Changeable but rather benign weather pattern this week; colder tonight, then warmer and showery early week, then colder with possible wintry mix late week before turning drier

Plain-language summary:

 

Tonight will be chilly, with widespread sub-freezing temperatures, especially north of the U.S./Canada border. A storm will quickly pass to the north later Monday into Tuesday, bringing warmer temperatures and light rain, except with it starting as snow in parts of eastern Quebec and northern Maine. It turns colder again for Wednesday, but another weaker storm will likely arrive on Thursday, possibly bringing a snow to ice to rain event to our region, but there is considerable uncertainty on this. It turns colder for the weekend and early the following week with possible occasional light snow, and then possibly warms up and stays dry afterward.

Meteorological discussion:

A weak cold front is passing through the region this afternoon. A cold high pressure over Quebec will lead to sub-freezing temperatures for most of the region tonight, especially north of the U.S./Canada border. However, the southeast U.S. ridge will prevent the coldest air from drilling farther south, and a low-pressure system tracking into the Great Lakes region and then northeastward into central Quebec will quickly usher in warmer air from the southwest later Monday and into Tuesday. Given the strength of the low-pressure system, it will be quite breezy Monday night into Tuesday, though given the mostly westerly flow cut off from deep Gulf of Mexico or Atlantic moisture and the best dynamic forcing remaining to the north, rainfall amounts will be rather light. Precipitation still likely start as snow Monday night in the normally colder areas of eastern Quebec and northern Maine.

 

Source: TropicalTidbits

 

Another cold high pressure will move into central Quebec on Wednesday behind the storm, but once again, the southeast U.S. ridge will limit the southward progression of cold air. Another storm will quickly move into the Great Lakes and then into eastern Canada or New England on Thursday, but there is considerable model disagreement on the strength, structure, and location of the storm. The GFS has been insistent for the past few days on a stronger storm cutting into Ontario and Quebec, bringing in warm air aloft quickly. In this scenario, given the inevitable low-level cold preceding the storm, there would be brief period of snow that turns to ice and then rain, given the deepening warm layer from above. Icing could last longer in the St. Lawrence Valley due to the classic channeling of low-level cold air from the northeast and in northern Maine due to cold air damming. However, most other models show a weaker storm, perhaps elongated or even split in two, that would bring less warm air and also less precipitation, with some light snow in northern areas and a wintry mix in southern areas. The ICON even shows a disturbance following shortly behind being stronger and bringing snow to the region on Friday, though this is also an outlier solution. There are many moving parts to this setup, most of which are still in the Pacific Ocean, and we will probably not have much clarity on specifics until all the pieces are on the North American continent by Tuesday morning, when they can be better sampled by the radiosonde network that is only present over land. However, given the rather fast zonal flow and lack of any deep troughs and ridges, a truly major or slow-moving storm is very unlikely.

 

Source: TropicalTidbits

 

Source: TropicalTidbits

All models agree on a cooldown afterward for next weekend, as a broader cold high pressure encompasses eastern Canada. This will bring mostly dry weather, though light snows could occur with any weak, moisture-starved disturbances in the flow. The deep-layer westerly to northwesterly flow favors below-average temperatures but also a relative lack of precipitation for the first half of the following week, with it possibly warming up afterwards if the ridge in the central U.S. expands eastward. With the AO turning more positive and NAO turning slightly positive, the plentiful supply of cold air nearby will get more and more restricted to higher latitudes, likely leading to above average temperatures dominating and any precipitation mainly falling as rain. This is despite the slightly positive PNA that would otherwise favor colder temperatures in our region.

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center