The recent wildfires in the Okanagan Valley was the culprit for the smoke and haze yesterday, but parts of the valley has since cleared out today.

Photo credit: KelownaNowThursday’s view of Kelowna
 

Photo credit: KelownaNowFriday's view of Kelowna

The fires are still burning, so WHY the big difference? It has a lot of do with what the weather pattern is doing at the upper levels.

On the 500 millibar chart, we have an upper low that moved into our region today. This chart represents what is happening at 5000 metres above the surface. We have circled the upper low in red. This is a meteorological term to describe an area of cooler air aloft.

In comparison, we had warmer air aloft over region yesterday under a weak upper ridge. We’ve circled the ridge in red on this chart. The upper low was still over the North Coast of BC on Thursday.

Because cool air is denser than warm air, when we have cooler air aloft, the cooler air sinks down to the surface. This movement of the cooler air displaces the warmer air at the surface and helps to mix the air vertically. The increase in vertical air movement encourages the smoke to move out of the valley.

There are also cold fronts associated with upper lows, and these fronts create wind during heir passage over our region. Strong enough winds can help the smoke dissipate.

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Photo credit: KelownaNowFriday's view of Kelowna looking southwest towards the fires.