Pattern shift to bring much hotter, sunnier, and drier weather through at least Friday with moderate humidity; rainier again but with mugginess and continued summer warmth afterward?

Plain-language summary:

 

After another chilly day today for most, especially from Vermont eastward, it will turn much warmer and drier for next week, especially for northern areas and away from the coast. It will be more humid than the last hot spell at the beginning of June, which may lead to slightly cooler daytime temperatures but warmer nights. More clouds and rain could arrive next weekend, but the timing is uncertain, and if it does occur, will be accompanied by mugginess without any true chill. Summertime warmth and humidity is expected to prevail afterwards as well, with occasional to frequent chances for showers and thunderstorms.

 

Meteorological discussion:

 

Today will be the last chilly day for most of the area. It will be especially pronounced from Vermont on eastward, where it will still be cloudy and chilly (highs in 50s and 60s F or 10-20 C) under the influence of a low pressure over western Nova Scotia slowly pulling off to the east. Over eastern Ontario and northwestern New York, more sunshine will lead to much warmer temperatures than yesterday, although still below average.

 

Source: TropicalTidbits

 

By Monday afternoon, the clouds will mostly dissipate as the storm and lingering shortwaves will be gone. However, weak easterly flow will still lead to subtle cool advection east of the Appalachians, especially in Maine, from the departing storm over Atlantic Canada. West of there, temperatures will be closer to average. The reversed meridional temperature gradient that has been unusually frequent since May will return as an upper-level ridge with hot, dry, and sunny weather builds southeastward from northern Ontario, with a slow-moving upper-level low underneath over the southern U.S., bringing cool, cloudy, and rainy weather. The upper-level ridge will be aided by an unseasonably strong upper-level trough in western North America with a -PNA and the breakdown of the high-latitude blocking and associated -NAO. Given the recent wet weather in northern New England, the now wetter ground will lead to more evaporation and higher humidity than during the last hot spell at the beginning of June. So although the skies will be mostly clear with relatively light winds, leading to relatively large day-to-night temperature differences, this additional moisture and perhaps resulting afternoon cumulus clouds may also prevent daytime temperatures from getting quite as hot, and also keep nights warmer. There could be a day or two where areas east of the Appalachians get especially hot due to a boost from westerly winds downsloping off the Appalachians if a subtle low pressure passes to the north. Otherwise, coastal areas will be cooler due to the weak synoptic-scale flow allowing for sea breezes. Also, areas north of the U.S./Canada border that have not received as much rain could be hotter.

 

Source: TropicalTidbits

Source: Climate Prediction Center

 

 

The upper-level low to the south will slowly weaken as it meanders northeastward into the Ohio Valley by Friday. Eventually, it could bring increased clouds, moisture, and rain to our area by next weekend, even in its greatly weakened state. However, the timing is uncertain, as these slow-moving closed upper-level lows are notoriously difficult to predict, both in speed and strength. With no cold air mass, it would turn muggy and cooler but not that cool. Although the trough in western North America with the -PNA will weaken and possibly revert to a weak ridge, the breakdown of the blocking pattern as well as the climatological shift of the jet stream to the north and erosion of cold air masses means that temperatures will likely remain near to above average, likely with humidity, with few if any chilly days like this weekend. This will also lead to opportunities for showers and thunderstorms with any disturbance that rolls through. Slight upper-level troughing over the Midwest U.S. or Great Lakes likely will lead to a deep southwest flow, bringing more moisture from the Gulf of Mexico, and combined with the instability, heavier convective rains are likely from time to time. The breakdown of the blocking pattern will also lead to less separation and distinction between the subtropical and polar jet streams that we have seen for the past month and less of an area of weak winds in between.

Source: TropicalTidbits

Source: TropicalTidbits