I've looked at several posts and a few YouTube videos and I still have some questions.

I just got my 2013 RX 350 AWD last month. I put Blizzak snow tires on last Thursday but I have yet to venture into the snow. I believe that I am supposed to be at a full stop to push the AWD Lock button - which I do see a light for on the instrument panel when I do that. So, can I assume that I cannot engage it on the fly?

What about the Trac button - should I turn that off when I use the AWD Lock? Would it help or make things worse?

Thanks for your input. I don't want to wreck my beautiful (new to me) car!

 

The AWD lock button which locks the engine power at 50% front wheels/50% back wheels is only intended for "slower speed use".
In other words, once you engage it you do see the light on dash come on.
It does shut off automatically at 25mph which you have no control over.The light will turn off on its own.

In regards to TRAC button, you can leave it alone. Just leave it on unless you get stuck and need to generate some wheel spin.