Moderate heat risk will continue for parts of the interior through this week. Breezy to windy conditions continue in the Delta each day. Slight chance for thunderstorms late Monday night though Tuesday.
High Sierra monsoonal thunderstorms chances are forecast each day near crest into the weekend.
Similar weather conditions are forecast today with highs trending lower by a degree or two. Moderate heat risk continues for the northern Sacramento Valley with low risk for areas influenced by the cooling effect of the Delta. Smoke from the Oak Fire has overspread the Sierra as indicated by satellite imagery as well as air quality monitors across northern California. The latest HRRR smoke forecast shows areas in the Motherlode and Sierra will likely see smoky conditions continue once again today with some clearing near the surface in the afternoon for the lower foothills.
The Delta breeze will help to bring in fresh air from the Bay into the Valley however, elevated smoke will be likely leading to hazy skies over the region. Ensembles and high resolution model guidance are in agreement a small low pressure currently off the central coast of California will make its way northward along the coast early this week. This feature will bring southerly flow through the Valley and increase mid to high level moisture over the region.
By late today shower chances increase over the Sierra and potentially spread northwest over the Valley and into the Coastal Range. NAM model soundings show potential for a few isolated elevated thunderstorms to form in the early morning hours on Tuesday from the northern San Joaquin Valley to points northward in the southern Sacramento Valley and Delta. Very dry air in the lower levels will limit the potential for precipitation associated with any storms that may form.
Shower chances slowly shift northward through the day and decrease in the Sacramento region as the impulse continues to spread northward into the early evening. Virga and mid to high clouds over northern California are anticipated as well as overall synoptic cooling by a few degrees.
Overall chances remain low in the Valley with orographic lift boosting the potential for storms to develop over the higher elevations including the Sierra. The EFI is also continuing to highlight onshore winds through the Delta each day. This continued onshore flow will help to limit heat risk in the southern Sacramento Valley and northern San Joaquin Valley.
The EFI is also highlighting warm max temperatures over far northern California, generally north of Redding. Highs in the northern Sacramento Valley will likely continue to be over 100 degrees throughout the week with moderate heat risk continuing.
By Thursday, high pressure building over the West will lead to a warming trend with areas of high heat risk expected for portions of Shasta County.
Extended Discussion (Friday through Monday)
Similar day to day weather conditions continue into the weekend. Ensembles are in agreement high pressure will be centered over the Western US, extending into the Pacific northwest. Monsoonal storms will be possible along the crest mainly south of Tahoe. Temperatures will also continue to be seasonably warm for this time of year.