Overall accuracy two hours ahead: 97.5% averaged over May and June, 2007 for the NE states.
AquaScope forecasts are automatically and continuously verified by comparing radar precipitation "right now" with the forecasted precipitation from two hours ago. Judged in terms of where you can stand, AquaScope generates on the order of one million separate forecasts every ten minutes. Each forecast two hours ahead is counted as correct if the predicted outcome (precipitation/no precipitation) happened within plus or minus fifteen minutes. Overall accuracy is then all correct forecasts versus all forecasts, scaled as a percentage. To see AquaScope's current overall accuracy, click on the link below.
Here is a closeup from one verification image comparing "now" with the forecast from two hours ago: white and black indicate good forecasts for precipitation and no precipitation respectively, blue represents current precipitation that was not predicted, and red represents forecasted precipitation that didn't happen (pink at the top left indicates no forecast available).