100s Through Friday, Turning Cool and Wet by Monday

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High pressure pushing into the region has caused North Bay temperatures to soar. As of Thursday afternoon many inland locations like Santa Rosa, Healdsburg and Petaluma were near 100 degrees, and Friday is shaping up to be even a bit hotter.

The sudden heat has prompted the National Weather Service to issue a Heat Advisory for much of the Bay Area including most inland areas of the North Bay through Friday.

As hot as it will be Thursday and Friday, there are big changes on the way for the first part of the coming week. After a slight cool down into the 80s for the weekend, Monday and Tuesday will see the arrival of the deepest, coolest low pressure trough of the season.

In fact, the first high clouds and cool air will arrive on Sunday afternoon. By Monday, it will seem downright cold by comparison with our current weather. A genuine early blast of fall.

Here is the setup for Thursday and Friday…high pressure in control.

But, by late Sunday into Monday, low pressure swoops down from the north, bringing with it plenty of cool air and clouds.

The low pressure trough that’s headed our way will be driven by an unusually strong southward dip of the jet stream.

This will drive cool air into California, with highs across the North Bay mostly in the 60s for Monday, with a slow warming as the week progresses.

There will also be showers headed our way. While most of the rain will stay north (up to 1 inch near the Oregon border), we may get a few showers as far south as Sonoma County, with about a quarter of an inch possible as far south as Ukiah on Monday and Tuesday.

So get ready for big time heat, followed by some of the coolest, cloudiest weather we’ve seen since last spring. And, perhaps, even a few showers to wet things down a bit and reduce the fire danger as we head towards fall.