The National Weather Service (NWS) uses a systematic approach to communicate potential hazardous weather events, promoting public safety and preparedness. These alerts provide advanced notice of conditions that could impact daily life and create dangerous situations. Understanding the terminology behind these alerts is important for reacting appropriately to the forecast.
Defining the Advisory
A Winter Weather Advisory is an official NWS product signaling that hazardous winter conditions are occurring, imminent, or highly likely in a given area. This designation applies to weather events expected to cause significant inconvenience and potential hazards if ignored. An Advisory is less severe than a Warning, which indicates an immediate threat to life or property.
The intent of an Advisory is to encourage caution and awareness. While the weather is manageable, it presents substantial risk to travelers and those outdoors. Travel may become difficult or hazardous due to reduced visibility and slick roads, but it is generally not impossible. The Advisory acts as a formal notice that adjustments to daily plans, such as allowing extra commute time, should be made.
Specific Weather Criteria
The meteorological conditions that trigger a Winter Weather Advisory involve wintry precipitation accumulation that falls short of Warning thresholds. Typically, this involves lighter snowfall totals, often ranging from one to four inches over a 12-hour period. The exact amount varies based on location; a small amount of snow in a southern city might warrant an Advisory, while a mountainous region would require higher totals.
The Advisory may also be issued for light amounts of freezing rain, generally defined as a trace up to a quarter-inch of ice accumulation. Conditions like sleet, freezing drizzle, or blowing snow that reduces visibility, but not severely, can also prompt an Advisory. Local NWS offices set these criteria, ensuring the alert reflects the impact of weather on a particular community and accounts for local infrastructure.
Understanding Alert Severity
The NWS uses a three-tiered hierarchy for winter weather communications: Advisory, Watch, and Warning, each indicating a different level of severity and timing. The Winter Weather Advisory is the least severe, focusing on conditions that present considerable inconvenience but are not expected to cause widespread disruption or pose an immediate threat to life. It indicates conditions are occurring or imminent and require caution.
The next level is a Winter Storm Watch, issued 12 to 48 hours in advance when conditions are favorable for severe winter weather to develop. A Watch signifies that a storm is possible and encourages the public to monitor the forecast and prepare for potential danger. The highest level is a Winter Storm Warning, which means a significant, life-threatening event is occurring or is about to occur. A Warning demands immediate action to protect life and property, as travel will be difficult or impossible due to heavy snow or ice accumulation.
Practical Steps to Take
When an Advisory is issued, the focus should shift to minor adjustments and increased caution rather than significant cancellations. For those who must drive, traveling slowly and allowing extra time to reach a destination is the most important step. Vehicles should be prepared with a full tank of fuel, a charged mobile phone, and a basic emergency kit containing an ice scraper, blankets, and non-perishable snacks.
Individuals should dress warmly in layers, choosing loose-fitting clothing to maintain body heat if spending time outdoors. Avoid overexertion from strenuous activities like shoveling heavy snow, as the combination of cold temperatures and physical strain can increase the risk of heart-related issues. An Advisory is a prompt to be aware of the environment and proceed with vigilance.