Hot streak will continue for the week with widespread triple digit high temperatures in the Valley. Monsoon moisture heading north will set off showers and isolated thunderstorms through Thursday with the best chances over the Sierra north into the Shasta County mountains and the Coastal range late tonight and Wednesday.
Upper level high pressure remains the dominant weather feature over CA keeping the prolonged hot temperatures through the work week. Also, monsoon moisture is spreading north and will bring mountain showers and thunderstorms to the Sierra today through Thursday, and along the Coastal range late tonight and Wednesday.
This moisture will also bring a layer of clouds to Northern CA late tonight and early Wednesday morning that will keep minimum temperatures quite mild in the Northern San Joaquin through Central Sacramento valleys tonight.
There is some mid level instability so some virga or a stray lightning strike/thunder in the Sacramento valley is possible Wednesday morning. Also, folks in the Northern Sacramento Valley will also see a return to smoke and haze from the nearby 6 Rivers Fire.
By late Thursday, the monsoon moisture will push off to the east, removing the thunderstorm threat across northern California. At that same time, a weak system will move across Northern California that will bring a return to onshore flow and the Delta Breeze, slightly decreasing temperatures. Not expecting a huge Delta breeze so it will be limited cooling, mainly to portions of the Sacramento Valley adjacent to the Delta.
Even with the added relief of the Delta breeze, abnormally warm temperatures will remain through the work week, especially across the northern Sacramento Valley. Therefore, a heat advisory remains in effect through Friday evening to account for the hot conditions.
Extended Discussion (Saturday through Tuesday)
Upper ridging over NorCal progresses eastward over the weekend as upper trough approaches the Pacific Northwest Monday. This troughing will bring some relief Sunday and Monday with temperatures near normal. Ridging then rebuilds Tuesday, and temperatures trend up again Tuesday. Dry weather expected through the extended period.