UPDATE, 4:15 p.m.: The winter storm watch for Boston has been upgraded to a blizzard watch. The National Weather Service now headlining “a potential historic winter storm and blizzard” with accumulations of one to two feet.

European model shows strong low pressure centered off the coast of New England (late Friday night into Saturday morning) dumping wind-driven snow inland. (StormVistaWxModels.com adapted by CWG)

A storm moving up the East Coast Friday will explosively strengthen, potentially dumping paralyzing quantities of snow in eastern New England. Questions still linger about exact amounts, but current model simulations suggest totals easily exceeding one feet are a strong possibility.

The National Weather Service’s Hydrometeorological Prediction Center officially sounded the alarm in its extended range discussion this morning with the headline: Chances greatly increasing for blizzard conditions over parts of the Northeast Day 3 [Friday]

Snowfall forecast for eastern New England from the NWS office serving Boston (National Weather Service)

The NWS office in Taunton, Mass. serving Boston piled on, writing:

Confidence is increasing in the potential for a very significant winter storm Friday into early Saturday.

The office has issued a winter storm watch for a large part of southern New England for the potential for over a foot of snow and snowfall rates of 2 to 3 inches per hour. In addition, it forecasts strengthening winds out of the northeast gusting to 50 mph by Friday night, reducing visibilities below one-quarter mile.

GFS model simulates a large area of eastern New England receiving at least one foot of snow through Saturday morning (WeatherBell.com)

The European model generally simulates about 15-25 (perhaps some locally higher amounts) inches between eastern Connecticut and Boston. The GFS model shows slightly lower, but still very impressive amounts from 12-20 inches or so.

Places like Hartford, Providence and Boston appear to be in the bullseye area for snowfall totals but slight shifts in the storm track could decrease amounts. If the storm shifts west, warmer air off the ocean might produce rain near the coast, cutting down totals. If the storm shifts east (farther out to sea), the intensity of snow would be lighter.

Farther south, into New York City, the forecast is more complicated. Precipitation is likely to start as snow Thursday night before changing to rain Friday. As the storm pulls off to the north and colder air trickles in, precipitation may turn back to snow.

“Moderate to possibly significant snowfall and strong winds are likely Friday night,” writes the NWS office in Upton, N.Y., serving New York City. It’s calling for 6 to 8 inches in the Big Apple, with significantly more to the north. These are numbers are subject to change and are highly dependent on the exact storm track.

Around Philadelphia, a brief period of snow is possible early Friday (with accumulations probably light) before a changeover to rain. Precipitation may end as snow showers briefly overnight Friday with little impact likely.

For Washingtonians hungry for snow, this is not the storm. Although a brief period of snow and/or sleet is possible early Friday, precipitation should change to rain and amounts should be light.