Why radar extrapolation cannot be used for long-term weather forecasting

Because the data is real-time. Places with relatively strong radar callbacks have strong convection (hail, strong winds, heavy rain, etc.). However, the data detected by radar are all real-time, and the weather of the next time can only be judged based on the retracement movement and size development of the previous time. The weather can only be forecast for three to six hours. But it is indeed more practical for summer.