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February 25, 2018 – Below normal temperatures will continue. Additional systems this week will bring more widespread precipitation. The first system, with very low snow levels, will move into the region tonight and Monday. Winter Weather Advisory from 9 PM this evening to 2 PM PST Monday.

Discussion

Clear skies and milder temperatures (but still cold) across the region early this morning. Current readings range from the single digits to teens in the mountain valleys to the 30s and lower 40s in the Central Valley.

Next system is dropping southward off the BC coast and will spread precipitation back into NorCal tonight into Monday. The track is a little further to the west than last week’s system, so it will have a little more moisture to work with. Snow levels remain low, and will lower further tonight, so accumulating snowfall is likely once again down into the foothill elevations.

A period of heavy snow is expected across the northern Sierra late tonight and Monday morning as the cold front sweeps south, then snow showers will continue over the Sierra into Monday evening. Most of the QPF in the valley will occur as front moves through with amounts expected to generally be around 1/4 inch.

Subsidence and north winds will bring drying to the region Monday night into early Wednesday before the next system brings a return of precipitation by Wednesday night.

Extended discussion (Thursday through Sunday)

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Active pattern expected during the extended period as a trough deepens along the West Coast. Significant precipitation event possible beginning Wednesday night with strong frontal system and a deep moisture tap as depicted by the US West Coast AR Landfall Tool. Although timing differences are still evident, the storm system will bring precipitation across the northern mountains Wednesday afternoon and then spread precipitation inland Thursday into the weekend. Liquid precipitation amounts of 0.5 to 2 inches in the valley and 1.5 to 4.5 inches in the foothills and mountains are expected.

Snow levels are anticipated to be around 3500-4500 feet initially, then will drop to around 1500-2500 feet as cold air filters in. Substantial Sierra snow is expected, with the potential for several feet. In addition, tight pressure gradients will result in strong winds as the system moves through, especially over the Sierra. Therefore, strong winds combined with periods of heavy snow could lead to travel difficulties over the Sierra. Details are still changing with this weather system this far out, so stay tuned to future updates on this storm. Other than lingering activity over the mountains, latest guidance suggests drying conditions on Sunday.