November 27, 2018 – Some patchy morning fog in the Central Valley, otherwise precipitation is expected to gradual spread south across the region today. Wet and breezy weather will dominate the rest of the week. Late Wednesday night through Thursday the coldest storm thus far this season is expected to bring significant travel difficulties to the Sierra Nevada. Also, recent burn areas should be alert for moderate rain rates early Thursday.
After a dry start to the week, wet weather returns to interior NorCal today. Radar shows a solid area of precipitation presently across northwest California along and ahead of the front. Varying amounts of clouds cover the region with patches of dense fog across portions of the Central Valley. Current temperatures are considerably milder compared to 24 hours ago, especially in the mountains, and range from the upper 30s to mid 40s in the mountains to the mid 40s to lower 50s elsewhere.
Mostly light precipitation will spread gradually south with the front today reaching the southern portion of the forecast area by late-afternoon or early this evening. Generally light showery precipitation lingers behind the front tonight and Wednesday. Some light snowfall accumulation may begin to stick around the northern Sierra passes late today and tonight as snow levels lower to around 6500-7500 feet and a winter weather advisory has been posted.
A potentially more impactful system is on the horizon for later Wednesday night and Thursday with heavier QPF, possible thunderstorms, gusty winds and heavy snow over the mountains with lowering snow levels. A winter storm watch continues for the northern Sierra and extreme southern Cascade Range. Somewhat drier and more settled weather returns Friday, but shower chances linger over the mountains.
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Extended Discussion (Saturday through Tuesday)
Next in series of Pacific Cold fronts forecast to push through northern California during the day on Saturday. This looks to be a moderately moist storm but snow levels continue to drop to what would be the lowest levels of the season so far so snowfall over the mountains could produce mountain travel issues.
If current forecasts hold, one to two feet of new snow will be possible over the higher elevations of the Sierra with this system. Large upper low remains over the western U.S. on Sunday so showers will remain a possibility although main threat will be over the mountains.
Cloud cover and cool airmass will keep daytime highs several degrees below normal. Building upper ridge off the coast and switch or more northerly flow should bring drying most areas Monday. Still kept a few showers possible over the Sierra Cascade crest but latest model runs keep precipitation out of the forecast area. Upper ridging over the west coast should bring continued dry conditions Tuesday with daytime temperatures warming up closer to normal.