Winter is making a big offensive push against the torch this week and Maine is right on the front lines. We have three storm threats this week, tomorrow, Tuesday, and Thursday/Friday. This post will focus mostly on tomorrow. I’ll have full updates on Tuesday’s storm threat starting tomorrow evening. Due to how far out the New Year’s storm threat is, I’ll save that for after we clear the first two.
Rain and snow will move into the region late tonight into tomorrow morning. Look for initial mix for most areas turning to rain first at the coast and then inland. Everyone is at risk for slick spots in the morning even the coast. Major issues aren’t expected but just use extra caution and remember, roads start to get slick around 35 degrees so even if your car thermometer says 34, that doesn’t mean that roads can’t slick up.
The rain/snow line will creep northward tomorrow and cold air will become entrenched just east of the mountains. As a result, this becomes a 3 part storm. Coastal/Southern rain, foothills/inland mix, and mountain/northern snow. Look below for a complete impact map. My biggest concern here is the weak winds aloft. I think the models are too quick to warm the mid levels of the atmosphere given a lack of strong winds to blast warm air in. If there are surprises with this storm one of them very well could be areas near/just south of Route 2 stay snowier for longer.
Another thing to be worried about here is Cold Air Damming and associated icing threats right up near the mountains. Winds will be southeasterly and will thus warm air at the surface will flood most areas. Temps will cool this evening setting up a pool of cold air. This will easily be pushed NW for the most part by SE winds. The cold pool of air will run into issues near the mountains though as it can’t really go anywhere. Cold dense air doesn’t like to climb mountains and I think that while eventually the SE winds will gather the energy to get the cold air out of there but I think it could take a while. Don’t be surprised if there is a little more freezing rain/sleet/snow than forecast.
Behind tomorrow’s storm comes a large area of Canadian high pressure. This will ensure a steady supply of cold dry air to do battle with a steady flow of Gulf of Mexico moisture. This battle is what will produce our snow. With such massive, powerful, and cold high pressure close to our north, I have a hard time believing there will be any widespread intrusion of warm air for Northern New England. Rain could make an appearance at the immediate coast but it’s about 5,000 feet above our heads that warm air could present the most problems.
Here is the 18Z NAM temps 5,000 feet up Tuesday Evening. By this time most of the heavy snow will be out of the way but This map shows how warm air will be rapidly approaching the region as precip is rapidly leaving. It is too early to tell exactly who will change to sleet and for how long but just be aware of the potential especially for SW areas. If totals come in a little lower than expected, this might be why.
This event looks like a heavy burst of snow followed by a lighter, drizzlier precip. The exact timing is still to be determined but sometime during the day looks like the most likely time for a 6 hour or so burst of heavy snow before the mid levels dry out enough to shut off the steady precip. After the first burst of snow, look for lighter snow/sleet/freezing drizzle. This remaining light precip should taper off Tuesday night before fully clearing out Wednesday morning.
A coastal low will also develop and move east Tuesday evening bringing with it the tropical moisture connection. Its development will also help keep cold air locked in inland and will intensify a coastal front that is likely to develop along the immediate coast. The GFS also shows the light and showery nature of precip Tuesday Evening.
In terms of amounts, too early to tell is the name of the game for now. The most I could see out of this event is 6-10″ probably across the foothills into the western mountains. The coastal low will likely keep the moisture SE enough so that Jackman north won’t see as much liquid. The coast is at the mercy of the coastal front and warmer temps while SW areas could see sleet mixing. I’ll have more details tomorrow evening on amounts but a general 4-8″ seems likely with some 10″ amounts definitely possible.
We get a quick break Wednesday but never really clear out fully before our next storm arrives Thursday. That one looks like mainly rain with a mix up north as of now.