Bring your wheel chains (std. equipment for NE LA riverbottoms, but also work great for snow); come along, if your vehicle is not winch equipped, and extra cable, chain, etc. as mentioned in a previous post, unless you can attach to another vehicle. Not as many trees in some parts of WY as there are in Ouachita and Union parish!
WY weather is like CO, in my experience. I have been there when shirt sleeves were too hot, and when the snow was knee high to a giraffe at the same time of the year. Pack clothing you can layer. The new garments are great, but expensive. Wool, poly pro, and down are old school, but still work. Avoid cotton, if you are not having summer heat, if possible. The mountaineers have the saying "cotton kills" for a reason. I just bring all the clothing I own and hope for the best (LOL)! You will hear a lot about boots, but if the weather is sloppy, the old LaCrosse Burley with the Air Bob sole will serve you well.
I think you should reconsider your decision about the spotting scope. This trip is going to be a big investment, and without a spotter, you will be missing a key component. You have some good quality optics, but nothing that will take the place of a spotting scope. Perhaps you can borrow one, or pick up one of the less expensive spotters for the interim. Burris, Leupold, Bushnell, etc. all make nice inexpensive spotters that can be had for under $250. I picked up a Burris in a silent auction last year, and it is excellent for the price. It is not a Zeiss, but will serve you well on this hunt for about 10% of what you will pay for a top of the line spotting scope.