The atmospheric Precipitable Water Vapour content (PWV) is crucial for astronomical observations in the infrared. In this work, we have validated the Weather Research and Forecasting (WRF) mesoscale numerical model as an operational tool for PWV at Roque de los Muchachos astronomical Observatory (ORM). We used radiosonde data obtained directly at the Observatory and at the sea level. An excellent agreement between PWV model forecasts and observations was found at both verification points with a correlation above 0.9.