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NYC Hazards: Winter Weather Terms

Snow on trees
 
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Storms

  • WINTER STORM OUTLOOK: Issued prior to a Winter Storm Watch, the outlook is given when forecasters believe winter storm conditions are possible. A Winter Storm Outlook is usually issued 3 to 5 days in advance of a winter storm.
  • WINTER STORM WATCH: Issued by the local NWS Forecast Office, the Winter Storm Watch alerts the public to the possibility of severe winter conditions (i.e., heavy snow or significant ice accumulations), usually at least 24 to 36 hours in advance. The criteria for this watch can vary from place to place.
  • WINTER STORM WARNING: Issued by the local NWS Forecast Office when hazardous winter weather in the form of heavy snow, heavy freezing rain, or heavy sleet is imminent or occurring. Winter Storm Warnings are usually issued 12 to 24 hours before the event is expected to begin, but the criteria for this warning can vary from place to place. A winter storm warning may also be issued for heavy snow combined with strong winds of 25-34 mph that will cause blowing and drifting of the snow. A warning may still be warranted if the event is expected to exceed advisory criteria, but fall just short of warning criteria and will significantly impact mass transit and/or utilities.
  • WINTER WEATHER ADVISORY: Issued by the local NWS Forecast Office when a low pressure system produces a combination of winter weather conditions (i.e., snow, freezing rain, sleet, etc.) that present a hazard, but does not meet warning criteria. These winter conditions will cause significant inconvenience and may be hazardous. If caution is exercised, these situations should not become life-threatening. The greatest hazard is often to motorists.
  • BLIZZARD WATCH: Issued by the National Weather Service when sustained winds of at least 35 mph, and falling or blowing snow create visibilities at or below ¼ mile (these conditions should persist for at least three hours), are possible within 24 to 36 hours.
  • BLIZZARD WARNING: Issued by the National Weather Service when sustained winds of at least 35 mph, and falling or blowing snow create visibilities at or below ¼ mile (these conditions should persist for at least three hours), are expected within 16 hours.
  • ICE STORM WARNING: Issued by the National Weather Service when a heavy accumulation of ice (at least ¼ inch thick) is forecast to accrete and down trees and power lines, resulting in significant and widespread power outages.

Freezing Rain & Snow

  • FREEZING RAIN ADVISORY: Issued by the National Weather Service when freezing rain or drizzle is forecast but a significant accumulation is not expected. However, even small amounts of freezing rain or freezing drizzle may cause driving and walking on untreated surfaces treacherous.
  • BLOWING SNOW ADVISORY: Issued by the National Weather Service when wind-driven snow is expected to reduce surface visibility. Blowing snow may be falling snow, or snow that has already accumulated but is picked up and blown by strong winds. Visibility conditions are not expected to deteriorate sufficiently to issue a Blizzard Warning. Blowing snow is usually accompanied by drifting snow.
  • SNOW ADVISORY: Issued by the National Weather Service when a low pressure system produces snow that may cause significant inconveniences, but do not meet warning criteria. An average snowfall of 3 inches is expected. Amounts can range from 2 to 5 inches. A Snow Advisory may also be issued for snowfalls under two inches at the beginning of the snow season or after a prolonged period between snowfall events.
  • HEAVY SNOW WATCH: Issued by the National Weather Service when an average snowfall of 6 inches in 12 hours or 8 inches in 24 hours is expected.
  • HEAVY SNOW WARNING: Issued by the National Weather Service when snowfall totaling six inches or more in 12 hours or less is strongly expected or imminent. Also is issued when snowfall totaling eight inches or more in 24 hours is strongly expected or imminent.

Wind Chill

  • WIND CHILL ADVISORY: Issued by the National Weather Service when potentially dangerous wind chill readings are expected (-15°F to -24°F). This advisory indicates that wind chill temperatures are expected to be a significant inconvenience to life with prolonged exposure, and, if caution is not exercised, could lead to hazardous consequences.
  • WIND CHILL WATCH: Issued by the National Weather Service when life-threatening wind chill readings could reach dangerous levels within the next 12 to 48 hours.
  • WIND CHILL WARNING: Issued by the National Weather Service when life-threatening wind chill readings are expected to be hazardous to life within several minutes of exposure (-25°F or colder).

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