before the storm arrives, Monday will be a generally cloudy day, with temperatures right around where they should be in mid-March. Winds will start to pick up in the evening, and for most of the day on Tuesday, we’re looking at northeast winds of 20-30 mph, with gusts to 40-50 mph inland, and 60-70 mph at the coast. Yes, this may take down some additional trees, but coastal flooding will not be a problem this time, as tides are significantly lower than they were a week ago.

As for the snow, it should develop around midnight, give or take an hour or two, and quickly become steady and heavy. Heavy snow will continue into the morning, then lighten up a bit in the afternoon, winding down in the evening.  If you can work from home on Tuesday, we’d recommend it. Travel will be extremely difficult in the morning, as snow could be falling at the rate of an inch an hour or more, and it will be accompanied by strong winds, creating blizzard conditions at times.

Official definition of a blizzard. Note, snowfall accumulations do not factor into this. Image provided by WCVB-Boston.


As for how much, well, as we mentioned above, we’re not going with the big amounts that many others are. Why? Well, for one, a portion of that snow is going to fall during the daytime. At this time of year, the sun angle is strong enough (equivalent to the end of September), then unless it’s falling heavily, it will have trouble accumulating. Now, it will be falling heavily in the morning, but probably not as heavily in the afternoon. So, you can slice a little off of those model snow maps right there. Another reason is that we expect the models to shift a little more with the track slightly farther offshore. That has been the trend during the day today, and if that continues, it will result in lighter amounts. Yes, unlike the Facebook Forecasters who just take the what the models say exactly and call it a forecast, we use experience and education to figure out where the models are likely in error, and adjust accordingly. As for amounts, that likely means a general 8-12 inches across most of the region, with isolated heavier totals, especially across southeastern Massachusetts and the Cape. Across the Outer Cape and Nantucket, there is the possibility of some rain mixing in, which would keep accumulations lower.

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The snowfall forecast from the Sunday late-afternoon run of the GFS is closest to our thinking for the next storm. Image provided by Pivotal Weather.

Once the system pulls away, an upper-level low will move into the region on Wednesday, keeping plenty of clouds in place, with some additional snow showers possible. The upper-level low may linger into Thursday, with only a little more sunshine, and a slightly lower chance for snow showers. High pressure finally starts to build in for Friday and Saturday. By Sunday, the next system approaches the region. Right now, this system looks warmer, with rain, but given the way this month has gone, does anyone wanna bet that it stays that way? Anyone? Anyone? Bueller? Bueller?

Monday: Any early sunshine disappears behind increasing clouds. High 37-44.

Monday night: Becoming windy with snow developing, becoming heavy at times. Low 26-33.

Tuesday: Windy with snow, heavy at times in the morning, tapering off late in the day. High 29-36.

Tuesday night: Snow ending in the evening, remaining mostly cloudy with winds gradually diminishing. Low 24-31.

Wednesday: Partly to mostly cloudy and breezy with more snow showers developing. High 32-39.

Thursday: More clouds than sunshine, breezy, chance for a few snow showers. High 34-41.

Friday: A mix of sun and clouds, still breezy, slight chance for another snow shower. High 33-40.

Saturday: Partly to mostly sunny. High 37-44.

Sunday: Becoming cloudy with a chance of rain or snow showers. High 41-48.

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