Plain-language summary:
After a cool shot yesterday, it will be briefly warmer today before it rains tonight and then turns much cooler from tomorrow through Thursday. It will be relatively dry during this stretch, though it could be rather cloudy at times, and scattered showers are possible on Tuesday and Wednesday night. Some normally colder locations will likely see a frost or freeze at some point on any clearer night. Clouds will clear on Friday, and then it will likely briefly warm up next weekend before turning cooler again for the following week. The weather pattern overall favors rather dry weather in from the central U.S. to southeastern Canada, including our region, for next week and beyond.
Meteorological discussion:
After a cool shot yesterday, and the coolest night since mid-spring last night, it will warm up briefly today with strengthening southerly winds ahead of a low-pressure system entering western Quebec, with a potent cold front stretching to the southwest. The cold front will plow through the region tonight into early tomorrow with a period of light to moderate rain, and it will dry out later tomorrow with a much cooler air mass. The associated upper-level trough will dive into eastern Canada, cut off, and move very slowly through Thursday, allowing the cool air mass to persist until then. This is perhaps not surprising given the ridge re-asserting itself over the western U.S. through Thursday (+PNA and the same ridge responsible for the record heat this month there), leading to a persistent downstream trough over eastern North America, especially with the -NAO and AO now. With the cut off low staying mostly to the north and then to the northeast, our region will experience mostly descending motion and dry air, limiting precipitation, though shortwaves could lead to some showers on Tuesday and Wednesday night. Even without showers, increased stratocumulus clouds will likely occur at least some days as they usually do with cooler air masses coming from the northwest in the fall. With the cooler air mass, and winds not being particularly strong, a frost and freeze will likely occur in normally colder locations on any clearer night, though that is unlikely in most of the broad St. Lawrence and Champlain Valleys, as well as urban and coastal areas.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
By Friday, the cut off low will have moved to the northeast, and with surface high pressure moving in, clouds will clear out and daytime temperatures will warm. The westerly flow on the southern and southwestern side of the cut off low/upper-level trough will also move Hurricane Milton (currently in the western Gulf of Mexico) eastward into the southwestern Atlantic, far to the south of our region. As a shortwave briefly breaks down the ridge in the western U.S., a ridge will briefly try to build into our region next weekend, likely leading to a brief warmup. However, the western U.S. ridge will likely quickly re-establish (PNA staying positive), with a trough dominating our region for the following week (negative NAO and AO still helping though not as strong). For now, ensembles are suggesting a persistent weather pattern mostly dominated by a broad ridge axis over the Rockies and a broad trough axis over New England. This will lead to a general west to northwest deep-layer flow of dry, continental air across the central and eastern U.S., leading to a remarkably dry period for a large part of the central and eastern U.S. and southeastern Canada, including our region. It will also allow for frequent pushes of cooler air from central and northern Canada into our region, with generally near to below average temperatures, though there is no sign of any extreme or record-breaking cold.
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