There's frequent questions about why MyRadar only shows radar for the recent past, but not the future. Recently, our weather science and data team put their heads together, and brought futurecast to the app! You can find it in the Layers menu, under the Radar settings menu.
For live radar data, MyRadar processes weather data from over 150 ground radar stations centered around the United States. Every 5 or so minutes, the ground radar station pushes out the latest weather data its recently collected. That push gets sent out to our servers, which begin processing the data so it can show up in the app itself. This process takes around 5-10 minutes to complete, hence the radar loop in the app itself stopping 5-10 minutes short of the current time.
If MyRadar is taking longer than 10 minutes to load new radar data, you might need to check some of your device's settings and internet connection. Here are a couple articles that could help:
Android: https://support.google.com/googleplay/answer/2651367?hl=en
Windows: https://support.microsoft.com/en-us/help/4027616/windows-check-your-network-connection-status