In my experience, CAD is generally undermodeled, especially at long leads. If you go back to the ice storm that happened in western MD a few weeks back, the exact same thing happened out there — LR models underplayed the cold hanging on and as the storm got into the short range, the frozen kept hanging on longer & longer on the models. Obviously each setup is different but always best to look at climo & model “bias” when analyzing an OP run 160H+ out.