September 16, 2016 – Dry through the extended period. Above normal temperatures through early next week. Temperatures then return to around normal for the rest of the week.
Upper level high pressure ridge remains over the west coast and will dominate the weather pattern over the next several days. Highs on Thursday came in several degrees up from the previous day and this trend has continued into this morning with temperatures up a few degrees most areas from 24 hours ago. Marine layer is still fairly patchy but may see a little stratus this morning in the western delta.
High temperatures will come up a few degrees more today as the upper ridge axis pushes inland. Clear skies overnight will allow overnight lows to drop down to near normal tonight.
Temperatures warm a bit more on Saturday putting daytime highs between 5 and 10 degrees above normal. Only minor changes are expected in temperatures Sunday as the upper ridge slides slowly into the western U.S. An upper low in the Gulf of Alaska is forecast to approach the Pacific Northwest coast on Monday flattening the western U.S ridge and bringing a slight cool off but daytime highs are still likely to come in a few to several degrees above normal.
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Extended discussion (Tuesday through Friday)
A weak trough will track across NorCal Tuesday into Thursday. The center of the associated low pressure system will be well north of our region over Washington state and the Canadian border. Thus the passage of this trough will have limited impacts as precipitation stays to the north. Our CWA will experience a cooling trend with temperatures near normal on Tuesday, then going slightly below normal Wednesday and Thursday. Winds could be a bit breezy over mountain ridgetops during the trough passage. Daytime highs return back to normal by Friday as the trough exits eastward.