Pattern change likely for Canada late next week

A significant pattern change may be in the works for Canada starting the second half of next week and going through the fourth week of August.

The persistent ridge of high pressure aloft that has been hanging out across the Northwest United States and western Canada is expected to retrograde over the northeastern Pacific Ocean starting around Aug. 18 or so. This will allow a series of troughs from Alaska to dive southeastward into western Canada, bringing cooler air to the region. The mean position of the trough being over the Canadian Rockies will likely mean that the bulk of the precipitation will be from the Rockies on east into the Prairies, which could certainly use the moisture.

On the flip side, this will likely translate into a strengthening ridge of high pressure aloft over eastern Canada and specifically Quebec, which may lead to an extended period of hot and drier weather with the potential for record high temperatures.

This pattern may linger through a good part of the remainder of August. Forecast pattern confidence is below average at this point for the first week of September as signals are weak by then with no indications of any significant ridges or troughs. So take that third forecast panel (Sept. 1-7) with a grain of salt at this point.

This has been a terrible year so far for fires in Canada as the charts show below. Data goes through Aug. 4.