There’s reasonable model agreement that low pressure will develop off the Southeast or mid-Atlantic coast late Tuesday and move north, producing a range of effects from the mid-Atlantic to Northeast Wednesday and Thursday.
Exactly where the low develops and where it tracks will determine the effects for particular areas. But it looks increasingly likely that from the Delmarva to New England, the coastline is in for another battering, though with lesser severity compared to Sandy.
All four of the primary global models, the GFS, the Canadian, the UKMet, and the European (EURO) show a storm forming, but in different locations. The GFS and the Canadian develop the storm too far off the coast and too late for significant precipitation in the D.C. metro region. On the other hand the European and UKMet would suggest a period of rain for the D.C. area Wednesday, possibly changing to snow into Wednesday night, especially in the north and west suburbs and mountains. We may even be looking at some accumulation if the European model, in particular, is right.
“This is a case where two different upper level impulses have to phase correctly to get the Nor’easter to develop far enough west to give Washington, D.C. storm conditions,” said CWG winter weather expert Wes Junker. “In such cases the timing of the two waves has to be almost perfect to get a storm.”
“In summary,” Junker said, “the models are split into two camps one offering a more wrapped up solution with the low closer to the coast (European and UKMET models) and a flatter solution with any strong development of the low far enough east to keep D.C. dry.”
Unfortunately, all four models indicate a period of onshore flow for both the mid-Atlantic and the Northeast capable of producing coastal flooding and beach erosion, and potentially strong, gusty winds (but not at Sandy's intensity).
This is exactly what coastal areas, reeling from Superstorm Sandy, don’t need.
We’ll have a more detailed outlook on storm scenarios Sunday. And the snow potential index for the D.C. area is likely to come out of the closet!