June 4, 2021 – Above normal temperatures with dry conditions will continue through the week. Cooling trend will begin this weekend with near normal temperatures returning around Monday.
Discussion
Mostly clear skies overhead tonight with GOES-West infrared picking up just a few high clouds in far northwest Shasta County. Bit of a Delta breeze overnight with Travis Air Force Base gusting over 25 kt as of midnight PDT, though, not nearly as strong as 24 hours ago when they were gusting near 40 kt. As a result, temperatures from the Delta through the Sacramento metro area are running a solid 6 to 12 deg F warmer compared to this time yesterday morning. By sunrise, Valley temps will range from the upper 50s in Solano County to the upper 60s/low 70s in the northern Sacramento Valley.
Upper level ridge in the Great Basin will slowly shift eastward over the next 24 to 48 hours, allowing the anticyclonic flow that has prevailed over the last several days to transition to more zonal flow aloft.
This will result in some minor day-to-day cooling through Saturday. On Sunday, an upper level trough will approach the Pacific Northwest, and provide northern California with more noticeable cooling.
This trend will continue into Monday with high temperatures within a few degrees of early June normals (middle/upper 80s in the Valley).
Extended discussion (Tuesday through Friday)
Ensemble and cluster analyses indicate the Pacific Northwest trough will stick around through at least the middle of next week, and promote near or even below normal temperatures for the region.
Forecast confidence rapidly decreases toward the end of next week as clusters begin to advertise varying synoptic solutions.