This is a good list. I'd just add a small tarp to lay on the ground when putting on traction devices.
From the US National Weather Service:
More & more model guidance suggests we will enter a colder weather pattern either this upcoming weekend or early next week. Our best statistical guidance suggests the probability of at least 1" of snow falling on the valley floor is >50% late in the weekend or early next week. While it's too early to tell if this will come to fruition, this is a very high probability for snow on the valley floor one week out so please continue to monitor the forecast this upcoming week & consider altering travel plans accordingly. Widespread winter travel conditions are very much a real possibility across much of the Pacific Northwest this upcoming holiday weekend and/or early next week.
Also, keep in mind that Clackamas County maintains warming centers, which you can find at this link.