Thanks.
Yes, the approximate tree line. Although I'm thinking about details, at this point I'm not planning them. I was trying to go with some washes first, as a foundation. Instead of water, though, I'm using a retarder media - basically a thinner that extends the drying time of acrylic. I'll try the same thing with the other elements, then build up colors and texture from there.
I ordered a 6-tube set of the artist quality water colors (Daniel Smith), but haven't opened them, yet. I also bought some empty half pans and an empty pan tin, then put some of the tube color into each pan - made myself pan set (once it all dries).