72 hours is the lock in point for forecasts and are often the most accurate up to about 3-4 hours before. The models do all sorts of jankity stuff inside of 72 hours because of the increased resolution. That is why the forecast went all over the place early saturday, shifting the storm around by up to 6 hours. By Wednesday people knew it was going to be heavy thunderstorms...and considering the 8-15 mile rule, and 30 minute wait...heavy storms for extended time equals rainout. The type of system it was also destined it to be a rainout, a stalled front does not move through like normal systems, but funnels energy into highly moist areas, that is why the storms strengthened as the night went on, not vice versa.