With sensor array spread over large enough area you can measure rainfall and direction of storm travel. Still, the storm can quit before it reaches your site, or it can start raining at your site first. There are many other factors still to consider (ie. terain, fronts, etc.). Just ask the National Weather Service (USA) and you'll see how hard it can be. Here a large government agency with loads of resources still can't get it right all the time. I have seen microwave and lidar systems that can give you a little more warning, but even those aren't fool proof. Where I live we often get rain that evaporates before hitting the ground (Virga). You can see it raining, but your dry!