http://wasatchweatherweenies.blogspot.com/2017/03/major-upgrades-to-nam.html

The NWS modeling people (NCEP) made some significant changes and
updates to the NAM modeling suite effective 03/21 or 03/22. These changes were
announced several months ago and a chance was given allowing user web services
to test their code. I notified Dr.Jack recently. It looks like changes to the NAM
13KM grid files should have been minimal. But, whenever there are big production
suite changes, inevitably it breaks something in the user code. Dr.Jack and
Chris Ghali of XCSkies will probably figure it out in time.

These changes are called NAM v4 and it will be the last of this system.
Development will be frozen from here on out. The 13km NAM remains with the same
13km resolution and forecasts out 84 hours but with numerous physics and
production changes. The NAM high resolution model now runs at 3km instead of 4km
with hourly output to 60 hours.

Don't complain to NWS about this... support your local soaring web services
provider.

Thanks to Ron Gleason.