Below normal high temperatures will persist early this week with periods of breezy conditions. Temperatures will warm to above normal levels by Thursday or Friday. Smoke and haze from wildfires will continue to impact portions of interior Northern California.
Discussion
Infrared GOES-West imagery shows the hotspots of the numerous active fires burning across the state, including the Caldor, Dixie, McFarland, Monument, and others. Marine layer along the coast is about 2,000 ft deep with a decent Delta breezy blowing; Travis Air Force Base is presently gusting between 25 and 30 kts. Clear skies with the lack of smoke over the Valley will allow for efficient radiational cooling, allowing temperatures by sunrise to fall to the 50s to 60s for Valley communities.
Weak troughing just west of the coast will promote west/southwest flow aloft over the next few days with onshore flow at the surface. Locally breezy south to west winds will be likely in the wind-favored locations for this type of synoptic setup on both Monday and Tuesday afternoons/evenings, including the Delta, portions of the Sacramento Valley, as well as higher elevations of the Sierra Nevada. Continued onshore flow will help keep afternoon highs generally at or slightly below late August climatological normals through Wednesday. Best guess National Blend of Models seems to be a bit bearish for temps the next few days, especially given the likelihood that skies over the Valley will significantly less smoky compared to last week. Thus, have nudged toward the 75th percentile.
West Coast trough will push inland on Thursday with the upper level flow becoming more northwesterly for the second half of the week. 500 mb heights will climb as an upper level ridge over the Pacific at around 40N / 140W builds broadens and builds east towards North America. This will result in likely day-to-day warming across NorCal with temperatures at or above normal for Thursday and Friday. Will have to keep an eye for possibly northerly/easterly winds around Thursday with this trough axis passage.
Extended Discussion (Friday through Monday)
Several short wave troughs move through the PacNW during the extended forecast period as EPAC high remains offshore. Dry weather will result with above normal high temperatures. Max temperatures expected in the upper 90s in the Central Valley with triple digit heat in the Northern Sacramento Valley. Locally breezy north to east wind possible over the weekend with a potential for increased wildfire smoke over interior NorCal.