Plain-language summary:
After yesterday's Nor'easter capped off an incredibly wet and cloudy May, it will be still chilly and mostly cloudy today but with little or no rain, likely the last widespread unseasonable chill before summer weather dominates for the foreseeable future. It heats up quickly from Monday through Wednesday, with Wednesday being the hottest day of the year so far this year for most. Wildfire smoke will filter the sun somewhat on Tuesday and Wednesday. Chances of showers and thunderstorms return from Thursday to the weekend, though widespread heavy rain is not expected. It will also likely turn modestly cooler but not chilly for this period. It appears to be generally warm to modestly hot but not excessively hot afterward.
Meteorological discussion:
Nor'easter caps off incredibly wet and cloudy May; after chilly and mostly cloudy today, quick warming trend with plenty of sunshine through Wednesday
Yet another out of season Nor'easter brought more heavy rain to New England and southern Quebec, contributing to one of the wettest and cloudiest Mays on record in the area.
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| Source: Aviation Weather Center and NOAA |
Behind the Nor'easter, another surge of unseasonably chilly air is encompassing all of the Northeast U.S. and southeastern Canada, with most places along and north of Interstate 90 not even getting above 60F (16C), despite only scattered showers at most and even a little sunshine for many areas. However, unlike for most of May, the loss of high-latitude blocking (with positive AO and neutral to slightly positive NAO), and the Nor'easter being still connected to the main jet stream, means that the clouds and chill will quickly move off to the east over the next few days. Also, an upper-level trough entering the western U.S. (-PNA) will trigger the quick development of a downstream upper-level ridge in the eastern U.S., leading to sunshine and quickly warming temperatures through Wednesday. This likely starts a much more summerlike weather pattern for our region with above-average, though not excessively hot, temperatures dominating with no more long-lasting unseasonably chilly air masses. Wednesday will likely be the first day of this year to reach 86F (30C) for many lower-elevation areas and will likely be the hottest day in the next 10 days. One caveat is that the large area of wildfire smoke now covering much of the central U.S. that advected from the north (Manitoba), where many large wildfires have been burning, will be moving eastward into our area, possibly filtering out the sun enough to lower daytime temperatures slightly on Tuesday and Wednesday.
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| Source: TropicalTidbits |
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| Source: Penn State Meteorology and NOAA |
Chances of showers and thunderstorms return Thursday through next weekend with cooler but not chilly temperatures
Unsettled weather will return again on Thursday. A weakening and slowly-moving cold front will be traversing the region from northwest to southeast on Thursday and Friday, causing increased clouds, slightly cooler temperatures, and the chance of scattered showers and thunderstorms, especially in the afternoon and evening with sunshine-induced instability and increasing humidity. However, unlike the recent Nor'easters, the front appears weak enough to prevent any organized low-pressure systems from really strengthening, leading to only weak dynamics and rainfall coming mostly in scattered showers and thunderstorms, more typical of summer. Even behind the front, temperatures will likely still be at or slightly above average, though this depends on how widespread the clouds and any rain are. The specific details of any storm systems are quite uncertain for next weekend and beyond, but there appears to be a decent chance of next weekend being unsettled again with at least scattered showers and thunderstorms due to at least one weak disturbance traversing from west to east, continuing the theme of rainy weekends this spring and early summer.
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| Source: TropicalTidbits |
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| Source: TropicalTidbits |
Above-average temperatures likely prevail after next weekend with lack of chill or extreme heat
Despite the uncertainty starting next weekend, there is strong model signal for a trough to enter the upper Midwest U.S. and Great Lakes just after next weekend. For now, it appears that this will cause another warmup for a couple of days (though unlikely to be particularly hot) before the cold front and trough moves through, cooling it down at least modestly. The more westerly or southwesterly low-level flow that appears likely for now (as opposed to straight from the north) means that core of the cooler air will stay to the northwest this time. There are some signs of broad upper-level ridging generally prevailing in the eastern U.S. for the following week, a downstream response to slight upper-level troughing in western North America (-PNA). Combined with the continued absence of high-latitude blocking (neutral to slightly positive AO and NAO), persistent chilly, cloudy weather with slow-moving storms is unlikely. Excessive heat is also unlikely given how wet it has been lately not just in our region, but all across most of the eastern U.S. Also, since early June isn't the peak of summer yet, it would take very anomalously hot air to result in truly extreme heat in our region. Only parts of central Canada and the Midwest U.S. have been dry recently and could serve as source regions of occasional very hot days if we have deep westerly flow.
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| Source: TropicalTidbits |
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| Source: NOAA |
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