Weather alerts are a standardized system used to communicate the threat of meteorological events to the public. They provide timely information, helping people make informed decisions about their safety and daily activities. The system uses specific terminology to indicate the severity and certainty of a weather event. Understanding the difference between these terms is necessary for proper preparation and response to atmospheric hazards.
Defining the Weather Advisory
A weather advisory is issued when a hazardous weather or hydrologic event is occurring, imminent, or likely to occur, but the conditions are less severe than those that would warrant a formal warning. This alert signals that the event will cause significant inconvenience and, if caution is not exercised, could threaten life or property. Essentially, an advisory means the public should “be aware” and “exercise caution” due to potentially disruptive weather.
The National Weather Service uses an advisory to inform the public that conditions are hazardous enough to require a heightened level of awareness. It does not typically require immediate, life-saving action, but rather a change in routine or increased vigilance.
Understanding the Alert Hierarchy
The National Weather Service employs a three-tiered hierarchy of alerts—Advisory, Watch, and Warning—to communicate escalating levels of risk and certainty. The Advisory represents the lowest tier, indicating that hazardous weather is expected or occurring and requires caution and inconvenience-minimizing steps.
The middle tier is the Watch, which is issued when the risk of a hazardous event has increased significantly, but the exact timing or location is still uncertain. A Watch means that conditions are favorable for a severe weather event to develop, prompting people to be prepared and listen for further updates. For example, a Winter Storm Watch is issued when the potential for significant snow or ice exists within a 48-hour period.
The highest level of alert is the Warning, which is issued when a hazardous weather event is imminent or already occurring. A Warning means that weather conditions pose a direct threat to life and property, requiring immediate protective action.
Common Situations That Trigger an Advisory
Many different meteorological conditions can trigger a weather advisory when they fall below the criteria for a more severe warning. A Winter Weather Advisory is issued for minor snow or sleet accumulations, such as one to two inches of snow over 12 hours, or a trace up to a quarter-inch of ice. These conditions cause significant inconvenience, particularly for travel, but do not meet the criteria for a full Winter Storm Warning.
A Wind Advisory is issued for non-severe winds, typically sustained at 25 to 39 miles per hour or gusts up to 57 miles per hour. These speeds can make driving difficult, especially for high-profile vehicles, and may cause minor damage like downing small tree limbs.
A Dense Fog Advisory is issued when widespread fog reduces visibility to one-quarter mile or less, creating hazardous driving conditions. Heat Advisories are common when temperature and humidity reach levels that can cause heat-related illnesses, such as heat exhaustion, if proper precautions are not taken. Similarly, a Coastal Flood Advisory is issued when minor coastal flooding is occurring or imminent, often over and above normal high tide levels.
Taking Action During an Advisory
When an advisory is issued, the primary response is to exercise extra caution and prepare for potential disruption to daily life. People should adjust travel plans, particularly if driving conditions are affected by fog, wind, or minor winter precipitation, by allowing for extra travel time and reducing speed.
For advisories involving wind, secure or bring inside any loose outdoor objects that could become projectiles. If a Heat Advisory is in effect, practical steps involve wearing lightweight, light-colored clothing and increasing the intake of non-alcoholic fluids. Individuals should also reschedule strenuous outdoor activities to cooler parts of the day or avoid them altogether.
Staying informed is a practical step during any advisory, monitoring local news or a NOAA Weather Radio for updates and potential escalation to a Watch or Warning. Taking these minor actions can prevent a significant inconvenience from becoming a more serious incident.