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Brochures, Booklet and Related resources

Frequently Asked Questions about Winter Weather

+A major winter storm is moving up the East Coast. How is it monitored and forecast?

+Winter weather Watches, Warnings and Advisories: What do they all mean

  • Winter Storm Watch: A watch means that severe winter conditions, such as heavy snow or ice, may affect your area, but where, when and how much is still uncertain. NWS issues a watch to provide 12 to 36 hours notice of possible severe winter weather. A watch is intended to provide enough lead time for you to prepare.
  • Winter Storm Warning: NWS issues a warning when its scientists forecast 4 or more inches of snow or sleet in the next 12 hours, 6 or more inches in 24 hours, or 1/4 inch or more of ice accretion.
  • Winter Weather Advisories: inform you that winter weather conditions are expected to cause significant inconveniences that may be hazardous. If caution is exercised, advisory situations should not become life-threatening.
  • Blizzard Warning: let you know that snow and strong winds will combine to produce a blinding snow (near zero visibility), deep drifts, and life-threatening windchill.
Be sure to listen carefully to the radio, television and NOAA Weather Radio for the latest winter storm watches, warnings, and advisories.

+Why is predicting the exact amount of snowfall so challenging?

Snow forecasts continue to improve, but they remain a challenging task for meteorologists. Heavy snow often falls in small bands that are hard to discern on larger resolution computer models. In addition, extremely small temperature differences define the boundary line between rain and snow.

+Will the approaching storm bring heavy snowfall to your area?

Each winter, NWS meteorologists issue winter weather warnings and forecasts and monitor weather data from across the nation for developing areas of heavy snow and freezing precipitation. NCEP's Weather Prediction Center (WPC) and the NWS Weather Forecast Office (WFO) in your area provide critical guidance, warnings and forecasts for the protection of life and property. The NWS Storm Prediction Center provides smaller, more targeted information for rapidly approaching intense, heavy winter precipitation. NWS provides this information to the public, private sector meteorologists and state and local governments. For additional information on whether your area is going to be impacted by heavy snow or other winter weather, visit the WPC's Winter Weather Forecasts or

+Are you prepared for winter weather?

Winter weather too often catches people unprepared. Researchers say that 70 percent of the fatalities related to ice and snow occur in automobiles, and about 25 percent of all winter related fatalities are people that are caught off guard, out in the storm. What winter weather preparations are being made in your area, and what are the appropriate steps to take that will ensure your winter weather safety? Help your readers, viewers and listeners make sure their homes and cars are ready for the worst winter has to offer.

+Getting the latest winter weather information

A great way to keep ahead of a winter storm is with NOAA Weather Radio (NWR), a small receiver device that can be purchased at many electronic stores. As the "Voice of the National Weather Service," it provides continuous broadcasts of the latest weather information from local National Weather Service offices. The NWR network has more than 425 stations, covering all 50 states, adjacent coastal waters, Puerto Rico, the U.S. Virgin Islands, and U.S. Pacific Territories. Weather radios come in many sizes, with a variety of functions and costs. The NWR network has been further advanced by the implementation of Specific Area Message Encoding (SAME) technology. The SAME allows the user to receive warnings only for their specific location. SAME receivers are a live-saving tool, providing audible alert tones for any weather warnings. A NOAA Weather Radio is a useful and potentially life-saving gift idea this holiday season.

+What is wind chill?

One of the gravest dangers of winter weather is wind chill. The wind chill is based on the rate of heat loss from exposed skin by combined effects of wind and cold. As the wind increases, heat is carried away from the body at an accelerated rate, driving down the body temperature. Animals are also effected by wind chill. Check out the wind chill chart.

+NOAA's Snow and Ice Center

The National Snow and Ice Data Center (NSIDC) serves as the national information center that supports research in glaciers and freezing weather phenomenon. The NSIDC archives snow and ice data, and maintains information about everything from avalanches to icebergs. The NSIDC web site contains a fascinating list of Questions and Answers about snow that are sure to be of interest to anyone experiencing winter weather.

+Hard at work when the storm hits

While most of us stay home from work or school during severe winter weather, National Weather Service meteorologists are hard at work. Twenty-four hours a day, 365 days a year, NWS meteorologists staff local offices across the country to make sure the latest forecasts, watches and warnings get out to emergency managers, the media, and the public. What's it like at a forecast office? Don't wait for a major winter storm; contact your local office and ask to spend the day with them, and observe the exciting, day-to-day process of forecasting the snow before it hits.

+La Nina and the North Atlantic Oscillation

La Niña

La Niña refers to a period when ocean temperatures across the central and eastern tropical Pacific Ocean are cooler than normal. The cooling of the ocean waters leads to changes in the patterns of tropical rainfall from Indonesia to South American, a distance of more than one-half the circumference of the earth, which significantly affects the strength and location of the atmospheric jet stream over the eastern North Pacific and North America. These changes in the jet stream alter U.S. weather patterns.

La Niña patterns can be categorized according to the combined strength, location and coverage of the cold ocean waters. Moderate-to-strong La Niña systems impact the weather patterns in a similar manner, and thus this distinction is thought by many to have little meaning. The weather patterns with a weak La Niña tend to be somewhere in between those of a stronger episode and those of near-neutral conditions.

North Atlantic Oscillation

Naturally occurring global-scale circulation patterns are a prominent aspect of our climate and that are independent of the La Niña influence. The North Atlantic Oscillation (NAO) is one such wild card. The NAO reflects large-scale changes in the portion of the jet stream which extends from the eastern United States. to Europe. It NAO exhibits an enormous degree of variability because it can persist for years in a particular state and than transition to a completely different phase the next winter. The NAO can also vary substantially within a given year. This variability, as well as the El Niño-La Niña cycle, are major contributors to the differences in weather patterns from one winter to the next and to the variability in weather within a given winter season. Scientists have not yet identified a clear climate signal that will give us a meaningful hint as to the state of the NAO during an upcoming winter.

The NAO has affected the La Niña signal in the past. Two recent examples for the eastern United States are the cold and snowy 1995/96 La Niña winter compared with the very mild 1998/99 winter. Opposite phases of the NAO during these two winters were a major contributing factor to these differences. Therefore, exercise caution when comparison of one La Niña to the next.