Our winter storm is panning out mostly in accordance with the forecast with one important exception. The coastal front is a few miles farther SE than forecast which means areas like Portland, Falmouth, Brunswick, Augusta, Waterville, and other towns in that area will get a bit more snow than forecast.
The coastal front is also the rain/snow line with warm maritime air, rain, and temps in the 40’s on the SE side and cold air, snow, and temps in the 20’s to low 30’s on the NW side. The coastal front is a few dozen miles SE of its forecast position and the track of the low itself appears to be a bit SE of forecast as well. This means that there is a limited window of opportunity for the coastal front, and thus the rain snow line, to move NW.
The wider surface picture shows our storm developing rapidly just offshore with 3 hour pressure falls in excess of 6mb. as the storm explodes just to our east, it will begin to wrap cold air in from the west and the rain/snow line will crash to the coast. As I mentioned in last night’s update and the one on Tuesday night, the precipitation will be coming down very heavily. Radar imagery shows that this heavy precip is developing as the intense upper dynamics begin developing.
As the warm air offshore collides with the cold air across the interior, not only will the low develop rapidly, but the heavy precip bands will too. The mid level forcing map shows these bands beginning to develop across coastal Maine and southern New England. These bands will continue to intensify this evening as they move slowly NW and in some of the stronger bands, thunder is possible. Snowfall rates of 1-3″/hour are expected in these bands along with whiteout conditions. The heavy precip will dynamically cool the atmosphere so the rain/snow line will be crashing to the coast tonight.
For all the detailed analysis, check out the updates I linked to above. The snowfall map still looks good except for the coast where higher amounts are possible due to the lack of NW progress of the coastal front.
Strong winds are also still expected with power outages a threat especially for those areas with lots of snow to weigh down trees and power lines. Winds will wind down tomorrow afternoon and evening.
I’ll be tweeting this evening with more updates, you can follow me there @JackSillin