Watches and Warnings

How the National Weather Service Issues Watches. Warnings, and Advisories

Local forecast offices, like the National Weather Service in Milwaukee/Sullivan, issue all watches, warnings, and advisories except Severe Thunderstorm and Tornado Watches. The Storm Prediction Center in Norman, OK issues the severe thunderstorm and tornado watches. The NWS uses a program called WarnGen, which takes the information that the meteorologists put in and provides its own text from the information. So if you thought that warnings looked generic, you were in fact correct.

First, a meteorologist who is forecasting a thunderstorm must find a thunderstorm cell on their radar system that meets the criteria for a warning. Next, he or she clicks on the cell and the computer computes the direction of the thunderstorm, how fast it is going, and when it will affect certain cities. It also computes which counties to warn. Once a cell meeting warning criteria is found, the meteorologist must switch over to another part of the program where he or she can select different phrases and the type of warning to put into the text product. The computer then takes the information and creates a text product. Finally, the meteorologist can view the text product and send it to various locations.

Types of Warnings and Watches that could possibly impact Wisconsin

  1. Severe Thunderstorm

    2. Watch – Issued for a specific area where storms are likely to develop and become severe.

    Warning – Issued for a specific county when a severe thunderstorm has been sighted or indicated by radar. Requirements include winds of 58-mph or more and/or hail ¾ of an inch in diameter or larger.

  2. Tornado

    3. Watch – Issued for a specific area where storms are likely to develop and produce tornadoes.

    Warning – Issued for a specific county when a tornado has been sighted or indicated by radar.

  3. Small Craft Advisory

    4. Alerts mariners to weather or sea conditions exceeding 2 hours, either present or forecast, that is potentially hazardous to small craft (canoes, paddleboats, etc.). Hazardous conditions include winds 18 – 34 knots and/or dangerous wave conditions. It is up to the mariner then to make the decision.

  4. Gale Warning

    5. Indicates winds 34 – 47 knots are forecast for the area. This is not associated with any kind of tropical disturbance.

  5. Storm Warning

    6. Indicates winds 48 knots or higher are forecast for the area. This is not associated with any kind of tropical disturbance.

  6. Special Marine Warning

    7. Indicates potentially hazardous weather conditions 2 hours or less and producing wind speeds of 34 knots or more not covered by existing marine warnings.

  7. Flood

    8. Watch – Issued for a specific area if flooding is possible.

    Warning – Issued for a specific area when a flood has been reported or is imminent.

  8. Flash Flood

    9. Watch – Issued for a specific area if flash flooding is possible shortly after rain event.

    Warning – Issued for a specific area when a flash flood has been reported or is imminent shortly after rain event.

    *Flash flooding occurs more quickly and suddenly than flooding

  9. Urban/Small Stream Advisory

    10. Small streams, streets or low-lying areas are flooding

  10. Winter Storm

    11. Watch – Issued if there is a threat for heavy snow or sleet, significant accumulations of freezing rain or freezing drizzle, or any combination of these. Issued for the second and third periods of a forecast, i.e. 12 to 36 hours in advance of the event. Generally not issued for the fourth period of a forecast. The definition of heavy snow in Kentucky is 4" or more in 12 hours, or 6" or more in 24 hours.

    Warning – Issued if there is a high probability that severe winter weather will occur, such as heavy snow or sleet, significant accumulations of freezing rain or freezing drizzle, or any combination of these. Issued normally for the first period forecast, i.e. less than or equal to 12 hours in advance of the event. A winter storm warning may be extended into the second period of the forecast if necessary.

  11. Winter Weather Advisory

    12. Used when a mixture of precipitation such as snow, sleet, and freezing rain or drizzle is expected, but will not reach warning criteria. If only freezing rain or freezing drizzle is expected, then the product would be issued as a Freezing Rain or Freezing Drizzle advisory.

     

     

  12. Blizzard Warning

    13. Issued for winter storms with sustained winds or frequent gusts of 35 mph or greater, and considerable falling and/or blowing snow reducing visibilities to 1/4 mile or less. These conditions should last for 3 hours or longer.
  13. Snow Advisory

    14. Used when snowfall amounts are below warning criteria, but nonetheless pose a hazard to the public. Issued for average snowfall amounts of less than 4". Forecast amounts would be 1-2", 1-3", 2-4", or around 3".

  14. Wind Chill Advisory

    15. Issued when wind chill temperatures are expected to reach -20°F to -35°F, with a minimum wind speed of about 10-mph.
  15. Heavy Snow Warning

    16. Issued when heavy snowfall is expected and will be accompanied by moderate or heavy snowfall rates.

  16. Wind Chill Warning

Issued when wind chill temperatures are expected to reach -35°F or colder, with a minimum wind speed of about 10-mph.