August 3, 2016 – Mainly dry weather with seasonal temperatures this week. Isolated mountain thunderstorms possible Friday and Saturday over the Coastal Range.
Short term discussion (Today through Friday)
A shortwave ridge of high pressure has moved over Northern California, sandwiched in between upper lows off the coast and along the northern Rockies. As a result, onshore flow has generally been weaker than yesterday, and the marine layer along the coast has been squashed down to ~1200 ft (down from 2000 ft yesterday). With these factors in play, temperatures across the region are running warmer than 24 hours ago. This temperature trend will continue through the day, with afternoon highs expected to reach the upper 90s to around 105 degrees across the Valley, and 80s and 90s over the mountains.
The aforementioned offshore low will move toward California on Thursday, strengthening as it approaches. Additional shortwave troughs will rotate through the region Friday into Saturday. This will usher in a noticeable cooling trend across the region, with Valley highs dipping into the 80s to lower 90s. The atmosphere appears too dry and stable for convection on Thursday, but we could see some isolated thunderstorms Friday and Saturday along the Coastal Range. The best chance of thunderstorms will likely remain north of our forecast area.
Extended discussion (Sunday through Wednesday)
Cooler weather continues over the weekend as the parent upper level trough lingers over the Pac NW with high temperatures near to just below average and increased Delta and ridge winds. The most prominent shortwave swings through Tuesday, but any showers looks to remain north into Siskiyou County.