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December 12, 2018 – A weak weather system brushes far northern California early today, otherwise dry weather will continue until the end of the week when a more active storm pattern returns.

Discussion

Short-wave exiting to the east through northern Nevada early this morning. Showers overnight brought less than a tenth of an inch of precipitation to the far northern portion of the forecast area while the remainder of interior NorCal is seeing varying amounts of cloud cover. Current temperatures are considerably milder across most of the area compared to 24 hours ago and range from the 30s in the mountains to the 40s elsewhere.

Subsidence and drying northerly flow develops by midday ridging at the surface and aloft increases resulting in clearing skies. North winds will also increase becoming locally breezy through portions of the Sacramento Valley.

Dry weather pattern continues on Thursday, then Pacific frontal band forecast to move gradually into/through NorCal Friday and Friday night, weakening as it does. Appears most of the QPF will remain to the north of I-80 with around a third to half an inch over the Coast Range, around a third of an inch across the northern Sacramento Valley and around half an inch over the northern mountains. Snow levels around 5-6k feet will have some minor travel impacts over the higher passes.

Some showers linger across the region Saturday before the next system approaches Saturday night.

Extended Discussion (Sunday through Wednesday)

Moderately strong Pacific frontal band still on track to move into NorCal on Sunday. Main impact on Sunday will be to the coast range where the heaviest precipitation is expected initially. Timing still varies a bit across models but should start seeing more significant snowfall over the Sierra passes Sunday evening and overnight into Monday. With snow levels below pass levels and several inches of snowfall projected, travel impacts over the Sierra are likely Sunday night into Monday.

Brief upper ridging will bring an end to precip over the southern CWA Monday night but could see some light precipitation riding over the top of the ridge for some light rain north of about KMYV. Central valley areas south of KMYV could see some fog return but cloud cover should keep it to a minimum. Upper ridging keeps precipitation limited to the northern CWA on Tuesday with ridge building enough by Wednesday to keep precipitation mainly north of the forecast area. Daytime temperatures should come in around normal Sunday through Tuesday under mainly cloud covered skies but clearing the middle of next week will allow daytime highs to climb to a few to several degrees above normal.