Nor'easter brings concern for coastal flooding

A coastal flood watch is in effect from Friday morning through Saturday afternoon for the entire eastern Massachusetts coastline from Nantucket to the New Hampshire border.

As we turn the calendar page and kick off meteorological Spring (March, April, May), a nor'easter is expected to land off the coast of southern New England. There is still a layer of uncertainty with this system but as of Tuesday morning, here is our thinking:

The timeline has overall remained steady since Sunday's guidance models. The low pressure will be developing and eventually land itself south and east or Cape Cod on Thursday evening. Rain will be the initial type of precipitation and that remains the case during the day on Friday. By Friday evening, a transition to some pasty, wet snow is possible as temperatures fall. The showers are expected to come to an end Saturday morning.

When we focus on a system this far in advance, there is generally some discrepancy with the ultimate location of it. I'm finding that's not the case this time. The GFS (American model) and ECMWF (European model) are in good agreement in where the low (indicated by "L" in the image) will land. When an area of low pressure nears 40°N and 70°W (blue lines and "X"), southern New England usually tops the list of accumulation/precipitation totals. That's seems to be the case this time as well, but, it's looking like mainly rain rather than snow.

At this time, rain totals seem to land between 1.25-1.75". Some locations could reach 2" before transitioning to snow. The GFS model is suggesting an inch of snow for parts of our region, but it will be wet, heavy snow and shouldn't look too impressive.

The precipitation isn't really the concern with this storm. The winds are going to pick up quickly and could be damaging at a point. Gusts could exceed 50mph with even stronger winds near the coastline. That wind with the combination of astronomical high tides will make the waters very rough. Latest indications suggest that offshore swells could reach 20+ft. This is a big issue for boaters and commercial fishermen. For surfers, this may sound enticing, but heir on the side of caution with this system. Friday will be a tough day. Those swells will not be crashing into the coast, but water will pile up for those living near the water. Steps should be taken to limit possible flooding damage.

Information can change over the next 24-48 hours so keep checking back in with the StormTeam10 crew both on this blog as well as on-air.

-Meteorologist Zack Green

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