As a strong storm system rolls out of the southern Canadian Rockies and onto the Prairies, there will be an elevated risk of tornadoes over southeastern Alberta and southern Saskatchewan on Thursday.
The storms will threaten lives and property, including agriculture in the region. Lowering snow levels and gusty winds will also reach from the Pacific Northwest in the United States and southern British Columbia to the foothills and Prairies of Alberta. Heavy rain will raise the risk of flash flooding.
According to Canada Weather Expert Brett Anderson, "An unusually strong storm system will roll across the area and will tap into humid air streaming into the region."
The area of greatest concern for tornadoes will reach along the Trans-Canada Highway (Highway 1) from Medicine Hat, Alberta, to Moose Jaw, Saskatchewan, and as far north and east as Saskatoon and Regina, Saskatchewan. Violent storms capable of producing tornadoes may also rip across northern Montana, along part of US Route 2.
"Strong winds, shifting direction above the ground could fuel tornadoes over the southern Canada Prairies that could be powerful and long-lived," Anderson said.
Large hail and frequent lightning strikes will also occur in some of the storms.
The most likely time for the violent thunderstorms is from the late afternoon into the evening hours on Thursday.
According to Severe Weather Expert Henry Margusity, "Just as April and May is tornado season over the United States, June and July is tornado season over the Canada Prairies."
This as the jet stream shifts northward from the spring to the summer. The jet stream is a strong river of air high above the ground that guides storm systems along and can give thunderstorms extra severity.
Winds associated with the potent storm will gust to over 80 kph (50 mph) and will be accompanied by heavy rain and even some snow.
"From 25 to 75 millimeters (1 to 3 inches) of rain will fall across portions of southern British Columbia, including the Canada Rockies, which could be enough to trigger flash flooding," Anderson said.
"The rainfall could be good news for firefighting efforts in the region, however."
The storm system will produce lowering snow levels over the northern Cascades in the United States and across the mountains of southern British Columbia and southwestern Alberta.
For example, according to AccuWeather Senior Meteorologist John Greskiak, "Snow levels will lower to 7,000 feet on Wednesday and as low as 5,000 feet Wednesday night."
The sudden snow, high winds and thunderstorms can catch hikers and other outdoor interests off guard, Margusity added.
Windswept rain and plunging temperatures will affect the major Alberta cities of Calgary and Edmonton on Thursday and Thursday night.
"Strong crosswinds from the north and northwest could pose problems for high profile vehicles such as RVs and trucks along the Trans-Canada Highway and other heavily traveled roads in the region," Anderson said.
The same storm system will continue to drift eastward along the Canada/US border into the end of the week.
There is a chance of strong to locally severe thunderstorms in southern Manitoba and North Dakota to northwestern Minnesota on Friday.