If you read the discussions here, radar "forecasting" is a very controversial feature. That's due to it not really being a forecast. Instead, it's just an extrapolation, where we take the current images from a radar, calculate the movement vectors of different features and show how the situation could look if the features kept moving in the same direction and at the same speed during the next hour.
However - it will not show new phenomena that could emerge and it assumes that they will not disappear. It's a feature that is really popular in some regions, where it is a good predictor of rain or thunderstorms which are coming in the next hour. However, in other regions, with different geography, it can be less useful. For example, it's good for people who live in a single spot and know how storms tend to behave as they approach from different directions. However, without this local knowledge, you really cannot rely on it even within a 1h timeframe. A 3 hour radar extrapolation would basically be complete fiction.