Fall officially begins Friday night, and Northern California will certainly feel the changing of the seasons this week. A mix of weather conditions is in store from the Bay Area to the Sierra Nevada. The Bay Area will see partly cloudy skies with seasonal temperatures through Wednesday, but changes are coming for the second half of the week. By Thursday, north winds are expected to clear out skies and elevate the fire risk in the Sacramento Valley. However, these winds will bring chilly air to the mountains, possibly cool enough for the first snowflakes of the season in the high Sierra.

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• Marin Independent Journal: Bay Area weather forecasts - El Niño conditions through winter