MyRadar is a doppler radar weather app, as opposed to a satellite image weather app. This means that we rely on data from land-based radar sites rather than a satellite that can see the weather worldwide. It's also how we can show such granular detail in the Professional Radar Pack.
Currently, MyRadar provides radar coverage for most of the world. Previously we only had North America, Japan, Korea, and Europe, but we just rolled out a new satellite-powered enhancement that allows us to render radar for most of the world. It's fairly new new, so there's still areas that aren't covered, such as much of Russia and the arctics.