Why do others often fail forecasting weather 1-2 days out?
The weather forecasts most others make start failing as soon as the forecast is made and continue to get worse the further out they go. This is because they are not sure how the forces that cause our weather are going to change from hour to hour and day to day. The weather you will get in 7 days is most often not well understood by the weather forecaster until it gets much closer. Our weather forecast calculations do not change from our original calculation, so there is no need to change them.
