December 23, 2019 – A few showers linger over the mountains, but most of the Central Valley will be dry early this week. Another weather system will bring a chance of showers to the region on Christmas followed by dry weather this weekend.
Elongated upper trough lingers today as stronger energy digs to our south toward SoCal. Clearing skies have allowed areas of dense fog to develop across the Sacramento Valley from south of Red Bluff to around the Sacramento area. Developing northerly flow may push fog and stratus south into the northern San Joaquin Valley early this morning, and also allow for clearing of fog by late morning.
The trough remaining over the area may allow for enough weak convection for lingering scattered showers over the northern Sierra Nevada and foothills. Less activity is expected Tuesday as the current system lifts out to the northeast ahead of more upstream energy moving into the region and reinforcing the large trough over the western US. Generally light QPF with relatively low snow levels (2-3k ft) is expected on Christmas.
Drier northerly flow returns beginning Thursday setting the stage for colder overnight temperatures and potentially more widespread morning frost potential across the Central Valley.
Extended Discussion (Friday through Monday)
Upper level ridging will be in place for the start of the extended period. This will bring quiet and dry weather with partly cloudy skies. The upper level ridge will push east during the day Saturday as a trough approaches the area from the NW. Ensembles keep the trough axis just to our west and dig it down the CA coast. This scenario would keep the better forcing to our west but we would still see light scattered showers across the area starting Sunday morning continuing into Sunday night. This will be a cold system with low snow levels, likely in the 3000 foot range. It will not have a lot of moisture to work with and that will keep QPF light. Overall it is expected to be a low impact system despite the low snow levels. Upper level ridging builds back in Monday as the trough continues to push south down the coast. Temperatures will be near average throughout the period except for Friday night when we see cold overnight lows.