Currently weather stays in the exact same spot at the same intensity for very long periods of time. What if the weather was more dynamic and alive. Gradually meandering around the map growing and shrinking in size randomly. They could also pop up out of nowhere and you could watch them grow and then gradually fade away.
Also, just having them as one perfect circular area is probably much easier to implement, but if it's just a boundary for where the weather starts, then the boundary could be made up of many points moving somewhat independently of each other. growing and shrinking the entire weather system based on a random seed in each point. Though completely random wouldn't be as interesting as weather having a very slight bias to go near specific airports who's geography happens to lend itself to more inclement weather occurring.
Different levels of intensity of weather should be based on if there is other weather surrounding it, just like how it is now. Where a yellow area can only be inside of a green and a red can only be inside of a yellow. Heavy storms should happen if a storm happens to spawn inside of another storm, though a bias for storms being created inside of already existing weather should be added so that severe weather does actually occur somewhat more regularly than pure chance will allow.
The weather has felt pretty static and having to choose jobs based off of what you think the weather will do and if that will make a certain job harder than another. You might have to modify a flight plan in the last few minutes because the weather started to deteriorate, it would add another layer of complexity to decision making.