A cold front will bring an end to the recent warmth and stall, bringing a soaking rain to most of New England, except eastern Maine, and southern and central Quebec through Monday, while it dries out farther west by this evening. Afterwards, an unusually slow-moving pattern, perhaps most common in spring, associated with low-level moisture and cold air aloft will lead to generally below average temperatures and some showers, even snow showers at higher elevations, especially in the afternoon when breaks of sun lead to warming. Clearer and somewhat warmer weather returns for Thursday night through Saturday with frost and freeze potential for normally colder locations. By next Sunday or Monday, another slow-moving storm will lead to a return to showery and cooler weather. Throughout the whole pattern, no exceptionally cold or warm temperatures are expected, with an unusually little temperature variation. This pattern will likely last through at least the beginning of May, with perhaps it turning warmer and clearer afterward.
Meteorological discussion:
Yesterday’s warmth in parts of eastern Ontario to the western Adirondacks will be the last in a long time. A strongly negative NAO pattern and high-latitude North American blocking will force slow-moving troughs to dig underneath across the central and eastern U.S., especially since a ridge will be building across the Pacific Northwest, a rarity since November. The extensive blocking will actually cut off most of the true arctic air from reaching the contiguous U.S., so no extreme chill or hard freezes are expected, but below-average temperatures, mostly during daytime, will still dominate due to mostly cloudy skies, showers, and cold air aloft. The troughs will also block any true warm surge from the southern U.S., leading to an unusually small variation in temperatures for the foreseeable future, a contrast to the recent roller coaster. These slow-moving troughs do tend to be most common in the spring, as the jet stream weakens and retreats north, and it is easier for storms to get cut-off underneath it.
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| Source: TropicalTidbits |
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| Source: Climate Prediction Center |
To start, a cold front is stalling over New England through tomorrow and is oriented SSE-NNW, leading to persistent rain from southern New England up into southern and central Quebec. A weak low pressure will also form along the front. Given the relatively weak dynamics, excessive rain is not expected, though some heavier rains could fall on southern facing slopes of the Laurentians and White Mountains due to upslope enhancement. Eastern Ontario and northwestern New York will mostly dry out by this evening, leading to some clearing and slightly warmer daytime temperatures for Monday. Eastern Maine will also remain relatively dry as the front stalls to the west. The front will finally weaken and push to the east by later Tuesday, leaving the closed upper-level low and cold air aloft over the region. With some clearing, daytime temperatures will rebound somewhat, but this will also lead to some instability with the cold air aloft and residual low-level moisture, leading to some afternoon showers and mostly cloudy skies overall. Higher elevations will even see snow showers, though accumulations are unlikely except on the highest elevations.
Source: TropicalTidbits
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| Source: TropicalTidbits |
Another disturbance rotating around the broad upper-level low will bring enhanced showers to eastern Ontario and northwestern New York Wednesday and northern New England and southern and central Quebec Wednesday night. Then, by Friday, the upper-level low will have weakened with weak surface high pressure returning, leading to more clearing and sunshine and fewer showers, especially farther north, away from the influence of another storm over the mid-Atlantic U.S. With the sun, temperatures will actually be close to average or perhaps even a bit above average in Quebec, with relatively light winds. Frosts or freezes could occur at night with the clearer skies, though the low-level moisture enhanced by the wet ground may prevent this from being widespread in the Champlain and St. Lawrence Valleys.
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| Source: TropicalTidbits |
By next Sunday or Monday, another slow-moving, closed upper-level low, aided by the block, will move into the region, sparking more showers or possibly steadier rain and leading to cooler than average temperatures again after a brief warmup. However, the storm track and intensity is highly uncertain. Strong winds will also occur if the storm strengthens quickly. After that, the block could weaken somewhat, and a trough could approach the West Coast by the middle of the following week. If this occurs, the slow-moving troughing pattern will gradually fade, and warmer and less showery weather will return by early-mid May. Given the West trough/East ridge pattern that has dominated since November, I am skeptical that the cool pattern will last in our region for very long.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
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