Actually, you’re very close to being able to do this since you’re already uploading to the Weather Underground. You just have to sign up for CWOP to get your station identifier. (see link below). That’s how to make your personal weather station Official. After you do that, your data will be available to everyone using the NWS; including respective forecast data. Just add the NWS integration with your new Station ID.
Here’s the Llnk.
“If you are already sending data to internet sites (like Weather Underground), then all you will need to do is sign up with CWOP, receive a unique station identifier, and make a few minor configuration changes within your weather station’s software to tell it to send your data to the CWOP (see the instructions manual)”
PS: I read that some Ecowitt owners use Cumulus MX to upload the data. What software do you use to upload to the Weather Underground?