We lived in Davis for years so know what winter storms in the Valley are like. Things you need to consider: Traction, winds, visibility. The combination of wind and reduced traction can be very serious. I imagine that sway control is very important as would weight distribution.
Tire inflation is critical in wet conditions: http://www.tirerack.com/tires/tirete...e.jsp?techid=3
As this article says speed is also critical.
So, make sure your tires are properly inflated, slow down, and watch out for gusty wind.
If it doesn't feel safe, it isn't. Stop and wait it out.
In late October this year while heading back to California we got caught in a small overnight snow storm in Western Nebraska. In the morning it was no longer snowing so we headed out and started across Wyoming. After a few miles, I just wasn't comfortable with the combination of winds, wind gusts, and road surface. So I pulled off on a freeway ramp and parked. The ramp was full of tucks and commercial transporters hauling trailers and fifth wheels.
Waited until it had warmed up and dried off a bit and then headed out.
During the drive across Wyoming we saw at least 15 semi's, TTs, and Fifth Wheels that had gone off the road. Damage varied from just needing a tow back onto the road to complete disasters with the box off the bed of the semi trailer and a fifth wheel that had completely crushed its tow vehicle.