Plain-language summary:
It will be warm but not hot, dry, and mostly sunny through Wednesday with light winds, low humidity, and cool nights. It will not be as warm or hot as expected several days ago. It will turn cloudier and breezier on Thursday before substantial rain is likely on Friday to possibly Saturday, though the exact timing and amount of rain is still uncertain. It will turn much cooler for next weekend into following Monday, but not as chilly as farther west, with drier weather but some clouds and scattered showers still being possible. It will warm up and stay dry for a few days afterward, but warm and dry weather is unlikely to be sustained for more than a few days at a time, with at least occasional cooler air masses and opportunities for rainfall likely to start easing the drought, though the weather pattern could favor warmer than average temperatures overall.
Meteorological discussion:
Dry, warm, and mostly sunny through Wednesday with cool nights
After a cut-off upper-level low brought unseasonably chilly weather and more showers than expected on Friday and Saturday, a large Canadian surface high-pressure system, a familiar sight over the last month, has settled into the region, which will provide dry, sunny, and seasonably warm but not particularly hot weather through Wednesday. Isolated afternoon showers are possible in the higher terrain of southeastern Quebec and western Maine on Wednesday. Nights will be rather cool due to the dry air, clear skies, and lengthening nights, especially in the usual cold hollows away from urban areas. The warmup will not be as pronounced as models showed a few days ago due to the surface high-pressure system staying near or to the east of our region, which means that the winds will never turn southwesterly to westerly, which is necessary for the advection of hot air from the western and central U.S. into the currently still slightly cool air mass behind the big cooldown earlier in the week.
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| Source: TropicalTidbits |
Breezier and cloudier Thursday, potential major rainfall Friday, much cooler and mostly dry next weekend
It also appears as if the upper-level ridging along the North American West Coast extending all the way into Alaska will be stronger and more persistent than originally expected. All-time September high temperature records could be broken in British Columbia and the Northwest U.S. Interestingly, it is too far west to register as a +PNA, with the PNA actually being slightly negative. At the same time, a downstream trough will deepen and become unseasonably strong for the beginning of September as it plows southeastward into the Great Lakes by Thursday, eventually closing off into a broad, closed upper-level low that meanders northeastward into Quebec and slowly weakens by next weekend. Also a bit surprisingly, the weather pattern is configured such that it does not really register as a -NAO or -AO, perhaps due to the lack of true high-latitude blocking despite the rather amplified weather pattern.
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| Source: TropicalTidbits |
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| Source: Climate Prediction Center |
Our region will initially be on the eastern side of the trough, leading to strengthening southerly flow which would bring modified marine air from the western Atlantic instead of true hot and humid air from the southern U.S. or Gulf of Mexico. It will also turn cloudier with some showers possible in the upslope areas in the southeastern slopes of the Adirondacks and Green and White Mountains. A cold front will first pass early Friday, bringing a period of showers and possibly scattered thunderstorms, though meager instability should prevent any storms from becoming too strong. Then, late Friday into possibly Saturday, a disturbance rotating around the Great Lakes cut-off low will spawn another low-pressure system closer to our region, strengthening and tapping Atlantic moisture to likely produce at least moderate rainfall for someone, perhaps the most widespread substantial rain in over a month. However, models disagree on the exact timing and strength of the system, and it is possible that it is too weak and far north to produce much rain for our region. That system will move to the northeast by Saturday night with even cooler air behind it, though the cold air will not be as pronounced as in the Midwest U.S. due to the trajectory of the cold air first going into the Midwest U.S. and then getting modified as it moves east and northeastward into our region, as opposed to coming directly from the north or northwest. That tends to happen a lot in the fall and early winter. It will also likely dry out as well, though perhaps with some clouds and scattered showers due to the cold air aloft triggering low-level instability, especially during the daytime.
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| Source: TropicalTidbits |
Warming up again for following week, but likely not for very long, with at least occasional cooldowns and rainfall chances expected
After next weekend, the closed upper-level low will push farther northeastward, allowing for a Canadian surface high-pressure system to move into the eastern U.S. on the following Monday, perhaps briefly turning the flow enough to the northwest for a more direct and therefore stronger cold shot. But shortly afterward, the surface high-pressure system will move to our southeast, allowing for several days of dry, mostly sunny weather with southwesterly flow and a warming trend for the following week. However, sustained warm and dry weather appears unlikely given the upper-level ridging in western North America is not likely to truly reverse (though occasional troughs are possible) and the mid-latitude jet stream strengthening and making its seasonal progression southward into our region. This would lead to at least occasional, if not frequent, cold fronts and opportunities for at least some rainfall, even if the tropical moisture for producing torrential rains is lacking. The tropical Atlantic is very quiet right now for being close to the climatological peak of the hurricane season, but even with any tropical storms or hurricanes that do develop in the long-range, the troughs, usually accompanied by strong westerlies aloft, moving into our region will likely make any tropical storms or hurricanes that turn northward to then turn eastward away from our region. Unlike many recent years, summer appears to have ended early around a week ago, not long after the incredible heat in mid-August. The drought will likely stabilize or ease a bit with the cooler weather and increased chances of rain; droughts typically do not last very long in our region. Still, models actually do show temperatures being above average in the net sum after next weekend with the West ridge/East trough easing at least somewhat, even if true summer heat and humidity is unlikely to return.
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| Source: TropicalTidbits |
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