yeah, a 20" storm is probably what, a one in 10 year event, maybe one in 15 year event depending on where you are? that's just the reality of how things are at our latitude.
the ETA model is basically the predecessor to the NAM - and, I think it was DT who said if you had agreement between the ETA and the Euro, it was basically a lock (this has not surprisingly been proven NOT to be the case always, but still).