Since Wunderground PWS data submitters can now (as of 19-Feb-2019) get an API key for the api.weather.com site, I got a key yesterday and started work on a WC-forecast.php script based on the prior WU-forecast.php script.
I also got a new key and am working on a WC-forecast.php script (based on the old, soon to be deprecated WU-forecast.php script).
I initially couldn't get a key with Firefox, but was successful with Chrome (after signing in to my WU ID).
Missing from the returned JSON is a timestamp representing WHEN the forecast was done.. only a 'validfrom' date set was found. Also missing is any meta-data about location name. It's also only a 5 day forecast (10 icons).
The language stuff works just fine and returns UTF-8 text in the requested language.
I'll let you know when the script is ready for beta testing.
I've done a preliminary mapping of their icon codes to icons used with the NWS/Saratoga and Meteotriviglio sets.