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Mountain snow and Valley rain showers return late tonight through Tuesday along with strong winds. Another chance for wet weather possible late in the week.
A closed low over the Gulf of Alaska will slowly open and pivot onshore over the Pacific Northwest through Tuesday with its strong associated frontal system passing through NorCal. This system will be accompanied by modest Pacific jet energy and mid- level confluent flow to drive moisture into the region, with IVT approaching 750 kg/m/s over extreme Northern California. Snow levels through the period will remain low over Shasta county, generally 1500-3500 ft where heavy wet snow will develop early this morning. Onset of the snow has been delayed by about 6 hours versus previous model runs.
Plan on difficult travel conditions, including during the evening commute. Damage to trees and power lines is possible. Wet snow accumulations of 5 to 10 inches, above 1500 to 2000 feet, with localized amounts up to 2 feet above 3000 feet, are expected over Shasta county including Interstate 5. Higher snow levels expected over the Sierra to around 4000 ft where snow is expected to develop later today.
Have upgraded previous winter wx adv to winter storm warning due to the threat of high winds and very visibility in the the heavy snow over Western Plumas county. Downed trees and power lines are possible due to heavy snow and strong winds.
Wind gusts from 55 to 65 mph are possible with visibility near zero at times in heavy snow and strong winds. Total snow accumulations of 6 to 12 inches, with localized amounts up to 2 feet, are expected mainly over Plumas county and near Lassen Park. Lighter snow amounts are expected farther south down the Sierra where a winter wx adv is in effect including Interstate 80 and Highway 50 tonight into Tuesday for total snow accumulations of 3 to 10 inches, with localized amounts up to 15 inches.
Southerly winds will increase today across the Northern Sacramento Valley-Central Sacramento Valley. South winds 20 to 30 mph with gusts of 35 to 45 mph. Local gusts near 50 mph possible. Winds will begin to subside late Monday night or early Tuesday morning. These winds could blow around unsecured objects. Tree limbs could be blown down and a few power outages may result.
Ensembles indicate the precip and winds should diminish Tuesday afternoon with only a few light snow showers over the mountains. Valley precip will be fairly light with this system with amounts generally less than 0.25 inches. A bit more over the foothills from 0.50-1.00 inches.
Extended Discussion (Friday through Monday)
Pacific frontal system modeled to move through interior NorCal Friday bringing breezy to windy conditions with widespread light to moderate rain in the lower elevations and snow in the mountains. Snow levels look to be around 5000 to 6000 feet. Deterministic models differ next weekend into Monday, but ensembles support a drier solution with upper ridging moving through.