The National Weather Service issues a variety of products to keep the public informed of weather changes. In addition to our daily forecasts, we may issue additional products including special weather statements, watches or warnings in anticipation of weather events. These products have differences in significance depending on how much time we have before the event, how sure we are of an event and how big an event we are anticipating. The following are some of the products we issue during the winter and their significance as they apply to the forecast.
Winter Storm Outlook: A winter storm outlook is issued several days, typically 3 to 5 days, before we anticipate the potential for a major winter storm. This outlook simply states that there is the possibility for a major snow event in a few days. We typically issue a Winter Storm Outlook when we think there is a 30 percent chance or more of a major snowfall. In the National Weather Service, we define a major snowfall as 7 or more inches of snow in 12 hours or 10 or more inches of snow in 24 hours. When a Winter Storm Outlook is issued our listeners are advised to keep in touch with our forecasts for the potential that a Winter Storm Watch or a Winter Storm Warning may be issued.
Winter Storm Watch: A Winter Storm Watch is issued a couple days, usually 2 to perhaps 3 days, before we anticipate the possibility of a major winter storm. A watch only means that a major snowfall is possible. Listeners should stay tuned to our forecasts for the potential that a winter storm will be issued.
Winter Storm Warning: A Winter Storm Warning is issued when we are confident that a major winter storm is coming, typically within the next day or two. The public should take appropriate action to prepare for heavy snow. This may include picking up extra groceries, filling the blower with gas, and canceling or postponing any travel that’s not absolutely necessary.
Winter Weather Advisory: A Winter Weather Advisory is issued to alert the public of a moderate snowfall. Our criteria for an advisory ranges from an average of 4 inches of snow to an average of 6 inches of snow in a 12 hour period. If we expected more than 6 inches of snow in a 12-hour period, we will issue a warning.
Freezing Rain Warning: A freezing rain warning is issued when we expect a half inch or more of freezing rain to occur. This can result in very hazardous road conditions and the downing of trees and power lines.
Freezing Rain Advisory: A freezing rain advisory is issued when a trace or more of freezing rain is expected, but less than half an inch is expected. Light amounts of freezing rain can still result in very dangerous travel conditions, but will not be likely to result in downed trees and power lines.
Wind Chill Warning: A wind chill warning is issued when very low temperatures combined with wind are expected to result in wind chill readings of 35 below zero or lower. Wind chill readings this low can be dangerous, causing frostbite on exposed skin. Hats, gloves, layers of warm clothing and limited exposure outdoors are advised.
Wind Chill Advisory: A wind chill advisory calls for wind chill readings 20 below zero or colder, but not down to 35 below zero. Dress very warmly and limit exposure to the wind.
High Wind Warning: A high wind warning is issued when sustained winds of 40 mph or more are expected, and/or frequent gusts of 58 mph or more are expected. There is a significant risk for downed trees and power lines. Prepare for a potential power outage. Make sure you have batteries, candles, matches and extra bottles of water. If your heating system depends on electricity, you may want to keep a kerosene heater and some K1 kerosene fuel as a backup.
Wind Advisory: A wind advisory is issued when winds between 30 and 39 mph are expected and/or frequent gusts between 48 and 57 mph are expected. Isolated tree damage and power outages are possible.
National Weather Service product headlines are designed to alert the public to weather that may impact the region in a significant way. Understanding what these headlines mean and how these headlines are used to highlight specific weather hazards is important for understanding our forecasts. We hope everyone will have a safe and warm winter as we keep watch on the weather this coming season.
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