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January 13, 2020 – Several systems will move through the area early this week. A second system will move through Monday night and Tuesday morning. The third system will move through late Wednesday through Thursday. Each system will be stronger than the prior one with snow levels lowering into the foothills for the second and third systems and possibly into the north end of the valley by Thursday.

Discussion

Radar shows some light showers across the northern Sierra and foothills early this morning as a weak system moves through the area. The remainder of the area is under clear to partly cloudy skies with some areas of stratus over the Sacramento Valley. Current temperatures are mostly milder compared to 24 hours ago and range from the upper 20s and 30s in the mountains to mainly 40s across the Central Valley.

Persistent northwest flow will send another system our way tonight into Tuesday. This one is forecast to be a little stronger and track a little further south than the current weak system. QPF will be focused mainly over the foothills and mountains where 1/4 to 3/4’s of an inch is expected with local amounts above an inch. The valley will likely only see a few hundredths of an inch. Snow levels will generally range from 1500-2500 feet across the northern mountains, and 3000-4000 feet elsewhere with up to a foot of snowfall accumulation possible over the higher elevations.

Much of the area may see a break in precipitation Tuesday night into early Wednesday ahead of the stronger system Wednesday night and Thursday. This system will be the most impactful of the past several weeks for NorCal with moderate to heavy precipitation, heavy mountain snow and gusty winds expected. QPF of 1/2 to 1 1/2 inches is forecast for the valley with 2 to 3 inches over the foothills and mountains. Several feet of snowfall accumulation will be possible over the upper foothill and mountain elevations. Post-frontal thunderstorms will also be possible Thursday.

Extended Discussion (Friday through Monday)

Some light overrunning precip possible on Friday, mainly over northern portions of the CWA, otherwise drier weather expected as short wave ridging moves through. Models showing another Pacific frontal system moving inland beginning early Saturday. The front weakens as it moves into the CWA Saturday with the bulk of precip being north of I-80. Drier weather returns Sunday into Monday as upper level ridging moves over NorCal.