What happens to fronts over the western US?
The short answer is a lot, and it varies from case to case.
Let's begin with a loop of the front making landfall later today and tonight. This loop presents sea level pressure in black contours, 850 mb (1500-m) temperature in red contours, and either radar or 3-hour forecast accumulated precipitation in color fill. In this loop, note how the front appears to decelerate as it pushes inland across Oregon and northern California and ultimately takes on an "S" shape with the inflection near the trough that develops downstream of the Sierra Nevada.
By 1800 UTC 19 January, the front has a strongly distorted into an S-shape. One can quibble with the precise position of the cold front in my analysis over southern California and Baja California, but the S-shape is very clear in the temperature contours. Again, note the separation between the cold front and the model precipitation.
If you are wondering what all this means for snow, tough luck. I've already spent too much time on this post and need to get some work done! Maybe tomorrow. Maybe.