An out-of-season storm will send colder air, gusty winds, high country snow and locally severe thunderstorms across the northwestern United States and western Canada this weekend to early next week.
The storm will spin ashore from the Gulf of Alaska this weekend. As it does, a wave of colder air will be forced inland and southward. The leading edge of this air will raise the risk of severe thunderstorms from the northern Rockies of the U.S. to the southern Rockies in Canada, as well as part of the Canada Prairies.
There is the likelihood for some road closures and sporadic power outages as well as a risk to lives and property.
While this storm is not nearly as intense as some storms during the winter it has the potential to catch outdoor interests by surprise over the mountains with a rapid change to colder and snowy conditions. Hikers not prepared for the rapidly changing weather conditions may be at risk for getting lost and developing to hypothermia.
Snow may dip to the pass levels of the Cascades and Rockies and the peaks of the Olympics and Coast Mountains in the region. While an accumulation on the roads over the passes is not likely, motorists are likely to face sudden, strong wind gusts and poor visibility.
Temperatures will be trimmed by 10-15 degrees Fahrenheit (5-8 degrees Celsius) at sea level along the coast.
Meanwhile, a more significant temperature plunge of 20-40 F (10-20 C) is projected over the interior with the greatest crash over the mountains. AccuWeather RealFeel® Temperatures will dip to 10-20 F (5-10 C) lower than the actual temperature.
Some cooler air will reach as far to the south as the northern parts of California, Nevada and Utah and surge as far to the east as Wyoming, Montana, Alberta and Saskatchewan this weekend.
Eventually, the cooler air will reach the Dakotas and Manitoba early next week.
Severe weather outbreak may unfold in Canada, northern tier of US
The risk of severe thunderstorms will increase this weekend.
"The stage is set for a severe weather outbreak over parts of Montana and Alberta on Saturday and the Dakotas and Saskatchewan to part of Manitoba on Sunday," according to AccuWeather Canada Weather Expert Brett Anderson.
"The strongest storms will be capable of producing damaging wind gusts and large hail," Anderson said. "There is also the potential for tornadoes."
The highest risk for violent storms may be across south-central and southeastern Saskatchewan, northeastern Montana and northwestern North Dakota during later Sunday afternoon then southwestern Manitoba Sunday evening.
Motorists and people living in or spending time in the advised area this weekend should be on the lookout for rapidly changing weather conditions.
Seek shelter indoors as storms approach and avoid parking under large trees. If out in the open, low-lying ditches may offer some protection from high winds and a tornado.
Never attempt to drive through a flooded roadway. If travelling on the highway, pull well off the road to a sheltered location until the storm passes.
On a positive note, much of this region is still experiencing long-term drought conditions, so any significant, non-flooding rainfall will be beneficial.