A Coastal Flood Advisory is a notification from the National Weather Service (NWS) that minor coastal flooding is expected or imminent. This alert is issued when water levels are projected to inundate areas that are normally dry. The severity is not expected to pose a serious threat to life or property, signaling a nuisance level of flooding. This typically results from a combination of high astronomical tides, persistent onshore winds, or a small amount of storm surge.
Conditions That Trigger the Advisory
The NWS issues a Coastal Flood Advisory when specific conditions align to produce minor inundation. Water levels are typically forecast to rise about one to two feet above the normal high tide mark, affecting the most vulnerable shorelines. This flooding is caused by ocean or Great Lakes water being pushed onto the land, not by rainfall. It often affects low-lying coastal areas such as beach access roads, coastal parking lots, and minor roadways closest to the water. The flooding is generally brief, non-life-threatening, and subsides quickly after the high tide cycle passes.
Understanding the Severity Scale
The Coastal Flood Advisory is the lowest rung on the NWS’s coastal hazard severity ladder, which helps the public understand the escalating threat. An Advisory indicates that minor or nuisance coastal flooding is occurring or imminent, requiring awareness and caution, but not immediate life-saving action. The key message of an Advisory is “Be Aware,” as the threat is confined to localized, low-lying spots.
The next level of alert is the Coastal Flood Watch, which is issued when conditions are favorable for moderate to major coastal flooding to occur, usually within 12 to 36 hours. A Watch means that significant flooding is possible, and such an event would pose a serious risk to life and property if the weather develops as expected. This alert is a signal to “Be Prepared,” as the potential for widespread and damaging flooding exists.
The most serious alert is the Coastal Flood Warning, which is issued when moderate to major coastal flooding is occurring or is imminent, typically within 12 hours. A Warning signifies an immediate threat where sea water is actively spilling over dune lines and sea walls, posing a serious risk to life and property. The message for a Warning is “Take Action,” as it requires immediate protective measures and potential evacuation due to the danger of the rising water.
Essential Public Safety Precautions
Since a Coastal Flood Advisory signals a nuisance-level threat, the public response focuses on common-sense measures and property protection. The primary action is to avoid driving through any areas where water has covered the road, even if the depth appears shallow. Only a few inches of moving water can cause a vehicle to stall or lose control, and the depth is often difficult to judge. Residents in low-lying areas should move vehicles from flood-prone coastal parking lots and streets to higher ground. Minor property, such as yard furniture or equipment located near the water line, should be secured or elevated to prevent it from being carried away.