Severe Weather Alert Guide

It is very important to understand the difference between a weather WATCH and WARNING.  The term WATCH implies that people should be alert for the possibility of severe weather , or flash flooding, and have a plan of action in case a storm threatens. When a WARNING is issued by the National Weather Service, this means that a tornado, severe thunderstorm, or flood has been detected by radar or observed by trained storm spotters (SKYWARN). 

Warnings are for short-fuse events that only last an hour or so. People in the path of the storm are expected to take action to protect life and property when the term WARNING is heard. Following is a list of watches/warnings/advisories that the National Weather Services (NWS) issues and the criteria used for issuing them:   

WIND ALERTS 

  Warning Advisory Watch
Hurricane Force Wind
Sustained winds or frequent gusts of 74 mph or greater not directly associated with a hurricane are either predicted or occurring.
 
Sustained winds or frequent gusts of 74 mph or greater not directly associated with a hurricane are possible.
High Wind
High winds (not related to thunderstorms) that may be hazardous or life threatening are occurring or highly likely.  The wind speed threshold varies depending upon location.
 
High winds (not related to thunderstorms) that may be hazardous or life threatening are possible.  The wind speed threshold varies depending upon location.
Lake Wind
 
Strong winds causing rough conditions on lakes that may capsize small boats
 
Wind
 
Sustained winds of 25 to 39 mph and/or gust to 57 mph are occurring or highly likely.
 

For more severe weather information, visit http://www.weather.gov 

STORM/TORNADO ALERTS 

  Warning Advisory Watch
Tornado
Tornado is indicated by radar or has been sighted.
 
Conditions are favorable for tornadoes in and close to the watch area.
Severe Thunderstorm
A severe thunderstorm is indicated by radar or spotters report hail 1 inch diameter or larger and/or winds 58 mph or greater.
 
Conditions are favorable for severe thunderstorms with hail 1 inch diameter or larger and/or winds 58 mph or greater in and close to the watch area.

For more severe weather information, visit http://www.weather.gov 

FLOOD ALERTS 

  Warning Advisory Watch
Flash Flood                   
Flash flooding is in progress or highly likely. Flash floods differ from other floods in that rapid flows of water into a normally dry area or rapid rises in water levels begin within a short time after the event that causes the flooding.
 
Weather and hydrologic conditions are favorable for flash flooding in and close to the watch area.  Flash floods differ from other floods in that rapid flows of water into a normally dry area or rapid rises in water levels begin within a short time after the event that causes the flooding.
Coastal Flood 
Coastal flooding posing a serious threat to life and property is occurring or highly likely.
 
Coastal flooding with significant impacts is possible.
Lakeshore Flood
Lakeshore and connecting waterway flooding posing a serious threat to life and property is occurring or highly likely.
 
Lakeshore and connecting waterway flooding with significant impacts is possible.
Flood (River Flood)
Flooding along rivers and larger streams with a serious threat to life or property is either occurring or imminent.
 
Weather and river conditions indicate flooding along rivers and larger streams is possible but not occurring or imminent.
Area Flood
Flooding over areas, small streams or areas with a serious threat to life or property is either occurring or imminent.
Flooding over areas, small streams or areas is occurring or imminent. It is not expected to cause a serious threat to life or property.
Weather and hydrologic conditions indicate flooding with serious impacts is possible in and close to the watch area

For more severe weather information, visit http://www.weather.gov 

WINTER ALERTS 

  Warning Advisory Watch
Blizzard
Sustained or frequent winds of 35 mph or higher with falling and/or blowing snow that frequently reduces visibility to ¼ of a mile or less is occurring or highly likely. These conditions last for a minimum of 3 hours.
 
Sustained or frequent winds of 35 mph or higher with falling and/or blowing snow that frequently reduces visibility to ¼ of a mile or less is possible. These conditions last for a minimum of 3 hours.
Ice Storm
Freezing rain producing significant, possibly damaging accumulations of ice is occurring or highly likely. Typically issued any time more than ¼” of ice accumulation is expected but threshold varies depending on location.
 
 
Winter Storm
Winter storm producing heavy snow, sleet or ice accumulations or a combination of dangerous winter weather elements is occurring or highly likely. The threshold for accumulations that constitute “Heavy” can vary depending on location.
 
Winter storm with heavy snow, sleet or ice accumulations or a combination of dangerous winter weather elements is possible.The threshold for accumulations that constitute “Heavy” can vary depending on location.
Lake Effect Snow
Lake effect snowfall that may be hazardous or life threatening is occurring or highly likely.
Lake effect snowfall is occurring or highly likely and could be dangerous if appropriate action is not taken.
Lake effect snowfall that may be hazardous or life threatening is possible.
Wind Chill
Life-threatening wind chill values are occurring or highly likely.
Wind chills are occurring or highly likely that could be dangerous if appropriate action is not taken.
Life-threatening wind chill values are possible.
Freezing Rain
 
Freezing rain or freezing drizzle is occurring or highly likely but significant accumulation is not expected. Even small amounts of freezing rain or freezing drizzle can cause dangerous travel conditions.
 
