Summer starts Friday but this part of Canada has thundersnow

Caroline FloydMeteorologist

The official start to summer is just days away, so why is British Columbia seeing thundersnow?

Driving in the mountains can be tricky at the best of times, but Mother Nature seemed to have a particular grudge against those traversing parts of the B.C. Interior on Wednesday. Not only were roads hampered by very late-season snowfall, but lightning and rumbles of thunder accompanied these bursts of snow.

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Environment Canada issued a special weather statement Wednesday morning for parts of the Coquihalla Highway and the Okanagan Connector cautioning travellers about accumulating snow above 1500 metres and a mix of rain and snow down to 1100 metres as freezing levels dip very low for late June.

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The Okanagan Connector near Aspen Grove on Wednesday morning. Image courtesy DriveBC.

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The culprit is an unusually strong (at least, for this time of year) upper-level disturbance that's swinging down into the coast, bringing with it a blast of cold air from the Gulf of Alaska. This dose of colder air has made for a very unstable atmosphere over southern B.C. It's the same setup that's driving severe weather in the western Prairies, but when combined with the Interior's higher elevations producing thunderstorms with intense snow showers rather than drenching rains.

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Hwy 97C at the Pennask Summit. Image courtesy DriveBC.

This disturbance is forecast to continue moving south slowly through the rest of the week, but its eastward progress is being blocked by high pressure over the Prairies, and that means it will remain a weather-maker for the province this week.

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Showers and thunderstorms are likely for even as far west as Vancouver Island through Wednesday, while much of the rest of the action for the rest of the week focuses on the Interior.

Showers, thunderstorm, and high-elevation snow are all in the cards through the end of the week, particularly for the southeast, with the bulk of the snow threat lying over the higher terrain of the Rockies (and, fortunately, away from travellers).

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