A large area of Arctic air will continue to expand deep into the central and western U.S. into the weekend. The image below shows the projected temperature departures in F. for early Friday with a large area have temperatures at least 30 F. or 17 C. below normal.
The main reason for this sustained push of very cold air is the strong upper-level high that has been sitting just south of Alaska (see below)...
The combination of wind and very low temperatures will make it feel dangerously cold tonight across portions of the southern Prairies and into the northern U.S. Plains.
There will likely be additional waves of Arctic air spilling down into northern BC and the Prairies through the middle of the month.
Potential wintry mix Sunday night into Monday in the East
Strong energy dropping into the Southwest U.S. this weekend will help draw a wave of low pressure up toward the Great Lakes Sunday night into Monday.
The track of this primary storm would normally allow milder air to be drawn northward into Ontario and Quebec. However, in front of this storm will be an Arctic high pressure system that will not easily back down and thus there is the potential for accumulating snow spreading up through southern Ontario Sunday night then into Quebec and New Brunswick on Monday.
Eventually, enough "mild" air may work in aloft to change the snow over to sleet or freezing rain, especially from SW Ontario through the Saint Lawrence Valley with the potential for a sustained period of ice or sleet.
My suspicion at this point is that the bulk of the steadier precipitation out in front of this storm will be in the form of snow for most of eastern Canada and as the precipitation gets lighter it turns to sleet or freezing rain/drizzle.
Obviously it is still early and I will know more about the situation tomorrow and Friday.
A warm first half of summer for a majority of Canada.
Fast, west-to-east jet stream pattern across southern Canada into next week.
Clues to the long range over the next several weeks across North America.
Potential for significant rainfall over southwestern Alberta late this week into the early weekend.
A strong, upper-level storm system will bring significant rain, severe thunderstorms and much cooler air to parts of western and central Canada into early next week.
Latest ideas on the weekly long range through the end of this month.