Plain-language summary:
After a rather cloudy and wet week, most of this week will be drier, except Tuesday evening through Wednesday. It will be mostly sunny but chilly in most of our region on Monday, with a widespread hard freeze Monday night. It will briefly turn milder and breezy on Tuesday before a widespread light rain falls Tuesday evening through Wednesday. It will turn much cooler afterward, with rain possibly changing to a short period of snow at the end of the storm Wednesday afternoon into Wednesday night, especially in higher elevations. It then turns drier and sunnier but remains chilly with hard nighttime freezes, though daytime temperatures will gradually warm up. The chilly pattern will likely end afterwards, with warm air trying to move in and battling with the preceding cold air mass potentially leading to a stormy and wet period for the following week.
Meteorological discussion:
After the frequent light rain events and cloudy skies over the past week, we are settling into a somewhat drier pattern due to northwesterly flow aloft prevailing. However, it will not be completely dry due to some disturbances riding in the northwesterly flow. It will be rather cool but mostly sunny today with a cool Canadian air mass in place, but this will be replaced by an even colder, arctic air mass on Monday behind a disturbance passing to the north over central Quebec brings a stronger cold front early Monday morning. Little or no precipitation will fall with the cold front due to the lack of moisture ahead of it, though some flurries are possible. The arctic air mass will mostly aim to the north of our region, with areas south of the U.S./Canada border only getting a glancing blow, but whatever part of the arctic air mass will come in directly from the north with the minimum possible modification. This will lead to a hard freeze for many areas north of the U.S./Canada border tonight and areas east of the Appalachians Monday night, even in the urban areas and broader valleys. It could have been even colder if the coldest air with lightest winds did not come during daytime. Even with full sunshine, the Laurentians may fail to reach 40F (4C) on Monday.
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| Source: TropicalTidbits |
The cold air mass will quickly move out as yet another disturbance moves to the northwest over northern Ontario on Tuesday and then into central Quebec on Wednesday. Like with tomorrow's system, this disturbance will be moisture-starved, but it will be stronger with colder air aloft promoting more instability and stronger dynamics to generate precipitation. The associated upper-level trough will also cut off into a closed low that will move into southern Quebec into our region later Wednesday. Ahead of it, it will briefly turn milder Tuesday afternoon, with breezy southerly or southwesterly winds, before rain showers overspread our region Tuesday evening and night. Models differ on the evolution afterward, but the GFS has consistently showed the closed off low remaining rather strong as it moves into our region and promoting a new surface low pressure over northern New England and the eastern Townships of Quebec later Wednesday, though it has started to back off on this solution. This would lead to temperatures rapidly falling later Wednesday, with cold air aloft and dynamic cooling from precipitation leading to rain changing to snow in most of the region, even in lower elevations. However, the GFS is an outlier for now, with most other models showing the closed low weakening and becoming detached from the coldest air mass, leading to little more than a quick cool down with some cold light rain at lower elevations and light snow at higher elevations at the end of the storm. Nonetheless, most areas along and northwest of the Appalachians, as well as northern Maine, will likely see at least some snowflakes flying, even if accumulations are limited to higher elevations.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
As a cold surface high pressure builds in for Thursday and Friday, it will turn drier and sunnier, with slowly warming daytime highs, while widespread hard freezes at night are likely. This chilly pattern is a bit odd given that the PNA remains slightly negative for the foreseeable future, though there will be a brief transient ridge in western North America on Tuesday. The neutral to slightly positive NAO indicates a lack of high-latitude blocking to slow systems down, though the slightly negative AO is promoting arctic air to more easily travel into the mid-latitudes.
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| Source: TropicalTidbits |
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| Source: Climate Prediction Center |
The chilly pattern likely will not last beyond next weekend. Another storm and associated upper-level trough moves into western North America late next week into next weekend. This will promote a ridge to build in the central U.S. into the Great Lakes region, allowing multiple days of deep southerly flow of warm, moist Gulf of Mexico to engulf most of the eastern U.S. This might occur too far west for our region to get into the warmth and humidity initially, with sneaky backdoor cold fronts still bringing cooler air masses into our region occasionally. However, as the warmth becomes stronger and more expansive, it will inevitably eventually reach our region the following week, perhaps in weakened form. As the warmth battles with the preceding colder air masses, we may have many frontal passages and stormy, wet days for the end of April.
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| Source: TropicalTidbits |
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