Storm cranking up off Mid-Atlantic coast and poised to move southeast of Nantucket by about 150 miles. This storm is loaded with southern stream moisture and will crank that moisture northward, and with an expanding counter-clockwise flow, Atlantic moisture will be pulled into the mix and will enhance accumulating snow potential. This has already been evidenced by bands of moderate snow that will continue to pile up across Eastern Massachusetts and Eastern New Hampshire, reaching amounts of 2" to 4" by early afternoon with localized amounts of 6" in heaviest banding (Newmarket, NH, already had 4" as of this mid-morning update), when the intensity of the snow should start to diminish for these areas. This surge of snow is caused by an influx of Atlantic moisture on an increasing northeast wind at the surface, and easterly wind aloft, in advance of the expanding and quickly strengthening storm. While the snow will lose intensity for many areas Sunday afternoon, the opposite can be said on the Cape and Islands, and Southeastern Massachusetts, where the northwest periphery of the heavy precipitation shield associated with the ocean storm will start really dumping snow Sunday evening and throughout Sunday night. Snow is likely to fall at between one and three inches per hour on Cape Cod overnight, with snowfall rates largely dependent upon just how wet and compacted the snow is. In any storm on Cape Cod where deep arctic air isn't in place, we usually can bank on a sloppy, wet snow that doesn't pile up as quickly as the snow farther inland, largely because even a cold north wind will blow over warmer ocean waters, and can only be offset when deep arctic air is in place. This isn't an example of deep arctic air mitigating the effects of the ocean, so while the northeast and then north wind will be enough to keep the precipitation as snow, it will have a somewhat wet consistency, limiting how quickly it will pile up. Nonetheless, such snow is slippery and greasy on road surfaces, and driving will be extremely hazardous on Cape Cod with the combination of heavy snow, low visibility, and strong wind. The winds pick up throughout Sunday but really crank as the large storm center makes its closest pass overnight Sunday night, kicking up to a steady 15-30 mph for most coastal areas, but sustained at least 30-40 mph for a time on Cape Cod, with northeast and then northerly gusts at up to 60 mph. This wind will add extreme stress to trees and powerlines, weighed down by the heavy snow and likely to tumble under the increased stress of the wind, causing power outages Sunday night and Monday for most of Cape Cod. Winds will continue gusting with new damage Monday morning, then die down later Monday. As for total snow accumulations in Southeastern New England, I'm expecting about a foot of snow on the Outer Cape. Enough precipitation will fall that amounts near a foot and a half would be possible if not for the wet nature of the snow, but heavier banding may bring amounts greater than a foot for some communities of the Outer Cape and Nantucket. The farther north and west one is, the less snow that's expected to fall, but we have to consider the first burst of morning snow on Sunday will couple with additional snow Sunday night, which will probably bring storm total accumulations either side of 8" in Western parts of Cape Cod, and 6" to 8" from Plymouth to New Bedford. With a rather sharp northwest edge to the heavy precipitation, only an additional inch may accumulate around Boston to Norwood to Providence, with lesser additional amounts farther northwest.
You can follow the snow with the radar links on the right throughout Sunday and Monday. Current warnings and advisories, as well as current surface observations and satellite imagery, are linked at left. The forecast has been updated on my New England Forecast Page, ski area information has been updated on my Winter Sports and Recreation Page, your pictures from across New England are continuously being updated on my New England Photos Page, and Joe Joyce continues his storm coverage on NECN and NECN.com.
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