The National Weather Service (NWS) issues alerts to inform the public about impending weather hazards. These communications translate meteorological data into actionable advice, promoting public awareness and safety. The goal is to provide a gradient of urgency, allowing communities time to prepare for potential impacts. Understanding the distinction between these alerts, especially those related to water, is fundamental to preparedness.
Defining the Flood Advisory
An Areal Flood Advisory is issued by the NWS when minor or nuisance flooding is expected or currently occurring across a general geographic area. This is the least severe alert in the NWS’s flood product line. The flooding is not anticipated to pose a significant threat to life or property, but focuses on inconveniences that can become problematic if ignored.
This type of flooding is typically caused by poor drainage, heavy rainfall over a short period, or urban runoff overwhelming storm sewer systems. It most often affects low-lying areas, underpasses, urban streets, and small creeks that may briefly overflow their banks. Although the water depth may be shallow, it can still cause minor damage or create hazardous driving conditions.
The advisory acts as a “Be Aware” message, emphasizing caution over emergency action. It is generally issued for short-lived events, with the water receding relatively quickly once precipitation stops. The advisory prompts residents to monitor conditions and avoid unnecessary risks in affected areas.
Understanding the Severity Scale: Advisory, Watch, and Warning
The NWS utilizes a three-tiered system—Advisory, Watch, and Warning—to communicate the severity and certainty of a flood threat. This scale moves from the possibility of minor impact to an imminent, life-threatening danger. The Flood Advisory, the lowest tier, signals nuisance flooding that necessitates caution but is not severe enough to warrant a warning.
The next level is a Flood Watch, which is a “Be Prepared” message issued when conditions are favorable for flooding to occur, but the event is neither certain nor imminent. A Flood Watch is often issued 6 to 48 hours before an anticipated event, giving the public a heads-up that the ingredients for significant flooding, such as a major rain system, are in place. This stage is meant for planning and assembling supplies.
The most serious alert is a Flood Warning, which is a “Take Action” message issued when flooding is either imminent or already happening. This level indicates a high confidence of severe flooding that poses a significant threat to life and property, often requiring immediate movement to higher ground. A Flash Flood Warning is a particularly urgent version, issued for rapid, violent floods that occur within six hours of heavy rainfall, common with intense thunderstorms or dam breaks.
The distinction between a Watch and a Warning is directly tied to the certainty and scale of the danger: Watch means the potential exists, while Warning means the danger is real and immediate.
Essential Safety Measures During an Advisory
When a Flood Advisory is in effect, the focus should be on practical steps to avoid inconvenience and minor damage. The most important action is to avoid driving through any standing water on roads or in underpasses. Just six inches of moving water is often enough to cause a vehicle to lose control.
Adhering to the principle of “Turn Around, Don’t Drown” is crucial, as the depth of the water is often deceptive and the roadbed underneath could be washed out. Homeowners in low-lying areas should move valuable belongings from basements or ground-floor storage to higher levels. Also, avoid walking near storm drains or culverts, as moving water can create dangerous suction forces.
The goal during an Areal Flood Advisory is to prevent a minor inconvenience from escalating into a dangerous situation. Exercising caution on the roads and securing vulnerable property helps individuals navigate this lower-level flood threat effectively. Staying informed via local media channels ensures awareness if conditions worsen and the advisory is upgraded.