What is the difference between a winter storm watch, a warning and an advisory? In these parts, an advisory is issued by the National Weather Service when a disruptive coating of 2 to 4 inches of snow —alone or with sleet and freezing rain — is anticipated. A watch means the possibility of hazardous conditions looms within 48 hours. A warning is for a mix-and-match set of circumstances: more than 5 inches of snow or sleet; one-quarter inch of ice; enough accumulation to down power lines; damaging precipitation and high winds.