Plain-language summary:
After a mostly cloudy and unseasonably cool Sunday and Monday with a few scattered showers, it will turn dry and sunny at least through next weekend, with a warming trend to summerlike temperatures. However, nights will still be relatively cool. It will likely cool down somewhat for early the following week, before soon-to-be Tropical Storm Francine possibly leads to increased clouds and rainfall for the middle of the following week, though it could also stay to our southwest, in which case it will stay dry and warm back up.
Meteorological discussion:
A cut-off upper-level low passing just off to the north ushered in an unseasonably cool air mass for early September last night. Though the core of the rain and cold air will stay just to the north, it will still be mostly cloudy and unseasonably cool across the region, with most places staying below 60F (16C) except from southern Vermont to central Maine where westerly downsloping winds off the Appalachians will boost temperatures. The cut-off low will move to our northeast by tomorrow, but a weak disturbance on its southwestern side will bring a few showers to eastern Ontario and northwestern New York tomorrow afternoon, with it being sunnier and somewhat warmer tomorrow elsewhere. However, persistent westerly winds and clouds will prevent temperatures from dropping a lot at night, preventing any frost.
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| Source: TropicalTidbits |
By Tuesday, a pronounced warming trend to summerlike temperatures starts as the cut-off low moves farther to the northeast, and upper-level ridging builds in and surface high pressure settles near or just south of our region, allowing for a deep warm and dry westerly to southwesterly flow and clear skies to dominate. Although the PNA remains positive, the strong persistent western North American ridge for the first week of September it will be pushed farther east over central North America and extending into the Great Lakes this upcoming week by a trough entering western North America. The ridging will continue through next weekend, though the ridge center being just to our west will allow a cold front to likely arrive Friday or next weekend, preventing the hottest potential temperatures. Still, with the sunny skies, lack of rain, and drying ground, much unlike this past summer, many lower elevation areas could exceed 80F (27C) ahead of a cold front that would enhance westerly flow of warm, dry air and induce compressional warming. However, the influx of dry air with the current cold cut-off low and lack of any moisture return from the south (e.g. Gulf of Mexico or western Atlantic) means that humidity will remain rather low through next weekend, and nighttime temperatures will still be relatively cool, unlike on most summer days. A broad and weak low-pressure area currently in the Bay of
Campeche will likely strengthen into Tropical Storm Francine tomorrow, move north
and make landfall along the Gulf Coast as a hurricane, but the strong ridging will slow or block its northeastward movement, ensuring dry weather in our region through next weekend.
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| Source: TropicalTidbits |
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| Source: Climate Prediction Center |
By early the following week, the cold front likely would have passed, with cooler Canadian high pressure taking over, causing temperatures to fall back to near or just above average, though any supply of true cold air will remain far to the northwest due to the overall ridging continuing in eastern North America. However, as any surface high pressure moves into the western Atlantic or Atlantic Canada shortly afterward, a weak southerly or southeasterly flow will result that could finally allow the remnants of Francine to reach our region the middle of the following week, enhancing clouds, moisture, and rainfall. However, with the broad ridging dominating, there is no strong upper-level trough nearby to give a baroclinic boost and lead to excessive rainfall. It is also possible that the high pressure over the western Atlantic or Atlantic Canada is strong enough to completely block the remnants of Francine from pushing northeastward into our region, in which case it would stay dry and just get warmer again as the ridge slowly moves eastward and blocks any cold air from reaching our region. Possibly except any direct influence of Francine, broad ridging, above average temperatures, and relatively dry weather look to generally dominate for the foreseeable future, with a lack of truly chilly cold spells.
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