Major snow storm Thu-Sun

Confidence is growing for a long duration major snow storm for portions of New England from Thursday through Sunday.

The storm that came through yesterday that dumped a few inches of snow is associated with an elongation of the polar vortex. This huge trough will rotate into the North Atlantic, setting up a strong -NAO block.

Back west, we have a number of shortwaves to discuss that will come into play.

1) Lead shortwave in the southern stream
2) Primary shortwave in the southern stream
3) Shortwave in the northern stream


The lead shortwave comes into play first with respect to sensible weather in New England. Vorticity advection along with warm advection ahead of the northern stream shortwave will generate light precipitation across the region on Thursday. Precipitation should begin as snow, possibly mixing with sleet and rain up into northern Massachusetts as warm advection raises mid level temperatures. Any accumulation will be under 3".

The next stage begins late Thursday night with the primary southern stream shortwave. The wave will move toward the Delmarva peninsula on Friday, triggering weak cyclogenesis south of New England. Precipitation will spread north ahead of the low. Temperatures will be marginal for snow away from the coast. Coastal areas will likely see rain initially. This senario is certainly changeable. A sharper shortwave would trigger stronger cyclogenesis. This is also a function of the strength of the lead shortwave.

Friday night, the southern wave will lift northward up the coast, and the northern wave will begin to come into play. By Saturday morning, the two wave will be phasing, and developing into a closed upper low over New England. This upper low captures the surface system, and is held in place by the strong -NAO block. Model guidance has been suggesting the storm continues to affect New England potential as late as Monday. Where the low stalls will determine what areas will be under its constant influence.

At this point, the primary target area is Maine, where the stalled low may be dumping moderate to heavy snow for 2 days straight. Again, this could change. As long as the capture and stall senario remains constant however, some portion of New England could see accumulations of 2 to 4 FEET before all is said and done.

A very preliminary guess for snowfall Thu-Sun: