March 8, 2019 – Scattered snow showers this morning for mountain travel delays Northern Sierra. Light to moderate snowfall over the northern mountains Saturday for possible northern mountain travel impacts. Showers Sunday and dry Monday. Another fairly weak system passes through next Tuesday.
Weak upper trough passing over NorCal with trough axis near the NV/CA border at this time. Radar showing light showers over the northern Sierra this morning with Blue Canyon reporting light snow throughout the evening and early morning hours and chain controls still up on 80 and 50. Therefore, will leave winter weather advisory for Northern Sierra/Southern Cascades up through the morning hours. Should see decreasing showers this afternoon as upper trough axis shifts eastward.
Areas east of the Sierra foothills should remain dry today under a period of upper ridging. This break will be brief, however as a fairly weak Pacific frontal system now approaching 140 west approaches the coast. The northern half of the forecast area could see some light precipitation as early as this evening as a pre-frontal shortwave passes through the north state.
The main cold front will be moving through NorCal on Saturday. Entire CWA will see a threat of precipitation on Saturday but bulk will be north of about interstate 80. With snow levels expected to be as low as 1500 to 2500 feet and snow amounts of several inches possible, will issue a winter weather advisory for the northern mountains to cover possible weekend travel issues Saturday. Lighter amounts of mountain snow and valley rain are expected elsewhere and impacts should remain minor with this relatively low moisture system. Showers continue into Sunday as main upper trough drops across the region.
At this time, Monday looks dry under dry northerly flow but could see another round of light precipitation entering the northwest corner of the state as early as Monday night as a weak Gulf of Alaska system pushes onshore.
Extended Discussion (Tuesday through Friday)
Pacific frontal system drops into the area from the NW on Tuesday bringing light to moderate precipitation to Interior NorCal. Snow levels forecast to range from 2500 to 3500 feet. Drier weather returns Wednesday and continues into Friday under upper ridge. Breezy north to east wind develops Wednesday under building high pressure and persists into early Thursday. Warming trend through the extended period, but temperatures remain below normal.