Calling Web services

I am about to start using the API, I tested the sample request provided at the doc page:

http://flightxml.flightaware.com/json/FlightXML2/MetarEx?airport=KJFK&startTime=0&howMany=1&offset=0

I get the error Authentication Required however I am sending the basic auth params as indicated:

User: [my flightaware.com username]
Password: [my API key] - it has permissions for FlightXMLVersions: v3

Could you please advice?

The MetarEx function is not currently available on FlightXML 3.0 Beta. You can use FXML2 to receive Metar data for an airport.

use https://flightxml.flightaware.com/json/FlightXML3/WeatherForecast and pass the airport code in with the api call