Midday Christmas Update from Meteorologist Matt Noyes
Summary: We remain on-track for a major snowstorm for most of Southern, Central and Eastern New England Sunday afternoon through Monday. Good agreement on 12-18" of snow for most eastern areas. Blizzard conditions possible from Plymouth County MA northward to the Maine coast overnight Sunday night.
Confidence: Upgraded to High confidence of a 10"+ event. Moderate confidence of blizzard verification from Plymouth County to Essex County MA, low confidence farther north along the coast. Blizzard watch may be issued later Christmas Day for the Sunday night time period.
Variables: A large shift in storm track that would negate a heavy snowfall is now very unlikely. Even the farthest east outlying track indicated by a small minority of guidance would still deliver 10"+. A slight eastward shift would, however, reduce the chance of reaching blizzard criteria (frequent 35 mph gusts, visibility 1/4 mile or less, duration of 3 hours continuous).
Timing: Accelerated by three to four hours. Still expecting first flakes late morning/midday, but steadier and heavier snow spreads from South Coast at noon/1 PM to MA/NH border between 4 and 7 PM. Heaviest occurs overnight Sunday night and still coming down heavily in the Boston area Monday morning, tapering in intensity by midday but not shutting down entirely until late in the day.
Intensity: Current indications are that the heaviest snow would fall 7 PM Sunday to 7 AM Monday. Hourly snowfall rates in the middle of the night Sunday night may reach 2"/hour, but will diminish to .50-1.0"/hour by the start of the morning commute, though roads would be a mess by that point.
Accumulation: Most of New England will receive accumulating snow, with lesser amounts in Northern Vermont and Eastern MA/Southeast NH hit hardest with snowfall totals generally 12"-18". Metropolitan areas from Baltimore/Washington (Sunday midday) to Philadelphia (Sunday evening) to NYC (overnight Sunday night) to all Metro areas of Southern New England, Southern NH and Southern ME (all Sunday overnight thru Monday AM) should see significant impact.
Other concerns: Scattered wind damage is possible along the Massachusetts coastal plain overnight Sunday night. Minor coastal flooding is possible at the time of high tide (just past 3 AM Sunday night, 3 PM Monday afternoon) on northeast facing shorelines. Minor coastal flooding can sometimes include flooding of prone homes and businesses. This potential will become clearer as we near the storm.