Big Heat, Fire Weather Concerns by Weekend

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Northern California’s unusual summer will be ending with yet another big dose of heat, possibly record setting once again, and this along with plunging humidity levels will create renewed fire weather concerns during the upcoming Labor Day weekend.

The Wednesday satellite view showed fires in the Mendocino National Forest still putting out lots of smoke, and an extensive fog/marine later pushing into the North Bay.

That marine layer will be pushed to the coast and less extensive by week’s end, as another giant ridge of high pressure arrives to dominate California weather.

Already Excessive Heat Watches and Warnings are up for almost all of the state from Saturday through Tuesday as the unusually strong high pressure system pushes in, this time from the Pacific Northwest.

By Saturday, high pressure will reach maximum strength over California and is expected to stay here for several days.

This will bring subsiding air, compressing our cooling marine layer, and ushering in record, or near record heat. In fact, by Sunday and Monday, expect temperatures 15 degrees or more above normal. Yes, those are potential temperatures over 110 degress in the Central Valley.

A closer look at the GFS model forecast shows temperatures possibly reaching 105-110 degrees in the hot spots of Sonoma, Napa and Lake counties on Sunday and Monday.

And, humidity levels will plunge as well, with relative humidity in the teens across the region. With hot weather in place, this will lead to renewed fire weather concerns.

Finally, smoke will remain an issue. With air becoming stagnant under the huge high pressure system, air quality concerns will once again rise as regional fires continue to burn and smolder. This forecast shows smoke continuing to be an issue in North Bay valleys.