December 16, 2016 – Showers ending over the Sierra today with only light additional snow accumulations. Freezing temperatures in the valley this weekend with dry conditions. Mainly dry next week except for a chance of light showers during mid week. A better chance of rain most areas by next Friday.
Discussion
Satellite and radar indicating that the back edge of the cold front that brought significant precipitation to northern California on Thursday is now near the California Nevada border. Scattered light showers continue behind the front over the Sierra Cascade range. It appears from surface observations that snow levels over the 80/50 corridors of the Sierra have dropped to between 5000 and 6000 feet.
Upper troughing over the Great Basin will produce cyclonic flow over the Northern Sierra so a threat of showers will continue there through the day. Cold air behind the front will bring a significant drop in snow levels today but additional snowfall will be quite light.
A 6 mb surface gradient has developed between MFR and RDD this morning and a northerly wind has begun from about Chico northward and this northerly flow will spread southward today. Partly cloudy skies and a very cool airmass will keep daytime highs today a few degrees below normal.
High pressure pushing in over the state will bring clearing skies over night. These clearing skies combined with a cold airmass will bring cold overnight temperatures to the north state tonight. Overnight minimums in the Sacramento valley will drop to around or below freezing.
Short range models are showing a little fog from about Sacramento southward where winds will be lighter and ground moisture is plentiful from recent rains. Temperatures warm a little Saturday under mainly clear skies but still come in a little below normal.
Surface winds weaken a little Sunday morning compared to early Saturday so Sunday morning could see slightly cooler temperatures still. Daytime highs will warm a bit more on Sunday under the ridge reaching right around normal for this time of year. The warming airmass should keep minimum temperatures in the valley Sunday night at near or above the freezing mark.
Monday will see continued mostly sunny skies with daytime highs edging up just a bit more but still staying right around average for this time of year.
Extended discussion (Tuesday through Friday)
Short wave trough moves through PacNW Tuesday with southern portions of wave bringing a slight chance of showers over the northern interior mountains. Short wave ridging moves through Wednesday for dry forecast. Stronger Pacific frontal system progged to move into Interior NorCal towards the end of next week. Models continue to show differences with timing and strength of system. However, both GFS/ECMWF showing fairly widespread precip possibility with this wave Thursday into early Friday, so have trended POPs up for this time period.