“天气预报”用英语怎么说?（请进）

“天气预报”用英语怎么说?（请进）
我记得是weather forecast
怎么今天我看了一篇文章上面用的是weather forecasting
原句：Few people know that it was Franklin who discovered the movement of storms from west to east upon which all weather forecasting today has been based.
到底用哪个对?
或是说什么时候用这个,设么时候用那个?
请指教.