August 14, 2017 – Cooler early this week, then warming back to near or slightly above average around mid-week.
Lots of high clouds moving over interior NorCal early this morning as the upper trough moves onto the West Coast. Onshore gradients have increased and a robust Delta Breeze is bringing gusty southerly winds thru much of the Sacramento Valley. Current temperatures are milder compared to 24 hours ago in the mountain valleys where the increase in clouds and wind are holding temps mainly in the 50s and 60s. Elsewhere, current readings are pretty similar to yesterday.
The trough will continue to deepen over the region into early Tuesday resulting in the coolest weather in over a month early this week. The best chance for any showers or thunderstorms will be this afternoon across northeast California as the front slides south (perhaps the Mt Lassen area may see some activity). Otherwise, the main effect will be cooling and locally breezy conditions into Tuesday.
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Ridging from the eastern Pacific begins to reassert itself by mid-week and will result in temperatures returning to around average or slightly above beginning Wednesday.
Extended discussion (Friday through Monday)
Ridging begins to break down on Friday as upper level troughing moves onshore for the weekend into early next week. As troughing returns and a bit of moisture is drawn north, isolated thunderstorms will be possible Friday and Saturday afternoons near the Sierra crest south of Tahoe. Temperatures will cool slightly from Friday to Sunday with afternoon highs back within a few degrees of normal.