September 2, 2016 – Mainly dry weather for NorCal with slightly below average temperatures through early next week. A slight chance of showers southern Cascades and foothills Saturday night. Warming expected the second half of next week. Locally breezy at times, mainly in the Delta and over ridgetops.
Upper trough over the west coast will continue to bring cooler than normal temperatures to northern California over the next several days. Currently, flow around this trough is dragging cloudiness from a low over the Aleutian islands into the far north state. At this time, models keep precipitation north of the state today.
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A shortwave digging into the Pacific Northwest on Saturday will bring a little more cooling bringing daytime highs down a few to several degrees below normal. This disturbance clips northeast California Saturday night. Models have been fairly consistent now for the last several runs in bringing light precipitation to the northeast corner of the state. This threat of light precipitation will continue through Sunday morning. By Sunday afternoon the upper trough axis shifts east of the state. This should end the shower threat as upper flow becomes northwest. Overall airmass cools just a bit more Sunday making it the coolest day of this stretch of cooler than normal weather. Upper ridging begins to build in on Monday bringing a slight warm up but highs will still remain slightly below normal.
Extended discussion (Tuesday through Friday)
An upper level trough will begin to move to the east for the start of the long term forecast period on Tuesday as a ridge of high pressure builds in the eastern Pacific. As a result, temperatures will warm back up to near or slightly above normal for the rest of next week. The strengthening high pressure system will keep stable conditions over NorCal and will make precipitation unlikely.