The National Weather Service (NWS) issues a variety of products to keep viewers informed of unusual, inconvenient and hazardous weather conditions. A multi-tier concept is employed to accomplish this task with Outlooks, Watches, Warnings and Advisories to point out specific conditions.
Outlook - Used to give considerable lead time that a hazardous event may develop.
Watch - Issued when the risk of a hazardous weather or hydrologic event has increased significantly, but its occurrence, location, and/or timing is still uncertain. It is intended to provide enough lead time so those who need to set their plans in motion can do so.
Warning - Issued when a hazardous event is occurring or has a very high probability of occurrence. Warnings advise of a threat to life or property.
Advisory - Issued when a hazardous event is occurring or has a very high probability of occurrence. Advisories describe events that cause significant inconvenience.
Spring/Summer Weather Terms
Severe Thunderstorm Watch - Conditions are favorable for thunderstorms to produce large hail or damaging winds. These watches are normally issued for four to six hours at a time, and for a large number of counties.
Severe Thunderstorm Warning - Issued when a thunderstorm is occurring or imminent that contains winds of at least 58 mph, and/or hail of at least 3/4" in diameter.
Tornado Watch - Conditions are favorable for tornadoes to develop. It is normally issued for four to six hours, and can include many counties. If you are in or near the Tornado Watch area, stay informed with NOAA Weather Radio, commercial radio, or television.
Tornado Warning - Issued when a tornado is occurring (and has been seen by trained storm spotters), or is developing (and has been seen by radar).
Severe Weather Statement - The Severe Weather Statement is a follow-up to Tornado and Severe Thunderstorm Warnings. These statements inform you of the current status of a tornado or severe thunderstorm. In addition, it gives the history of a storm, where it is moving, and who it will affect. This NWS product is also used to cancel or expire a warning.
Hazardous Weather Outlook - A product issued by the NWS to discuss the significant weather of the day, or possibly next two days. The Hazardous Weather Outlook will detail the type of severe weather expected (if any), timing, and expected location of the severe weather.
Flash Flood Watch - This is issued when heavy rain may develop and result in flash flooding in or near the watch area. A Flash Flood Watch will also be issued if ground, river/stream conditions, or radar surveillance indicate flash flooding is possible, but not imminent within a designated area.
Flash Flood Warning - A flood warning issued for life/property threatening flooding that will occur within 6 hours. It could be issued for rural or urban areas as well as for areas along the major rivers.
Flash Flood Statement - Flash Flood Statements are used to continue Flash Flood Watches, to follow-up watches and warnings with additional or current information, and to keep you informed of the flooding status.
Urban/Small Stream Flood Advisory - Issued when heavy rain will cause flooding of streets and low-lying places in urban areas. Also used if small rural or urban streams are expected to reach or exceed bankfull.
Fall/Winter Weather Terms
Winter Weather Advisory - Issued for non life-threatening (if caution is exercised) events such as: 3" or more of snowfall, a significant mix of freezing and frozen precipitation, blowing snow which intermittently reduces visibility to less than 1/4 mile, drifting snow which closes roadways, sleet accumulations of 1/2" or more, freezing rain or drizzle with less than 1/4" accumulation.
Winter Storm Watch - Issued when conditions are favorable for the development of hazardous weather elements such as heavy snow and/or blizzard conditions, or significant accumulations of freezing rain or sleet. Watches are usually issued 24 to 48 hours in advance of the event.
Winter Storm Warning - Issued for more serious winter weather events such as: 6" or more of snowfall in 12 hours or 8" or more in 24 hours, a mix of freezing and frozen precipitation which causes life-threatening conditions, 3 to 5 inches of snow combined with high winds (20 mph or more).
Blizzard Warning - Issued for winter storms with sustained winds or frequent gusts to 35 miles per hour or greater and considerable falling and/or blowing snow reducing visibility to less than 1/4 mile.
Ice Storm Warning - Issued when damaging accumulations of ice are expected during freezing rain situations, with walking and driving becoming extremely dangerous. Significant ice accumulations are usually 1/4 inch or greater which may cause power lines and large tree branches to break.
Sleet Warning - Issued when accumulations of sleet, to a depth of 1/2 inch or more, are expected. This is a relatively rare event.
Wind Chill Warning - Issued when wind chills of -35F or lower are expected with winds of at least 10 mph or greater.
High Wind Warning - Issued when sustained winds are forecast to be at least 40 mph or more for 1 hour or more, or gusts of 58 mph or more.
High Wind Watch - Issued 12-36 hours in advance of non-convective sustained winds of 40 mph and gusts 58 mph or stronger.
Wind Advisory - Issued when sustained winds are forecast to be at least 30 mph for 1 hour or more, or gusts between 45 and 57 mph.
Freeze Warning - Used during the growing season when temperatures are expected to drop well below freezing over a large area, regardless of whether frost forms or not.
Freeze Advisory - Issued during the growing season when temperatures are forecast to be less than 30 degrees.
Frost Advisories - Issued during the growing season when temperatures of between 33 and 39 degrees are expected.
Heat Advisory - Issued when heat indeces of between 105 and 114 degrees are expected during the day or heat indeces of 80 degrees or more are expected during the night.
Fog Advisory - Used when dense fog covers a significant area and reduces visibility to less than 1/4 mile. May be called a Dense Fog Advisory.
This and more information can be found at the National Oceanic and Atmospheric Administration Web site at www.noaa.gov