Plain-language summary:
After a chilly morning this morning, it will rapidly warmup through Tuesday with mostly sunny skies, except for northern and northeastern areas on Monday, when some clouds and even a shower or thunderstorm are likely. A heat wave will affect all of the region on Tuesday and Wednesday and at least areas south of the U.S./Canada border on Thursday. It will likely turn somewhat cooler and stormier on Friday and possibly next weekend, though it will still be hotter than average, and a brief heat surge is also possible next Sunday. It will likely also be cooler early the following week before likely turning hot again by the end of June.
Meteorological discussion:
A cool Canadian high pressure moved in yesterday, bringing a direct shot of cool air into our region. Combined with clear skies and dry air, it was rather chilly early this morning for mid-June, mostly 40-50F (4-10C) and even down to freezing in isolated mountain cold hollows. However, this chill will be short-lived and rapidly turn into a heat wave over the next few days. The high pressure has moved southeastward to near the U.S. East Coast, no longer in a position to advect cooler air from the north. Instead, as the high pressure continues to push southeastward, expand, and strengthen slightly, it will promote sinking air and mostly clear skies over our region, and allow the strong June sun to quickly warm up the air mass starting today. It will also advect hot air from the west and southwest through Wednesday. The warm advection and a subtle mid-level disturbance will promote some clouds and maybe even a shower or thunderstorm in northern and northeastern areas early Monday, but that will quickly move eastward and allow for enough clearing for Monday to be already hot, up to 86F (30C) in lower elevations from Montreal on southwestward. By Tuesday, 500-hPa heights of 597-600 dam just to our south, around all-time records, will minimize any chance of thunderstorms despite highs reaching 95F (35C) in lower elevations with moderate humidity. Winds will be southwesterly but relatively weak, allowing for little upslope or downslope effects as well as a sea breeze to cool off coastal locations.
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| Source: TropicalTidbits |
By Wednesday, the warm advection will be done, with our region just in a broad region of very hot air and strong vertically stacked ridging. However, the ridge is so strong that it will pull tropical moisture and clouds from the Gulf of Mexico northward into the Mississippi Valley on Monday and Tuesday, and it is possible that some of that, mostly in the form of mid to high-level clouds, could then stream northeastward clockwise around the ridge into our region. Most likely, it will mostly have dissipated by then with the sinking air in the ridge, but it could also add just enough moisture to for some mid to high-level clouds in our region and/or initiate a few thunderstorms over higher terrain. Both of which would make temperatures fall just short of the hottest it could get, but otherwise, lower elevations can expect highs of around 95F (35C) again. It could possibly get even hotter if it is sunny, but even with the strongest sun of the year, it is still quite difficult to fully mix out an air mass that is so warm aloft down to the ground. Generally, the atmosphere needs a little help to realize the highest temperatures, such as compressional warming right ahead of a cold front and/or downsloping flow, and we won't have much of that on Tuesday and Wednesday due to being near the vertically stacked ridge with rather weak winds and the cold front being well off to the northwest.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
By Thursday, a cold front will be approaching from the north, but exactly when it will arrive (having to push into the extremely strong ridge) is uncertain. For now, it appears likely that areas northwest of the U.S./Canada border will be somewhat cooler due to the early frontal passage and associated clouds and showers/thunderstorms, while to the southeast, compressional warming ahead of the front as well as stronger westerly winds will actually promote more vertical mixing of warm air aloft down to the surface and potentially allow for even hotter temperatures approaching 100F (38C), especially southeast of the Appalachians from southeastern Vermont to southern Maine. By Friday, the cold front will have slowly pushed south of our region, with a weak Canadian high pressure building in just to the north providing northeasterly flow and cooler (though still above average) temperatures. The slow-moving front will promote scattered showers and thunderstorms, and given the heat and humidity, any storm could become severe, though ridging aloft could suppress areal coverage of the storms. By next Sunday, another storm pushing east or east-northeastward through the Great Lakes could push north of our region, allowing for another surge of intense heat and humidity with strong southwesterly flow. However, in this scenario, it will likely be somewhat cloudier with more showers and thunderstorms, limiting the intensity and duration of the heat. The storm could also be weaker and stay just to the south, allowing our region to be on the cool side of the storm with cooler temperatures, cloudy skies, and numerous showers and possibly thunderstorms.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
Early the following week, cooler Canadian high pressure will likely dominate for a few days, with a weak upper-level ridge over the Rockies associated with a weakly positive PNA for a short time and weak upper-level trough over eastern or Atlantic Canada bringing at least a temporary break from the heat and humidity. However, long-range ensemble models suggest that more troughs entering the Pacific Northwest will promote more ridging across the eastern U.S. by the end of June, allowing for it to heat back up in our region. This week's heat wave could be just the start of the very hot summer that all models and forecast agencies have been forecasting for.
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| Source: Climate Prediction Center |
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| Source: TropicalTidbits |
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