Black Rock Sands Porthmadog Swell ForecastUnited KingdomWLGwyneddBlack Rock Sands Porthmadog1-Day3-Day5-Day Graph Plots Open in Graphs Swell Height and Direction Forecast NOAA WaveWatch III Swell Period Forecast NOAA WaveWatch IIIBlack Rock Sands Porthmadog swell forecast issued yesterday at 11:50 pm. Next forecast at approx. 11:50 pm.Get WillyWeather+ to remove ads