Snow showers today, clipper brings burst of snow from eastern Ontario to southern Maine tonight; yo-yo through Wednesday, then springlike weather dominates late next week into early following week; perhaps cooler but not particularly cold afterward

Plain-language summary:

Widespread snow showers are bringing light accumulation to most areas along and northwest of the Appalachians today, and then a burst of moderate to heavy snow will affect a narrow zone from eastern Ontario to southern Maine tonight. It will then turn much warmer on Tuesday and then much colder on Wednesday, but staying mainly dry. It will still be mainly dry while turning much warmer and more springlike through Saturday, though a little rain and/or snow is possible on Thursday. Thunderstorms are possible later Sunday into Sunday night before turning colder but not particularly cold early the following week, with another potential storm and/or warmup possible shortly afterward. There is some indication that cooler weather could come back in late March, bringing the chance for late-season snow, though that is still uncertain, and it will be getting increasingly difficult to get substantial snow accumulations in lower elevations.

Meteorological discussion:

Widespread snow showers today, burst of snow from eastern Ontario to southern Maine tonight

A very weak disturbance over southern Quebec is providing snow showers over our region, especially along and northwest of the Appalachians. Some higher-resolution models, such as the HRRR and NAM 3-km showed widespread convective snow showers and squalls, but the thick cloud cover is limiting the low-level instability and lapse rates, except in eastern Ontario where there is more sunshine and instability sparking more convective snow showers. Those will mostly dissipate tonight, but a clipper will quickly dive in from the northwest tonight. Although the clipper is not very strong, it is working with a pronounced temperature contrast between arctic air to the north and springlike weather to the south, with the warmth enhanced by the stronger March sun angle. This contrast will lead to rather strong dynamics and a zone from eastern Ontario to southern Maine that will see a few hours of moderate to even heavy snow, accumulating up to 3" (8 cm) in some spots. This will likely mark the last snow for most for at least 10 days or so.

Source: TropicalTidbits

Yo-yo temperature pattern through Wednesday

After the clipper, a stronger low-pressure system will quickly move into northern Ontario and then northern Quebec on Tuesday, bringing in a brief surge of warm, springlike air from the southwest, followed quickly by an arctic cold front Tuesday night. With the air mostly coming from the Plains and Rockies and not from the Gulf of Mexico or western Atlantic, it will be mostly dry with just a few showers along and northwest of the Appalachians with the arctic cold front. Wednesday will be much colder even if sunny with the arctic high pressure overhead, with most areas along and northwest of the Appalachians staying below freezing all day. 

Source: TropicalTidbits

A little rain and/or snow possible Wednesday night into Thursday, then springlike weather dominates later in the week

However, the cold air will be short-lived. As mentioned in the blog a week ago, the ridging in the northeastern Pacific and the West Coast of North America that dominated the winter has broken down, and a massive upper-level trough will move into western North America on Tuesday (-PNA), triggering pronounced upper-level ridge building in eastern North America and cold air quickly retreating later in the week. It is possible that a weak disturbance brings a little snow changing to rain, especially in northern areas, on Thursday as the cold air retreats, though any precipitation looks to be rather light and brief. Then, the upper-level trough and storm ejecting out of the Rockies will be quite strong, and there is amazing model agreement on the strength of the storm given that it is still several days away. Even with the slightly -NAO that is helping to keep some cold air before this storm, the storm will simply be too strong and mature too early, tracking well into northern Ontario and northern Quebec next weekend, leading to warm air just surging into the entire area with strong southerly winds next weekend, with perhaps a little rain on Friday with the initial warm advection. There could even be a line of thunderstorms with the cold front later on Sunday or Sunday night.

Source: TropicalTidbits

Source: Climate Prediction Center

Cooler but not particularly cold early following week, another potential storm and/or warmup, then perhaps relatively cool afterward with possibility of late-season snow

Early the following week, after the storm in northern Quebec passes off to the east, it will turn cooler, but likely not very cold, perhaps just closer to average. By this point, the snowpack that was so deep just a couple of weeks ago will have mostly been obliterated, at least in the lower elevations. Also, another upper-level trough and associated storm is likely to enter western North America around this time, and if the storm is strong enough, would track into the Great Lakes, Ontario, and Quebec again, bringing another surge of mild air, though it is possible that it is weaker and tracks farther south, perhaps enough so to bring at least front end snow to northern areas. Beyond that, ensembles actually indicate that upper-level troughing could return to eastern North America, with modest upper-level ridging in western North America. Ideally for the cold air to really dive into the contiguous U.S. and push the storm track farther south for late-season winter weather and snow, we would have the upper-level ridge extend into the Yukon Territory or Alaska as well as have some high-latitude blocking, such as over Greenland. Without this, temperatures would probably still be a roller coaster, generally just closer to the climatological average, with the storm track too far north for snow. However, this is very far out, so it is uncertain, and it is quickly getting more difficult to get substantial snow at lower elevations with low-level warmth and the March sun angle. Any snow that does fall will also quickly melt.

Source: TropicalTidbits