cold water, wind, air temperature and vessel movement. Heavy freezing spray watch (MWS) – Usually issued for shipping interests when conditions are favorable for a heavy freezing spray event meeting Heavy Freezing Spray Warning criteria but its occurrence, location, and/or timing is still uncertain. Freezing spray advisory (MWS) – Usually issued for shipping interests when conditions are probability of accumulating frozen sea spray on vessels of less than 2 cm per hour caused by some combination of cold water, wind, air temperature, and vessel movement. Hazardous seas warning (MWS) – Significant wave heights and/or wave steepness values—independent of strong winds—are forecast to cause rough surf in the warned coastal area and adjacent waters, which could pose a serious threat to vessels that do not move to stable waters or dock. Warning criteria may vary depending on the NWS Weather Forecast Office. Hazardous seas watch (MWS) – A rough surf event—regardless of forecast wind speeds that may contribute to such an occurrence—is possible in the warned coastal area and adjacent waters, but its occurrence, location, and/or timing remains uncertain. Warning criteria may vary depending on the NWS Weather Forecast Office. Low water advisory (MWS) – Critically below average water levels over the Great Lakes, coastal marine zones or other tidal marine area, waterway, or river inlet within or adjacent to a marine zone have been observed, and potentially present a hazard to maritime navigation. Marine weather statement (MWS) – The equivalent of a special weather statement at sea, indicating potentially hazardous marine conditions. Special marine warning (SMW) – A warning to mariners of short-duration hazardous weather conditions (lasting up to two hours) including thunderstorms or squalls with wind gusts of or more, hail diameter or larger, or waterspouts affecting coastal areas not adequately covered by existing marine warnings. Short-duration mesoscale events (such as a strong cold front, gravity wave or squall line) expected to last two hours or less and produce criteria wind speeds, or volcanic ashfall may also warrant issuance. Particularly dangerous situation special marine warning (SMW) – A warning to mariners of hazardous weather conditions that present a considerable threat to life and property. Small craft advisory (SCA) – A warning to mariners of high sustained winds or frequent gusts and/or significant sea or wave heights that may damage or capsize small boats. Only issued by WFOs in coastal regions and the Great Lakes for areas included in the