Hi Ted! Great topic!
I've come across similar problems on the Thompson, on a run we call the Spur. At the top end it is a drop off backed up against a steep bank, and often a nasty wind is blowing downriver. A snake roll is a great call here except that you invariably end up catching your loop in the rocks and brush behind you. I think in this situation (as in pretty much any situation) it again comes down to what you are used to and comfortable with, rods included. A long belly line will work, as will shooting heads of various styles and lengths.
There are a few downsides to long belly lines in such situations, though. The added length of line moving around in a wind acts like a big sail, making it a little more challenging to manage, and it gets tricky using a sidearm cast (to help you beat the wind) with a long belly line because you really have to manage your D loop well and nail your timing; a shooting head gives you a real advantage whenever you are forced to drop your rod tip such as in a side arm cast, because the D loop can be smaller and more compact yet is more easily managed and will effectively load your rod. Another downside to a long belly in such a situation is the overall belly length needed to make a fishing cast. In tight quarters if you are using a long belly line and have to resort to shooting line anyways to hit your target, it doesn't make sense to fight the added weight and friction of the line belly shooting through the rod rings when running line is more efficient.
If I was forced to cast off my upstream side, my solution in this situation would be a classic shooting head and a Perry Poke-style set up with a bit of a kick to it, but with a lower rod position to keep things under the wind, followed by a low sidearm delivery cast. My moves would have to be accelerated to fight the downstream wind, and I'm going to use that kick I mentioned in the upstream positioning of the line to perhaps throw the line a little farther above me, again to help me beat the wind. Otherwise I would use a snake roll or triple spey off my opposite shoulder, being sure to anchor the line well out in the river and minimize the size of the loop behind me.
If I chose a long belly line for these conditions, I think my cast would be the double roll aka the contrived loop (I've also heard it called the Armenian cast) either off my downstream shoulder or reversed. Using this cast might minimize the need to lean too far out as you can make it in very tight quarters with little line behind you. It's a cool cast and great for a long belly line.
But no matter which system I use I'm going to thrash and splash around a lot initially adjusting to the conditions, so the steelhead will probably leave anyways, and probably so should I, but it's great casting practice.