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 today at 12:48 pm. Next forecast at approx. 12:48 pm.Get WillyWeather+ to remove ads