After a cool June and early July, classic "dog day of summer" weather to dominate for 2nd half of July with summer heat, humidity, and thunderstorms

Plain-language summary:

After a cool June and early July with little humidity, a hotter and more humid weather pattern is emerging for this weekend into next week at least. Above average temperatures are expected on most days through the end of July, which would mean several hot days during the hottest time of the year, though record heat is not expected for now. There will also be more frequent chances of showers and thunderstorms next week, some of which could be strong, than we have seen so far this summer.

Meteorological discussion:

For the last month and a half, northern New England and southeastern Canada have been some of the few areas in North America seeing mostly below average temperatures. This was mostly due to an unusually persistent, semi-permanent trough that set up over Quebec and Labrador, leading to broad northwesterly flow out of Canada which has led to an unusual lack of heat and humidity, at least for recent years. Although strong ridging led to extreme heat building in most of the Plains and southern U.S., the Quebec/Labrador trough has blocked the heat from reaching our region. Most areas have had only one or two days above 86F (30C), except in southern areas which were further from the trough and had downsloping flow off the Green and White Mountains to boost temperatures on some days.

Source: NOAA PSL

However, the trough over Quebec/Labrador is finally weakening. It will still try to return occasionally, but it will not be as intense or as frequent as before, allowing ridging from the Plains to expand to the East Coast at times and hot weather to expand into southeastern Canada, with widespread 86-90F (30C-32C) highs by Sunday in lower elevations. It has also been relatively dry across the Northeast U.S., which could boost temperatures with the Sun's energy going into heating the air instead of evaporation. Humidity will be low to start with this weekend, but a disturbance on Monday will bring clouds and showers from west to east. This will make Monday cooler but also more humid for some especially in northern New York and eastern Ontario which will see clouds and showers all day, whereas areas to the east stay likely stay clear until early afternoon.

Source: TropicalTidbits

Sunday through Tuesday will likely be the hottest north of the U.S./Canada border, and Tuesday through Thursday will likely be the hottest to the south. Tuesday's heat will be widespread, but a cold front dropping from central Quebec could limit most of the heat on Wednesday to south of the U.S./Canada border. The front will stall out and slowly lift back north as a warm front later Wednesday into Thursday ahead of the next system entering the Great Lakes. Areas that stay south of the front will be even hotter on Wednesday and Thursday than on Tuesday, with the southwesterly flow bringing air out of Texas, which has been extremely hot this summer. In these areas, temperatures could approach 95F (35C), though there is uncertainty in this since it is still several days away. However, the lack of strong ridging will likely prevent record highs from being approached, especially since this is climatologically the hottest time of the year anyway.

Source: TropicalTidbits

The hot, humid air along with proximity to fronts will increase the chances of showers and thunderstorms next week, some of which could be strong to severe, something that has been almost absent this summer. Though a relatively weak cold front follows on Thursday, ridging will then develop in the western Atlantic or eastern U.S. and the associated westerly or southwesterly flow will likely bring temperatures back above average by the following weekend.

Source: TropicalTidbits

 

Source: TropicalTidbits