Very amplified weather pattern to start prolonged period of early winter like weather; first widespread snow for most today through Tuesday; more snow and rain showers for northwestern areas Wednesday; drier but still chilly Thursday through next weekend with potential for more minor storm with snow early following week; uncertain afterward but probably persistent modest chill with occasional chances for snow or mixed precipitation

Plain-language summary:

 

A very amplified weather pattern will favor a persistent early-winter like weather pattern with persistent modest but not extreme cold and several opportunities for snow or mixed precipitation. Many areas will see snow today into tonight with an initial primary storm, marking the first widespread snow of the season, though it will quickly change to rain along and southeast of the St. Lawrence Valley with a narrow area of 6-10" (15-25 cm) to the northwest over eastern Ontario and the Laurentians. Any rain will change back to snow tomorrow evening for Vermont and southern/eastern Quebec, though it is still not clear how much if any precipitation there will be then as a second storm develops. Snow showers will linger along and northwest of the Appalachians into Tuesday before another disturbance brings light snow and rain showers along and northwest of the St. Lawrence Valley, perhaps enhanced by lake-effect precipitation off Lake Ontario into eastern Ontario and the Laurentians. It will turn drier but stay chilly Thursday into next weekend, with another more minor storm possible early the following week that could bring more snow if the storm track is right. There is uncertainty in the weather pattern afterward, but it seems likely that pushes of warm air from the southwest will be blocked, with a persistent flow of modest cold from the north and northwest into our region continuing, leading to more potential for wet snow or mixed precipitation if any storm arrives into our region.

 

Meteorological discussion: 

 

While our region escapes extreme cold, still first taste of winter with first widespread snow for most and narrow area of heavy snow in eastern Ontario and Laurentians today into tonight 

 

With a +PNA, -NAO, and -AO all conspiring together to produce a very amplified upper-level ridge in western North America and trough in central and eastern North America. Such a weather pattern favors a northerly flow from the Arctic all the way to the Gulf of Mexico, with temperatures at least aloft being among the coldest ever recorded for this time of year in the U.S. Deep South. Our region will not receive the core of the cold air, but will still have the first taste of winter today into tonight with a slowly strengthening storm pushing into upstate New York and then northern New England this evening producing snow on the northwestern side with enough cold air in place. The first injection of cold air arrived just in time last night with a little extension of cold surface high-pressure system over central Quebec leading to a direct shot of cold air from the north with minimal modification over mid-latitudes and the Great Lakes. This means that precipitation ahead of the main storm will fall as snow for almost everyone except southern Vermont to central/northern Maine, marking the first widespread snow of the season for most, even at lower elevations. Still, temperatures will be relatively marginal as is usually the case in early November, and warm advection will easily change any snow to rain along and southeast of the St. Lawrence Valley this evening, with the heavy snow of 6-10" (15-25 cm) occurring in a narrow area in eastern Ontario into the Laurentians where a narrow frontogenetic band of very heavy snow will sit for a few hours. A narrow area of ice pellets and freezing rain is likely mostly in northwestern New York, aided by the channeling of low-level cold air through the St. Lawrence Valley, but given that the low-level cold isn't particularly strong as it is early November, the areal extent and magnitude of any icing will be relatively minor.

 

Source: TropicalTidbits

 

Source: TropicalTidbits

 

 

Source: Climate Prediction Center

 

 

Some backside snow/snow showers Monday evening into Tuesday; another disturbance with light snow/rain showers on Wednesday along and northwest of St. Lawrence Valley

 

The main system will move into eastern Quebec by Monday, but a secondary system will develop and strengthen along the U.S. East Coast and move almost due northward, a symptom of the very amplified weather pattern. An area of precipitation will develop on the western side, likely over Vermont, New Hampshire, and southern and eastern Quebec, with any rain changing back to snow as cold air slowly filters in from the west. While rain changing to snow usually does not amount to much, the strong upper-level dynamics may be enough to lead to a burst of snow for a few hours from Vermont into central Quebec. This is a rather tricky situation with models still disagreeing on just how pronounced this backside precipitation will me. Regardless, snow showers will then continue along and northwest of the Appalachians into Tuesday as the system joins into a occluded, broad, and strong cyclone over northeastern Quebec on Tuesday. Colder air will also filter in from the west but will be modified as it is not directly from the north, and eventually, winds will turn to southwesterly by Wednesday as another disturbance moves through which will produce light snow and rain showers, possibly enhanced by lake-effect bands off the Great Lakes, including a band off Lake Ontario extending into eastern Ontario and the Laurentians. Given how far north the disturbance is, almost all the little precipitation that will fall will be confined to the St. Lawrence Valley on northwest.

 

Source: TropicalTidbits

 

 

Dries out with at least partial clearing Thursday into Saturday with another shot of chilly air; possibly another system with uncertainty in precipitation type early the following week

 

The weather pattern will then slowly de-amplify and move eastward as an upper-level trough moves into the western U.S. (+PNA turning to neutral or slightly negative) triggering an upper-level ridge to build downstream in the central U.S. However, behind Wednesday's disturbance, the wind will turn back to the west and then northwest, with a surface high-pressure building in from northern Ontario, providing drier weather and another shot of chilly weather through next weekend, though it won't be true arctic air. Also, the -NAO and -AO and associated high-latitude blocking will remain, and combined with an upper-level trough stuck underneath over Atlantic Canada, the deep northwesterly flow will prevent most or all of the warmth building in the central U.S. from entering our region. The surface high-pressure could lead to some clearing of clouds at least before a disturbance could move southeastward from northern Ontario to our region early the following week, and it could be cold enough for more snow depending on the storm track, even though southeastward moving storms like that do not carry a lot of moisture due to the lack of deep southerly flow of moisture from the Gulf of Mexico or western Atlantic. The storm could also be suppressed to the south, leaving our region dry, if the blocking pattern is too strong.

 

Source: TropicalTidbits

 

 

Uncertainty in weather pattern after next weekend, but possibly persistently modestly chilly with occasional wet snow or mixed precipitation opportunities 

 

Beyond next weekend, there are conflicting signals in the weather pattern. The near-neutral or slightly negative PNA would promote slight upper-level troughing in western North America and ridging in eastern North America, which by itself normally would favor warmth in our region, but in this case, the high-latitude blocking (-NAO and -AO) as well as trough in Atlantic Canada will also be persistent and attempt to thwart any warmup coming from the southwest, especially if Canadian surface high-pressure systems across Ontario and Quebec continue to dominate and promote more northerly instead of southwesterly flow. Yet if there is a strong enough storm ejecting out of the Rockies that moves northeastward, our region will eventually get into the warm sector with southerly or southwesterly flow. As such, there is considerable uncertainty in the temperature pattern, but it appears that our region could be one of the few in North America to see sustained near-to-below average temperatures, mostly a result of persistent chilly but not particularly cold weather with a lack of true Arctic air and most of the cold air still being in northern Asia with anomalous warmth still dominating over northern Canada. This is occurring while the southern and central U.S. becomes persistently warm. The neutral or slightly negative PNA could also allow for storms ejecting out of the Rockies to reach our region instead of being suppressed to the south, and with surface high-pressure to the north delivering at least modest cold air, there could be more opportunities for wet snow or mixed precipitation with temperatures likely to be marginal with any event given the lack of true arctic air and that it is still only mid-November at that time. Suppression of storms is also a possibility, leaving our region relatively dry.

 

Source: TropicalTidbits