Winter Weather
 
Snow, blowing snow, freezing rain, freezing drizzle, sleet or a combination of elements present a hazard but are not significant enough to meet warning thresholds.
 
Hard Freeze
Issued during growing season when temperatures are likely to drop below freezing long enough to kill vegetation and freeze the ground solid.
 
Issued during growing season when temperatures dropping below freezing long enough to kill vegetation and freeze the ground solid are possible.
Freeze
Issued during growing season when temperatures are likely to drop below freezing over a large area for an extended period of time.
Issued during the growing season when widespread frost is likely over an extensive area.
Issued during growing season when temperatures below freezing over a large area for an extended period of time are possible.

For more severe weather information, visit http://www.weather.gov.

VISIBILITY ALERTS 

  Warning Advisory Watch
Dust Storm
Dust storm with visibility generally ¼ mile or less and winds of 30mph or more is occurring or imminent. Thresholds vary depending on region.
 
 
Dense Fog
 
Issued when fog with visibilities of 1/8 mile or less is occurring or highly likely.
 
Blowing Dust
 
Visibilities less than 1 mile but greater than ¼ mile due to blowing dust. Visibility thresholds vary depending on region.
 

For more severe weather information, visit http://www.weather.gov 

MARINE ALERTS 

  Warning Advisory Watch
Storm
Sustained surface winds not associated with a tropical cyclone between 48 knots (55 mph) and 63 knots (73 mph) are occurring or predicted.
 
 
Tsunami
Warnings are issued due to the imminent threat of a tsunami from a large undersea earthquake or following confirmation that a potentially destructive tsunami is underway.
 
Watches are issued based on seismic information without confirmation that a destructive tsunami is underway.
Gale
Sustained winds (not directly associated with a tropical cyclone) of 34 to 47 knots (39 to 54 mph) are occurring or highly likely.
 
Sustained winds (not directly associated with a tropical cyclone) of 34 to 47 knots (39 to 54 mph) are occurring or possible.
Marine
Short-term (up to 2 hours) hazardous weather conditions with wind gusts of 34 knots (39 mph) or greater and/or hail ¾” or greater and/or waterspouts.  
 
 
High Surf
Breaking wave action results in an especially heightened threat to life and property within the surf zone. High surf criteria vary by region.
Breaking wave action results in heightened threat to life and property within the surf zone. High surf criteria vary by region.
 
Small Craft
 
Conditions may be hazardous for small craft due to winds, waves or rough bars found near harbor or river entrances.  Thresholds vary by region.
 

For more marine weather information, visit http://www.weather.gov/om/marine/home.htm

TROPICAL ALERTS 

  Warning Advisory Watch
Hurricane
Sustained winds of 74 mph (64 knots) or higher associated with a hurricane are likely in a coastal area within 24 hours. May continue in effect when dangerously high water/waves linger even though winds may be less than hurricane force.
 
Sustained winds of 74 mph (64 knots) or higher associated with a hurricane are possible in a coastal area generally within 36 hours.
Typhoon
Sustained winds of 74 mph or higher associated with a typhoon are likely in a coastal area within 24 hours. May continue in effect when dangerously high water/waves linger even though winds may be less than typhoon force.
 
Sustained winds of 74 mph or higher associated with a typhoon are possible in a coastal area generally within 36 hours.
Inland Hurricane
Issued for interior counties for sustained winds of 74 mph or greater associated with a hurricane.  Those winds are likely within 24 hours.
 
Issued for interior counties for sustained winds of 74 mph or greater associated with a hurricane. Those winds are possible within 36 hours.
Tropical Storm
Sustained winds of 39 to 73 mph (34 to 63 knots) associated with a tropical storm are likely in a coastal location within 24 hours.
 
Sustained winds of 39 to 73 mph (34 to 63 knots) associated with a tropical storm are possible in a coastal location generally within 36 hours.
Inland Tropical Storm
Issued for interior counties when sustained winds of 39 to 73 mph or greater associated with a tropical storm are likely in 24 hours.
 
Issued for interior counties when sustained winds of 39 to 73 mph or greater associated with a tropical storm are possible in 36 hours.

For more tropical weather information, visit www.nhc.noaa.gov

ADDITIONAL ALERTS 

  Warning Advisory Watch
Excessive Heat
High heat index values are occurring or highly likely.
 
High heat index values are possible.
Heat
 
Heat index values are high enough to present a hazard if proper caution is not taken.
 
Fire Weather
(Red Flag Warning)
Weather conditions conducive to rapid growth and spread of wildfires are occurring or highly likely.
 
Weather conditions conducive to rapid growth and spread of wildfires are possible.

For more severe weather information, visit http://www.weather.gov