Slightly below normal temperatures through the holiday weekend. Scattered showers and isolated thunderstorms over the Sierra, northern Sacramento Valley and surrounding mountains into the early evening. Dry and breezy conditions return early next week with a warm up through mid-week.
Discussion
Leading short wave with trough approaching the West Coast has brought a few sprinkles and light showers to NorCal overnight. Most locations have reported just a trace, but a few foothill and mountain locations have gotten a few hundredths.
Main upper low will swing through the Pacific Northwest this afternoon with trough extending south over NorCal. This will continue the cooler conditions and breezy onshore winds. As the the system moves through expect scattered showers over Shasta county, spreading south over the northern Sierra into the afternoon.
Isolated thunderstorms will also be possible over Shasta county, the southern Cascades and northern Sierra this afternoon and evening. Instability appears to be on the low side at this time, so not expecting widespread thunderstorm activity, but possibly some isolated small hail. Best chances as highlighted by HREF and CAMS will be over eastern Shasta and Tehama counties, including Lassen Park.
Rainfall amounts are expected to be light with little in the Valley and less than 0.25 inches over the mountains. Although, there could be some locally heavier amounts in stronger storms. Snow levels will remain above 8,000 feet, so not expecting any snow at pass level or below.
Ensembles and clusters show the upper low moving into the Great Basin Monday, as this occurs onshore gradients will reverse and become offshore. The EFI is highlighting portions of northern California for elevated north winds Monday and Tuesday with gusts up to 30 mph.
Strongest winds are expected over the Northern/Central and Western Sacramento Valley. This will likely bring elevated fire weather concerns back to the area Monday and Tuesday. Valley temperatures warm back into the 90s by Tuesday next week.
Extended Discussion (Wednesday through Saturday)
Dry and warm Wednesday as upper ridge moves through. Several short waves progged into NorCal Thursday into Saturday bringing a threat of showers to mainly the mountains of Shasta county. Cooling trend expected through the extended with highs around 10 to 15 degrees above normal Wednesday, lowering to near to slightly below normal by Saturday.