Strong high pressure will continue hot weather this week, particularly for the northern half of the Sacramento Valley and surrounding terrain. Slight chance of late day thunderstorms returns to the Sierra beginning today.
Discussion
Strong subsidence continues to result in clear skies across interior NorCal. IR difference imagery shows extensive stratus along the coast extending well inland again early this morning, and a strong Delta Breeze continues to bring cooling into the Central Valley. Profiler data indicate the marine layer depth is around 1k ft. The surface thermal trough has migrated a bit further to the north and east allowing onshore gradient to extend further inland, and inland temperatures are a bit cooler compared to 24 hours ago.
The cut-off low that’s been off the coast over the weekend will begin to move north later today and Tuesday. NorCal will remain on the periphery of the strong high centered over the PacNW, though heights aloft are forecast to weaken slightly allowing some moisture to work its way back to the west beneath the high. Isolated late day thunderstorms will be possible later today in the Sierra south of Lake Tahoe, but further north will likely remain capped. Storms may develop a little further to the north on Tuesday thru Thursday, but most will be east of the Sierra/Cascade crest.
Hot weather will continue across inland areas this week, though likely not quite as hot as over the weekend. Enough Delta Breeze is expected to help keep temperatures moderated across the southern Sacramento and northern San Joaquin Valleys.
Extended discussion (Friday through Monday)
Interior Northern California remains sandwiched between upper trough offshore and Desert SW high during the extended forecast period. This will result in continued above normal daytime temperatures with triple digit heat persisting in the northern and central Sacramento Valley. Mid level southerly flow is favorable to draw increased moisture over the Sierra Nevada leading to a threat of afternoon showers or thunderstorms Friday through Sunday.