Plain-language summary:
After an incredibly cloudy, unsettled, and chilly week and even the whole month of May so far, it will be turning warmer, drier, and sunnier through Wednesday, after still some scattered showers today. It will then turn unsettled and cooler again late week into next weekend, with it likely being unseasonably chilly again for a couple of days, though it will likely not be as intense or persistent as this week. There will likely be more hot, sunny days with fewer cool, rainy days in early June after next weekend.
Meteorological discussion:
Still scattered showers today, then turning warmer, drier, sunnier through Wednesday
Much of the region, perhaps except central and eastern Ontario, has seen little or no sunshine for over a week. However, the persistent, slow-moving closed off upper-level lows that have been affecting our region during this time are slowly moving away. The storm is already weakening today, with clouds breaking at times allowing for some sunshine, unlike most of this week so far, though the surface heating and still abundant moisture will lead to modest instability and the formation of convective scattered showers, as opposed to the more winter-like steady light rain earlier in the week. As the storm continues to weaken and pull farther to the east, vertically stacked ridging will gradually build in from central Canada, leading to sunnier weather and a warming trend through Wednesday, with few if any showers, mainly over higher terrain, after today. While hot temperatures will occur over central Canada with this ridge, due to the still kind of upside down weather pattern and the very moist ground in our region due to the excessive rainfall so far in May, it will not get nearly as hot in our region, but temperatures will still reach near 77F (25C) in lower elevations on Wednesday afternoon.
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| Source: TropicalTidbits |
Cool and unsettled weather returns late week into weekend, but likely not as intense and persistent as this week
Yet another upper-level low will close off early week in the central U.S. underneath the ridging building in across the Great Lakes and central Canada. This upper-level low will move into our region Thursday or Friday, depending on the timing, which is always uncertain with slowly-moving upper-level lows. This will bring more showers, though it does not appear to be as strong or have as much cold air as this week's storms. By next weekend, this upper-level low will likely interact with another upper-level trough diving from Hudson Bay, aided by the PNA climbing to near zero and upper-level ridging building in western North America. This combination of upper-level troughs or lows will bring yet another period of a few days of cool, unsettled weather in our region. However, with the high-latitude blocking mostly disappearing (NAO back up to near zero), and the northern trough actually bringing a stronger northern jet stream to push systems eastward, it appears unlikely that the cool, unsettled weather will persist as long as it did this week.
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| Source: TropicalTidbits |
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| Source: Climate Prediction Center |
Possibly hotter, sunnier early June after next weekend
As is always the case in the long-range, the weather pattern becomes more uncertain afterward. However, there are signs of the PNA dropping below zero again, leading to at least occasional upper-level troughing in western North America that would promote a downstream upper-level ridge in eastern North America. With the lack of high-latitude blocking to promote slow-moving cut-off lows underneath the block, and the weakening of the southern jet stream producing the southern cut-off low track, it appears less likely to continue to get cut-off lows, with hotter, sunnier days being more common and cool, rainy days being less common, though any heat will likely still be tempered by the still moist ground.
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