Plain-language summary:
Today will be hot and sunny with moderate humidity throughout the region and some mid to high-level smoke in northern areas. A previously unexpected coastal storm will produce much cooler temperatures and cloudy skies east of the Green Mountains tomorrow, though it will still be hot with some sunshine farther north and west but not as hot as earlier expected. Hot weather returns for the rest of the week, with mostly sunny and hot but not record hot weather, except for a couple of slow-moving disturbances bringing clouds and scattered showers and thunderstorms, such as on Wednesday, with slowly increasing humidity. It will very likely turn cooler for the following week. It is unlikely that we see a week this persistently hot again until at least next summer.
Meteorological discussion:
It is yet another sunny day across the region, with a bit of mid to high-level smoke from the western wildfires filtering out the sun a bit. Today is the hottest day in over a week for most, with widespread high temperatures approaching 86F (30C) at lower elevations. Humidity is only moderate due to the initial push of drier air on Thursday and the lack of rain or moisture advection since then. While this is the start of what was expected to be a heat wave earlier, a wrinkle has developed: a sneaky weak cut-off upper-level low offshore will promote a briefly strengthening surface low that will move northwestward into the eastern New England coast tomorrow before weakening and turning northeastward. The models have been incredibly consistent in bringing it closer and closer to our region for the past few days, leading to easterly flow off the Atlantic Ocean and widespread clouds east of the Green Mountains, along with scattered showers mostly in eastern areas. The clouds will keep temperatures below 75F (24C) in these areas. Areas to the north and west of the Green Mountains will still be partly to mostly sunny, with subtle downsloping from weak easterly winds perhaps being just enough to erode the clouds coming from the east, and with temperatures reaching near 86F (30C) at lower elevations, but even this is cooler than earlier expected due to the weak easterly flow not allowing for the really warm air mass from the west from entering. The upper-level low will also push the smoke to the northwest at least temporarily.
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| Source: TropicalTidbits |
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| Source: NOAA |
By Tuesday, the weak low-pressure system will have whisked northeastward into Maine and New Brunswick, leaving most of our region in mostly clear skies and hot temperatures again, except Maine, which will still be cloudy with a few showers in vicinity of the weak low-pressure system. Broad ridging will dominate almost the entire contiguous U.S. and southern Canada, but it won't be a completely clean ridge, with slow-moving weak and almost cut off disturbances perturbing the flow and preventing the strong westerly flow from the drier Rockies or Plains region needed to get true extreme heat. Humidity will gradually increase with no dry air mass to lower it back down. One weak disturbance will bring in widespread clouds and trigger scattered showers and thunderstorms Wednesday afternoon and evening, leading to a cooler day. A second weak disturbance could arrive Friday or Saturday, but models differ on the timing by over a day, likely due to its slow movement, and it could also pass to the south. Outside those disturbances, it will be mostly sunny throughout the week. The hottest day of the week depends a bit on the timing of various disturbances and would be a day with weak westerly flow and sunny skies, when it could reach 90F+ (32C+) in many lower elevation locations, though once again as mentioned earlier, the setup with weak disturbances perturbing the flow is not quite set up right for truly extreme heat.
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| Source: TropicalTidbits |
After Saturday, it will likely turn cooler as ridging consolidates in western North America (PNA turning slightly positive again) with NAO and AO turning slightly negative, allowing more troughs with cooler air from northern Canada to penetrate southward into our region. It will still be early August, and it is unlikely that the full force of the chilly air masses will come in initially, though northern areas will likely experience more of the cooler air masses, but it also appears unlikely that we will see the kind of long-lasting hot weather expected this week again until at least next summer. Average temperatures are starting to decrease, and the decline will become more noticeable, especially in the intensity of the cooler Canadian air masses, starting in mid-August.
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| Source: Climate Prediction Center |
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| Source: TropicalTidbits |
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