Merrimack River Mouth Swell ForecastUnited StatesMAEssex CountyMerrimack River Mouth1-Day3-Day5-Day Graph Plots Open in GraphsSwell Height and Direction Forecast NOAA WaveWatch IIISwell Period Forecast NOAA WaveWatch IIIMerrimack River Mouth swell forecast issued today at 7:16 pm. Next forecast at approx. 7:40 pm.Get an account to remove ads