Coastal Flood Warnings - Issued when the combination of the astronomical tide and the storm surge will result in flooding of coastal areas. Onshore winds associated with large storms contribute to this type of flooding. To help determine the potential for flooding, the National Weather Service Office in Gray continually monitors hydrologic conditions throughout New Hampshire and Western Maine. River statements are issued daily and contain forecasts of the water levels for the major rivers in the area. Also, during the late winter and early spring the National Weather Service, in coordination with other federal, state, and local agencies and cooperative observers, surveys the snowpack in the area to determine the potential for spring flooding.
Ice jams can also cause flooding during late winter and early spring.
Be alert to any rapid rises or falls in the river levels. A rapid rise in a river level may indicate that an ice jam has formed downstream of you. In contrast, a rapid fall in a river level may indicate that an ice jam has formed upstream from you. If an upstream ice jam breaks up rapidly, flooding of downstream areas can occur quickly. As little as 6 inches of rapidly flowing water can cause some cars to be washed off the roadway.