Stefano, Due to limitations in the X-Plane SDK, the surrounding clouds around you are depicted on your current METAR positions. Far out formations will not remain. This has been around since v1 of SMP, and is simply because we don't have the access we need at this time to correct the behavior. We have a few ideas in place to solve this. They are major workarounds, but for now things are status quo and what you're seeing is nothing new.