The National Weather Service (NWS) uses a system of alerts to communicate the potential for hazardous winter weather conditions across the United States. These alerts notify the public when various forms of precipitation, cold temperatures, or wind may impact daily life and safety. Understanding the differences between these alerts, particularly the Winter Weather Advisory, allows people to prepare appropriately for approaching conditions. The advisory system provides timely notification so people can modify travel plans and take basic precautions before weather hazards arrive.
Defining the Winter Weather Advisory
A Winter Weather Advisory (WWA) is an official alert issued by the National Weather Service when hazardous winter weather is expected to cause significant inconvenience but is not severe enough to meet the criteria for a formal Warning. The advisory alerts the public to conditions that will likely create widespread travel difficulties and minor disruptions. These conditions are considered a hazard, but they do not pose an immediate or direct threat to life or property for the general population.
The advisory serves as a caution to travelers and residents, indicating that conditions such as slick roads and reduced visibility are imminent or already occurring. Forecasters issue the advisory to ensure people are aware of the need to exercise extra caution, especially when driving or spending time outdoors. The WWA is typically issued when there is an 80% or greater probability of the defined conditions occurring in the forecast area.
Specific Criteria and Thresholds for Issuance
The specific meteorological criteria that trigger a Winter Weather Advisory are not uniform across the country; instead, they are determined by each local NWS Weather Forecast Office based on the region’s climate and typical weather tolerance. An advisory is issued for snow, sleet, freezing rain, or a combination of these elements, provided the expected accumulation remains below Warning thresholds. For example, in a region accustomed to heavy snow, the advisory might be issued for an expected snowfall of 3 to 5 inches within a 12-hour period.
In contrast, an area that rarely sees winter precipitation might issue an advisory for any measurable amount of snow or ice because such an event would disproportionately impact commerce and travel. For freezing rain, the criteria typically involve the expectation of trace amounts up to one-quarter of an inch of ice accumulation, which is enough to make roads and walkways extremely slippery. Advisories can also be issued for blowing snow events that reduce visibility to less than one mile, often accompanied by sustained winds or frequent gusts.
Distinguishing Advisories from Watches and Warnings
The NWS uses a three-tiered system—Watch, Advisory, and Warning—to convey the severity and timing of potential weather hazards. A Winter Storm Watch represents the lowest level of certainty and is issued when conditions are favorable for a significant winter storm event to occur within the next 24 to 48 hours. The Watch indicates that the risk of hazardous weather has increased, but the exact timing and location are still uncertain, giving the public time to prepare.
The Winter Weather Advisory is the middle tier, signifying that hazardous conditions are either occurring or are highly likely to occur soon. This alert is less severe than a Warning because the expected precipitation or cold will cause inconvenience rather than an immediate threat to life and property. The conditions defined in an advisory are generally below the higher accumulation or wind-speed thresholds required for a Warning.
A Winter Storm Warning, representing the highest level of alert, is reserved for severe, life-threatening weather that is imminent or already happening. A Warning is issued for conditions such as heavy snow accumulation of six or more inches in 12 hours, or enough ice to cause damage to trees and power lines, which makes travel difficult or impossible. The crucial difference is that a Watch means potential severe weather, an Advisory means inconvenient hazardous weather, and a Warning means dangerous life-threatening weather requiring immediate action.
Preparing for Advisory Conditions
When a Winter Weather Advisory is in effect, the focus should shift to heightened awareness and practical safety adjustments, particularly for travel. Individuals should slow down while driving, increase the distance between their vehicle and others, and avoid sudden braking or steering maneuvers on slick surfaces. Check road conditions and consider delaying unnecessary trips until the advisory period has passed.
Preparation also involves ensuring personal safety if travel is unavoidable or if power outages occur. Keeping an emergency kit in the vehicle is recommended, containing items like blankets, non-perishable snacks, water, a flashlight, and jumper cables. Dressing in layers of warm, loose-fitting clothing is advisable when venturing outdoors to prevent cold-related issues such as hypothermia or frostbite. Monitoring local media and weather alerts provides the most current information, as an advisory can sometimes be upgraded to a Warning if conditions worsen unexpectedly.