Plain-language summary:
Today will be a dry day across our region but with low clouds still dominating along and northwest of the Appalachians. After a brief clearing this afternoon into tonight, it will turn breezier with a several-hour period of light to moderate rain Monday afternoon and evening. The wind will persist on Tuesday with more clouds and seasonably cool temperatures. A very changeable weather pattern typical of November will then ensue, with frequent disturbances and fronts bringing clouds, precipitation, and temperature swings that will likely help continue to ease the drought at least slightly. Rain and very high-elevation snow is likely late Wednesday into Wednesday night, especially along and south of the U.S./Canada border, before coldest air mass of the season so far arrives Thursday into Friday. It warms up with rain likely next weekend before it turns colder with possibly the first chance of widespread snow early the following week before it turns even colder before warming back up.
Meteorological discussion:
Cloudy skies persist today, then brief clearing this afternoon into tonight before rain Monday afternoon and evening and staying cool but not too cold through Wednesday
Despite the big storm that brought heavy rain to our region on Thursday and Friday being long gone and way off to the northeast, with higher surface pressure slowly nosing in with no precipitation, low clouds continue to dominate much of the region along and northwest of the Appalachians. This is very common in November as all the moisture picked up by the unfrozen Hudson Bay and lakes and rivers across southern and eastern Canada gets trapped underneath a low-level and subsidence inversion while the sun angle is too low to break up the clouds. However, these clouds will gradually go away briefly this afternoon into tonight from west to east as stronger dry westerly to southwesterly flow takes over tonight before another disturbance/low-pressure system traveling into Quebec on Monday brings breezy conditions and a several-hour period of light to moderate rain in the afternoon and evening to our region ahead of a diffuse cold front. The cold front will maintain the cool air mass in our region, but once again, the air is not that cold as there is little connection with the Arctic, and Arctic Canada is still much warmer than average for this time of year. Also, the flow will be mostly out of the west, leaving more time for modification of the cold air mass, instead of a direct and stronger cold shot from the north. There will likely also be a fair amount of low-level clouds again, as well as a strong breeze, typical of November.
Rain and high-elevation snow later Wednesday into Wednesday night, coldest air of season Thursday into Friday
With the NAO turning positive, high-latitude blocking disappearing, and the mid-latitude jet stream strengthening and pushing south into our region more often, we will enter a more changeable weather pattern with disturbances and fronts crossing our region every few days. With the big rainstorms over the past 2 weeks, and these future disturbances bringing clouds and at least light precipitation rather frequently with relatively cool temperatures, and the low sun angle leading to low evaporation, the drought will likely continue to ease at least slightly. Another low-pressure system will strengthen as it crosses our region later Wednesday into Wednesday night, bringing another period of light to moderate rain for most of the region, though exactly who gets the most rain depends on the strength and location of the storm, which is still a bit uncertain. For now, areas just south of the U.S./Canada border look to get the heaviest rain. Given the marginally cold air, high elevations above 2000' (600 m) could see wet snow. A more direct and stronger shot of cold air, the coldest of the autumn so far, from the north or northwest will follow Thursday into early Friday. The colder and drier air with relatively high surface pressure will likely lead to more clearing and give the first freeze to anybody who hasn't yet seen a freeze. Many areas will likely drop below 25F (-4C), which is not exceptional for early November but would be notable this year given the lack of really cold air masses in Canada thus far.
Changeable weather pattern with warmup with rain next weekend, then cools down with first chance of widespread snow, then warmup
The surface high-pressure system will quickly move off to the east and be replaced by a low-pressure system moving into central Quebec, well north of our region, next Saturday, leading to breezy southerly winds, a notable warmup, and some rain. However, this will quickly be followed by a cooldown afterward and perhaps another weaker disturbance/low-pressure system for the following Monday or Tuesday. This second system will likely track farther south, leaving our region possibly north of the low-pressure center and on the cold side of the storm. The cold air and farther south storm track is aided by a +PNA and associated upper-level ridging in western North America and troughing in eastern North America, with the NAO and AO both decreasing to slightly negative, aiding in the cold air pushing southward into our region. Depending on how these systems interact and which one is stronger, this second system could provide the first real chance of widespread snow for our region, though the cold air available probably isn't strong enough yet for a big snowstorm and would favor a wet snow with some melting. Even colder arctic air could follow for a couple of days before the +PNA likely breaks down, with more upper-level troughing in western North America and ridging in eastern North America, leading to a warmup and end of any winter preview.
No comments:
Post a Comment