December 4, 2018 – Chances for light precip through Wednesday night. A stronger system may impact the area early next week bringing heavier rain and mountain snowfall.
Discussion
It`s considerably milder across the region early this morning as clouds stream up from the southwest ahead of the offshore system. Current temperatures are running 5-15 degrees warmer compared to 24 hours ago and range from the mid 20s to mid 30s in the mountains to the mid 40s to lower 50s across the Central Valley. The warm-advection ahead of the system is resulting in some light precipitation across the northern mountains and northern Sierra.
The offshore system is forecast to slowly fill as it tracks gradually southeast the next several days, reaching SoCal/northern Baja by Thursday night or early Friday. The best chance of precip across the forecast area is expected to occur tonight and Wednesday as the deformation zone sets up across NorCal.
Overall, QPF will be light with amounts mostly less than a quarter inch expected across the valley with around half an inch to three quarters of an inch over the mountains (higher amounts to the west over the Coast Range). Snowfall is mostly expected to be in the 3-6 inch range above 5000 feet.
Drier weather will to return Thursday and Friday as the low moves further to the south.
Extended Discussion (Saturday through Tuesday)
Upper level ridging over Northern California continues Saturday morning, before a system moves towards the area by the afternoon bringing chances for precipitation to the coastal range. QPF amounts remain quite light Saturday into Sunday.
Sunday night, models are honing in on a cold system which will likely bring heavy snow to the mountains. For now, snow levels look to begin above 5000 feet, dropping to 4000 feet Monday. Travel impacts seem likely with over a foot of snow forecast for most areas. Models still disagree on the strength and exact timing of the system, although it looks to linger through at least Tuesday.