When we make forecasts for 24-72 hours out, it is typically very accurate. To show you the difficulty of forecasting, I want to show you what we call "Ensemble" maps. Ensemble forecasting is a technique that takes several different datasets in attempt to obtain a representation of a storm system or pattern. Below is the GFS Ensemble spaghetti plot for 24 hours from now. It looks nice, neat, and in order. Forecasting 24 hours out, is not too difficult. The blue lines are the 540 decameter 500mb lines. (Roughly, the rain/snow line in a perfect world). It's pretty easy to point out the troughs (u-shaped features) and ridges.
We'll continue to try our best to nail the forecast, 7 days in advance!