Tire pressure is only one consideration when driving on snow-covered trails presumably where no vehicular traffic has packed the snow. The original poster also said he has BFG MT's. MT's will tend to dig into the snow more than AT's so flotation (ie. lower tire pressure) will be more important. Figure that the snow is covering wet dirt (i.e. very shallow mud) so reduced tire pressure is also a good idea. Also, the big lugs will tend to self-clean better than AT's.

Last winter I wheeled in the Sierras (which is a few hours east of the topic starter's location, Stockton) and even with aired-down tires (BFG ATs) my buddy and I both got stuck several times, requiring tow straps and/or winching.

The bottom line is that even if you run the "ideal" tire pressure, whether high or low, you can still get stuck: high-centered on your underbelly, all 4 tires spinning away.

One last tip (since that's what you asked anyway): wear clothing appropriate for being out in snow. Do not make the mistake of believing that just because you're driving, not hiking, that you won't actually have to get out of your truck and walk around in the snow. It's gonna be you, after all, that has to hook up that tow strap.