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 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

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

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

Winter Weather: Warning Wind Chill Warning – Wind chill values -25 F or colder

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

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

Winter Weather: Advisory Wind Chill Advisory: – Wind chill values -15 to -24 F

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

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.

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

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)

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

Excessive Heat Watch – Excessive heat condition expected within 24 – 48 hours

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