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November 30, 2018 – Light showers over the Sierra today. Significant Sierra snow and lower snow levels Friday night and Saturday creating significant travel impacts. Dry Sunday and Monday. Next chance of precipitation next Tuesday.
Upper low that brought rain, snow and thunderstorms on Thursday has now moved into the Great Basin with just a few showers over the Northern Sierra at this time. A chance of a few showers will continue today over the Sierra Cascade range within the cyclonic flow of the upper low but significant snowfall is not expected.
Next Pacific frontal band poised to move into northern California over night tonight bringing rain and mountain snow. Heaviest mountain snow will over over the Sierra where orographics will enhance snow amounts.
A foot or more of snow will will be possible at the higher elevations with snow levels dropping to below 4000 feet. Combination of relatively low snow levels, breezy west winds and snowfall will make for hazardous travel through the Sierra Cascade range tonight.
This system will not be as strong as the Thursday system with valley rain amounts remaining fairly light. Main cold frontal band forecast to move quickly through NorCal on Saturday with the main upper low pushing through NorCal Saturday night.
Clearing skies and cool airmass will make for cool morning lows on Sunday. Northerly winds behind the front will bring drying with shower threat ending all areas by mid day Sunday. Sunday should turn out to be a fairly nice day under clearing skies with daytime temperatures warming a little although still several degrees below normal for this time of year.
Fair skies and cool airmass will make for a chilly night Sunday with morning lows on Monday predicted to drop below freezing most central valley locations. Upper ridge will keep forecast area dry on Monday but increasing clouds will be seen in the afternoon as the next Pacific storm system approaches the coast. Light pre-frontal precipitation could start to fall over interior northern California as early as Monday night or Tuesday morning.
Extended Discussion (Tuesday through Friday)
The wet pattern is expected to continue next week. A strong closed low slides southeast over the eastern Pacific, approaching California Tuesday through Wednesday. Models confidence is still fairly low on the exact path of the low. Current model runs show the lee side of the trough clipping NorCal as it slides south off the coast before coming onshore south of our forecast area Friday. If this holds, this storm system will not be a high impact system. Generally, liquid precipitation amounts through Thursday are under an inch across NorCal, except the Coastal Range could see up to 2 inches. Models bring in another brief weather system next Saturday. Keep an eye on the forecast as details for these systems change.