I don’t see prolonged big heat, but looks like pattern has changed to be more conducive for “pieces” of the big heat in the west to move east. At the same time, def some cooler airmasses modeled in Canada in the extended. IMO generally speaking, I see a pattern of 1-3 days of heat, couple days of seasonable weather and repeat for end of July / first half of August. I agree with the heat getting shunted more to the south and being more prolonged below our latitude.
If there will be a more prolonged stretch of Hot weather, I think it is more likely mid-late Aug and from the WAR.