A scene from last week’s nor’easter.
Photo: AP

Coastal communities in Massachusetts are still cleaning up from last week’s potent nor’easter. They may want to put those efforts on hold, though. Another storm is set to impact the region by midweek.

The coastal flooding won’t be nearly as bad, but colder air means snow is expected to pile up across the Mid-Atlantic and Northeast. The active weather pattern is courtesy of a climate oscillation known as the North Atlantic Oscillation, which has been in record territory to start the month.

We all know last week was a nor’easter of epic proportion in terms of wind, waves and planes covered in vomit. The next storm to hit the region is currently creating blizzard conditions in the northern half of the Midwest and gusty, dry fire weather in the southern half.

It will skirt the Ohio River Valley on Tuesday before curling up the coast on Wednesday and Thursday. Because astronomical tides will be lower and the storm will move faster than last week’s behemoth, coastal flooding is unlikely to be as bad as it was in New England on Friday and Saturday. Areas that were hit hard, however, will be in a more vulnerable state and this could add insult to injury. Ditto for the winds, which won’t be hurricane force like they were last week, but could still cause damage to branches and power lines already weakened.

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One area where this storm will outperform last week’s nor’easter is snow. Coastal areas are still looking at a rain-snow mix, but some inland locations could get a foot or more of snow. Bands of snow that train north to south could create relentless snow and even offer a chance of thundersnow in parts of New Jersey and inland areas further north.

Somewhere, meteorologist and noted thundersnow enthusiast Jim Cantore is surely getting stoked.

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So while not historic, we’re still looking at high impact winter weather. The string of storms is coming courtesy of a climate pattern called the North Atlantic Oscillation (NAO). Right now, it’s in a negative phase, which usually translates to snowy U.S. and cold Europe. And this recent negative NAO is no exception with back-to-back nor’easters on tap in the U.S. and frigid air in Europe that allowed it to snow in Rome last week.

A negative NAO is also generally characterized by a big ridge of high pressure over Greenland, something meteorologists refer to as a Greenland Block. That in turn causes the jet stream—a river of fast flowing air that storms ride—to dip a bit over the eastern U.S., increasing the odds of wild weather in the region.

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“While the NAO is not the only factor at play, I believe it is definitely a driving force behind this pattern,” Ed Vallee, a meteorologist and owner of Vallee Weather Consulting LLC, told Earther. “Blocking high pressure in southeastern Canada has amplified the pattern as a whole and has allowed disturbances originating from the Pacific Ocean to glide across the U.S. while tapping into available moisture from the Gulf of Mexico.”

The current negative NAO bottomed in historic territory just as the last week’s nor’easter was tearing up the East Coast. It’s since slowly started marching toward a more neutral state, which is good news if you’re not fan of this recent spate of turn-umbrellas-inside-out weather.

“It appears the blocking pattern causing this increase in storminess will begin to break down toward the middle of the month,” Valle said. “In return, the pattern will likely shift back warmer and perhaps drier as we head into the back half of March.”