Winter Weather Resources and Frequently Asked Questions

Have you ever wondered how the National Weather Service can tell a major winter storm is brewing and will impact your area in the coming days or hours? How can meteorologists tell if a storm is intensifying and where it will bring the most snow? It's a highly sophisticated process. It all starts with observing the current situation. The National Weather Service operates a widespread network of observing systems such as geostationary satellites, Doppler radars, and automated surface observing systems that constantly monitor the current weather conditions. State-of-the-art numerical computer models then provide a glimpse of what will happen in the next hours to days. The models are analyzed by NWS meteorologists who use their experience and expertise to write and send forecasts.

 

• 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: A warning is issued for a significant winter weather event including snow, ice, sleet, or blowing snow, or a combination of these hazards. Travel will become difficult or impossible in some situations. Delay your travel plans until conditions improve.
• 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: Issued when snow and strong winds will combine to produce a blinding snow (near zero visibility), deep drifts, and life-threatening wind chill. Be sure to listen carefully to weather reports and NOAA Weather Radio for the latest winter storm watches, warnings, and advisories.

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.
 

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 weather.gov.
 

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 outside during a 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? Make sure your home and car are ready for the worst winter has to offer.
 

A great way to keep ahead of a winter storm is with NOAA Weather Radio (NWR), a specialized radio receiver that can be purchased at many retail outlets. 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 1000 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 and price points, with a variety of functions, including visual alert signals like flashing lights. The NWR network has been further advanced by the implementation of Specific Area Message Encoding (SAME) technology. SAME allows the user to receive warnings only for their specific location. SAME receivers are a life-saving tool, providing audible alert tones for any weather warnings.

 

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 due to the 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 affected by wind chill. Check out the wind chill chart for more information.
 

The National Snow and Ice Data Center (NSIDC) serves as the national information center that supports research in glaciers and freezing weather phenomena. 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 Quick Facts about snow that are sure to be of interest to anyone experiencing winter weather.

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 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 America, 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

Global-scale circulation patterns are a natural part of our climate and occur 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. The NAO exhibits an enormous degree of variability because it can persist for years in a particular state and then transition to a completely different phase the next winter. It 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. In the eastern United States, the cold and snowy 1995/96 winter and the very mild 1998/99 winter were both La Niña winters. However, the opposite phases of the NAO during these two winters contributed significantly to the difference between them. Therefore, exercise caution when comparing one La Niña to the next.