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NWS St. Louis Decision Support Workshop Watch, Warning, and Advisory Products and Criteria

NWS St. Louis Decision Support Workshop Watch, Warning, and Advisory Products and Criteria. Winter Weather. Watch: Issued 24 – 36 hours in advance when warning criteria is expected to be met Warning: Life threatening conditions Advisory: Inconvenience. Winter Weather: Warning.

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NWS St. Louis Decision Support Workshop Watch, Warning, and Advisory Products and Criteria

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  1. NWS St. LouisDecision Support WorkshopWatch, Warning, and Advisory Products and Criteria

  2. Winter Weather • Watch: Issued 24 – 36 hours in advance when warning criteria is expected to be met • Warning: Life threatening conditions • Advisory: Inconvenience

  3. Winter Weather: Warning • Blizzard Warning: For 3 hours or more • Sustained wind or frequent gusts of 35 mph or greater • Snow or blowing snow reducing visibility to ¼ mile or less

  4. Winter Weather: Warning • Ice Storm Warning • Ice accumulation due to freezing rain of ¼ inch or greater

  5. Winter Weather: Warning • Winter Storm Warning • 6 inches or more of snow • ½ inch or more of sleet • or a combination of winter precipitation such that the forecaster feels it will create life threatening conditions

  6. Winter Weather: Warning • Wind Chill Warning • Wind chill values -25 F or colder

  7. Winter Weather: Advisory • Freezing Rain Advisory • Ice accumulation due to freezing rain or drizzle of less than ¼ inch

  8. Winter Weather: Advisory • Winter Weather Advisory • Snow of 3 – 5 inches • Combination of winter precipitation types: light amounts • Forecaster discretion

  9. Winter Weather: Advisory • Wind Chill Advisory: • Wind chill values -15 to -24 F

  10. Severe Weather • Hazardous Weather Outlook • Quick summary of hazardous weather expected for the next 7 days • Day 1 • Day 2 - 7

  11. Severe Weather • Severe thunderstorm outlooks: Storm Prediction Center (SPC) • Day 1, Day 2, Day 3, Day 4 – 8 • Slight, Moderate, High • The probability values represent the chance of severe weather within 25 miles of any point in the area. Even a 10% chance of a tornado within 25 miles of a point means a much bigger threat than usual, and should be taken seriously.

  12. Severe Weather

  13. Severe Weather • Severe Thunderstorm/Tornado Watch • Organized episode of severe weather • Issued for 3 – 8 hours • Typically cover 25,000 square miles • Collaborated with local office

  14. Severe Weather • Tornado warning • Radar signature of circulation or spotter reports • Severe thunderstorm warning • Radar signature or spotter reports • 1 inch or larger hail • Wind gusts 50 Knots (58 mph)

  15. Flash Flood/Flood • Watch: excessive rainfall expected over the given period that may cause flooding • Flash Flood: Rapid rise of water causing inundation of normally dry areas over a period of 6 hours or less • Flood: Rise of water due to rainfall over a longer period. Flooding takes more than 6 hours to develop

  16. Excessive Heat • Watch • Excessive heat condition expected within 24 – 48 hours

  17. Excessive Heat • Advisory • Maximum Heat Index (HI) of 105 F • Maximum HI of 100 F – 104 F for 4 days • Warning • Maximum Heat Index of 110 F for 2 days • Advisory criteria met for 4 or more days • City of St. Louis: 2 days

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