No. My theory is wrong. The main module, which has run(myscene()) in the <i>middle</i> of it, completes before calling the scene . If I correct that import statement it downloads the weather maps, using the default parameters, and only switches to the scene once it reaches the webbrowser.open command at the end. (And it doesn't open the webbrowser window at all.)
So to enable this scene to collect parameters I need to move all the code after the run(myscene()) somewhere else so that it runs after the scene.