We have some exciting weather coming this evening and into tonight as a storm offshore develops explosively. For full details and analysis, check my updates from last night and Tuesday night which detail many of the important dynamics behind the storm. This update will be a quicker/more concise forecast focused mostly on impacts and less on meteorology.
Snow has begun in association with low level convergence along the coastal front. This snow is currently in coastal York and Cumberland counties and will drift north through the morning hours. This snow is light and accumulations, if any, should be under an inch.
The main event will begin across the area from SW to NE midday today. Snow will begin with moderate intensity around 10 AM in SW NH and around 1PM in far NE areas. While everyone will likely see some flakes initially, the change to rain will be swift along the midcoast and in York county while interior Casco Bay might see an inch or two before turning rainy. By 3 or 4 PM, our pattern will be locked in with moderate snow inland and moderate rain east of the turnpike.
Heavy bands of snow will begin to charge inland after sundown this evening and by 7 or 8 PM, heavy precip will be impacting most of the area. In the mountains, this will mean whiteout conditions as snow falls at 1-3 possibly 4″ inches/hour. Combined with strong winds, expect blizzard conditions even though it may not officially be termed a blizzard. Along the coast, this will mean heavy rain along with gusty winds.
Later in the evening, dry air will wrap into the system aloft. While this may decrease the areal extent of the heavy precip by some, it will also trigger instability which means thunderstorms will likely develop and move north during the overnight hours. Thundersnow (!!) is a strong possibility in the foothills and mountains.
Wind will be the other big threat. High wind warnings are up for the midcoast where gusts over 60mph are expected. These winds will be on the front side of the low and along the coast SW of Brunswick, these winds will gust in the 50mph range. After the storm makes landfall between Brunswick and Boothbay Harbor, winds will whip around to the west where they will resume gusting over 50mph this time for the entire area. The combination of very strong winds and heavy snow will create blizzard conditions inland for a time later tonight. The strong winds will also likely create power outage concerns especially in areas with 1-2 feet of snow already weighing down trees and power lines.
Snow moves out early Friday morning with upslope bands continuing to keep the powder fresh on the slopes. Additional upslope amounts of 3-6″ are possible in the favored areas given strong WNW flow and abundant low level moisture.
More (lighter) snow is in the forecast for NYE.