Moisture from Eugene will be working into NorCal creating isolated mainly mountain showers and thunderstorms starting today through early next week. Temperatures will slowly warm over the weekend and into next week.
Cool start to the day with some cloud cover will keep temperatures lower today especially over the southern half of the forecast area. Some sprinkles this morning over parts of the San Joaquin valley will likely dissipate this morning.
Today chances for thunderstorms develop along the crest mainly south of US-50 in the afternoon. Models are still suggesting a decent amount of rain forecast near the crest south of highway 50, so any lightning starts would likely be hard to spread.
Easterly flow will continue to bring moisture westward today towards the San Joaquin valley where some isolated light showers or sprinkles may occur. Any rainfall will be limited for the lower elevations mainly below about 5000 feet and the atmosphere should become more stable for the nighttime hours helping to limit any thunderstorm activity.
Similar pattern sets up for Saturday and Sunday with an abundant amount of moisture and clouds over the area. Chances for precipitation will be moving further northward along the crest during the afternoon and evening hours up to the Southern Cascades. Easterly flow will continue to try to move some activity towards the foothills each afternoon and evening.
Some instability is indicated over the Central and Northern Sacramento valley Saturday through Monday but at this time models continue to keep the valley dry but sprinkles at times are a possibility. This is something we will continue to keep a watch on given the uncertainty in predicting monsoonal moisture and its impacts but Sunday and Monday looks to be the more unstable days for the valley. The low does stay well south of the area so that helps to keep the greatest instability over the mountains due to the natural orographic uplift.
Extended Discussion (Tuesday through Friday)
Closed upper low off the SoCal coast Tuesday modeled to gradually drift NW and slowly deepen through the week. System will draw moisture and instability into the CWA Tuesday and Wednesday with a threat of afternoon showers and thunderstorms over the mountains.