Why Kamloops is sunnier than the Okanagan | iNFOnews | Thompson-Okanagan's News Source

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Why Kamloops is sunnier than the Okanagan

People living in the Okanagan Valley are very familiar with those dark gloomy days where low cloud blocks out the sun for weeks at a time.

It's caused by temperature inversions the Okanagan winters are famous for. It's not a unique or specifically local Okanagan phenomenon but often blankets all of the Southern Interior at the same time.

It’s just that different valleys – like the Thompson River Valley through Kamloops – react to them differently.

“It can really be a widespread issue right across the Interior of B.C.,” Environment Canada meteorologist Alyssa Charbonneau told iNFOnews.ca. “Things that cause an inversion for Kelowna cause an inversion for many other places in the Interior of B.C. as well. It definitely is not just one location that sees these happen. They set up everywhere.”

Normally, air cools off at higher elevations but, during an inversion, there is warmer air aloft, trapping cooler air in the valleys.

READ MORE: The under-appreciated weather phenomenon that makes for mild winters in Kamloops, Okanagan

That pattern can cover wide swaths of the Southern Interior at the same time, often leaving ski hills in bright sunshine while the valleys are socked in by layers of “valley cloud.”

There are a couple of key factors that make Kamloops and the Okanagan different even if they are impacted by the same weather system.

“Obviously there’s a lake (in the Okanagan) so, water vapor at the surface can increase the amount of strata (clouds) so you get that low deck of cloud and fog that can form in the bottom of an inversion,” Charbonneau said.

Usually, during inversions, there’s not a lot of wind. But Kamloops is twice as windy as Kelowna.

Environment Canada no longer tracks some weather data, including wind and hours of bright sunshine, but does have that data posted from 1981 to 2010.

It shows that winds in Kamloops average 10.3 km/h over the course of a year versus 5.4 km/h in Kelowna.

That means that the low lying clouds may get pushed out more easily in Kamloops.

The orientation of the valleys makes a difference as well.

Winds in Kamloops are generally northerly while they’re easterly in Kelowna. Penticton, which is actually a bit windier than Kamloops, gets a mix of north and south winds.

Wind and sunshine data are not available for Vernon.

Those winds clearing out the low lying clouds may be a major contributor to Kamloops having an average of 131 more hours of bright sunlight than Kelowna each year.

During that 1981-2010 time period, Kamloops averaged 2,079.8 hours of bright sunshine each year verses 1,948.9 in Kelowna.

Penticton had even less sunshine with 1,923.3 hours.

December is the gloomiest month of the year throughout the region with only 35 hours of bright sunshine in Kelowna. That increased to about 40 in January and 81 in February. Sunshine peaked at 298 hours in July.

That’s the same pattern for Kamloops but it got 47 hours of sunshine in December, increasing to 303 in July.

That increased sunshine also helps warm the cooler low lying air during and inversion, lessening its impact.

The good news is the current inversion impacting the Southern Interior is likely to end next week as unseasonably warm weather ends this weekend with slightly cooler temperatures to follow next week.

The bad news is that a number of weather systems will bring clouds and likely rain to the region, blowing out that low lying, cooler air.

“It's still cloudy, but it’s not as oppressive in that way,” Charbonneau said.

The downside is that, even the skiers won’t be able to escape the gloom as the mountains are likely to be clouded in as well.

To contact a reporter for this story, email Rob Munro or call 250-808-0143 or email the editor. You can also submit photos, videos or news tips to the newsroom and be entered to win a monthly prize draw.

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