January 11, 2020 – Multiple weather systems are expected to impact the area through next week bringing rain and snow to northern California. Lingering light mountain showers continue today with a break possible tonight before an extended period of unsettled weather impacts the region starting Sunday. Cold storm systems will bring gradually lowering snow levels.
The weather system forecast for Monday night will likely bring mountain travel impacts to northern California, extending into the upper foothills. A stronger storm is possible Wednesday night into early Friday with periods of Valley rain and heavy mountain snow that could cause road closures. Low snow levels are expected and these could bring impacts for the foothills and over portions of I-5. There is some potential for snowfall to extend into the Redding area late in the week. Stay tuned as details on storm timing and snow amounts develop!
Discussion
The upper level trough is dropping south through the Pacific Northwest, swinging a weak disturbance over Norcal this morning. Light precip has been observed in some areas so far, and with the rest of the system just entering the coastal range at this time. Precip chances will linger through mid to late morning, with snow levels being around 4000-4500 feet. 2-4 inches of fresh snow can be expected for elevations above 4000 feet with light rain expected else where. As the trough continues to push eastward, conditions will dry out for the Valley while the mountains hold on to chances for additional light snow showers through early Monday morning. Elevations above 4000 feet may see an additional 1 to 3 inches of snow. We`ll see a brief reprieve in shower activity for most of Monday, with the next more significant system arriving later in the day. Snow levels with this system appear to dip down to 3000 feet, and while there is still some uncertainty and model differences with this system, mountain travel delays are seeming more likely late Monday night into Tuesday morning. Better details will come in line for this system over the next few model runs. Showers should taper off Tuesday with mountain showers lingering into Wednesday morning.
Extended Discussion (Wednesday through Saturday)
We are going to remain in an active weather pattern as we head into the extended period. We will see zonal flow with lingering mountain showers on Wednesday.
An upper level trough will be digging into the region as we head into Thursday. This trough will be able to pull in more moisture than the systems earlier in the week. There is some disagreement in the ensembles mainly when it comes to timing, the GEFS is a bit slower with it but both global ensembles have similar tracks. Widespread rain and snow is expected Wednesday night into Thursday afternoon as we see a cold front push south through the area.
This system will have quite a bit of cold air with it and it’s looking like we will see very low snow levels between 2000 and 3000 feet. Given the low snow levels this will likely be a high impact storm and could result in road closures especially on Thursday. Multiple feet of snow will be possible in the mountains and snow accumulation can not be ruled out in the upper foothills. Details with this system will likely change as it gets closer but if you have mountain travel plans for the mid to late week you will want to monitor the forecast closely and be prepared to adjust your plans accordingly.
Drier conditions set in for Friday but we will continue to see lingering mountain snow showers as zonal flow returns. Snow levels look to rise to around 3500 feet. Overall additional accumulation will be light with another few inches. Temperatures will be running below average but will warm to near average by next weekend.