IMO the problem isn't the models but the accuracy of the input data and the sizes of the "cubes" of atmosphere it is possible to get data for and for the models to process in a reasonable timescale.
You can look at the ensemble sets to see that a slight variation in the input data makes a huge difference to the synoptics after just 2-3 days so it's no great surprise that the boundary of the heavy snow area in the NE USA was just a few miles out. The forecast for New England was spot on but I haven't seen much about that
I think saying accuracy beyond 96 hours is the same as it as in 1975 is pretty harsh. Just in recent memory, the snow in the Midlands and North (but nothing in the south) we had just around last Christmas was pretty well nailed about a week out before the little low pressure had even been formed. I don't think that would have been possible in 1975.
The problem is the failures to be 100% spot on every time and everywhere are much more widely commented on than the successes
Originally Posted by: lanky