| Warnings | A warning is issued when hazardous weather is occuring, immenent or likely to occur. A warning means weather conditions pose a threat to life or property. People in the path of the storm need to take protective action. NWS may activate weather spotters in areas effected by warnings to help them better track and analyze the event. |
| Blizzard Warning | Sustained winds or frequent gusts of 35 mph (56 km/h) or greater, considerable falling and/or blowing snow reducing visibility frequently to 1/4 mile (0.4 km) or less for a period of three hours or more. There are no temperature criteria in the definition of a blizzard but freezing temperatures and 35 mph winds will create sub-zero wind chills. |
| Excessive heat warning | Extreme heat index making it feel like above 110 °F (43 °C) with a minimum above 80 °F (27 °C). |
| Flash Flood Warning | Signifies a dangerous situation where rapid flooding of small rivers, streams, creaks, or urban areas are imminent or already occurring. Very heavy rain that falls in a short time period can lead to flash flooding, depending on local terrain, ground cover, degree of urbanization, degree of man-made changes to river banks, and initial ground or river |
| Heavy sleet warning | Accumulations of 1/2 inch (12 mm) or more of sleet. |
| Heavy Snow Warning | Snowfall of 6 inches (15 cm) or more in 12 hours or less, or 8 inches (20 cm) or more in 24 hours or less. |
| High wind warning | Sustained winds of 40 mph (65 km/h) or greater for a duration of one hour or longer or gusts to 58 mph (93 km/h) or greater. |
| Ice Storm Warning | Accumulations of 1/4 inch (6mm) or more of freezing rain |
| Severe Thunderstorm Warning | Issued when a thunderstorm produces hail 3/4 inch (20 mm) or larger in diameter and/or winds which equal or exceed 58 mph (93 km/h). Severe thunderstorms can result in the loss of life and/or property. Information in this warning includes: where the storm is, what towns will be affected, and the primary threat associated with the storm. |
| Tornado Warning | Tornado is indicated by radar or sighted by storm spotters. The warning will include where the tornado is and what towns will be in its path. (Also automatically indicates a Severe Thunderstorm Warning) |
| Wind chill warning | Extreme wind chills making it feel like -30 °F (-34 °C) or colder. |
| Winter Storm Warning | Hazardous winter weather conditions that pose a threat to life and/or property are occurring, imminent or likely. The generic term, winter storm warning, is used for a combination of two or more of the following winter weather events; heavy snow, freezing rain, sleet and strong winds. |
| Severe Weather Statement | Issued when the forecaster wants to follow up a warning with important information on the progress of severe weather elements. |
| Watches | A watch is used when the risk of a hazardous weather has increased significantly, but its occurrence, location 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. A watch means that hazardous weather is possible. People should have a plan of action in case a storm threatens and they should listen for later information and possible warnings especially when planning travel or outdoor activities. NWS may activate weather spotters in areas effected by watches to help them better track and analyze the event. |
| Flash Flood Watch | Indicates that flash flooding is possible in and close to the watch area. Those in the affected area are urged to be ready to take quick action if a flash flood warning is issued or flooding is observed. |
| Severe Thunderstorm Watch | Conditions are favorable for the development of severe thunderstorms in and close to the watch area. Watches are usually in effect for several hours, with 6 hours being the most common. |
| Tornado Watch | Conditions are favorable for the development of severe thunderstorms producing tornadoes in and close to the watch area. Watches are usually in effect for several hours, with 6 hours being the most common. (Also automatically indicates a Severe Thunderstorm Watch) |
| Winter Storm Watch | Conditions are favorable for hazardous winter weather conditions including heavy snow, blizzard conditions, or significant accumulations of freezing rain or sleet. These watches are issued by the Weather Service Forecast Office and are usually issued 12 to 36 hours in advance of the event. |
| Advisories | An advisory is issued when hazardous weather is occurring, imminent or likely to occur. Advisories are for less serious conditions than warnings, that cause significant inconvenience and if caution is not exercised, could lead to situations that may threaten life or property. NWS may activate weather spotters in areas effected by advisories to help them better track and analyze the event. |
| Freezing rain advisory | Accumulations of less than 1/4 inch (6 mm) of freezing rain or freezing drizzle |
| Heat advisory | Maximum heat index of 105 to 110 °F (40 to 43 °C) with a minimum of 75 °F (24 °C) for two or more consecutive days. |
| Sleet advisory | For accumulations of less than 1/2 inch (12 mm) of sleet |
| Snow advisory | Snowfall of 3 to 5 inches (8 to 14 cm). |
| Snow and blowing snow advisory | Sustained winds or frequent gusts of 25 to 35 mph (40 to 56 km/h) accompanied by falling and blowing snow, occasionally reducing visibility to 1/4 mile (0.4 km) or less. |
| Wind chill advisory | Dangerous wind chills making it feel like -20 °F (-28 °C) to -30 °F (-34 °C). |
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Beaufort wind scale and other wind terms
Beaufort
wind scale
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Cold air funnel - A funnel cloud
or (rarely) a small relatively weak
tornado that can develop from a small
shower or thunderstorm when the air
aloft is unusually cold. They are much
less violent than other types of
tornadoes. Crest - The highest level of a flood wave as it passes a point. Degree Day - Gauges the amount of heating or cooling needed for a building using 65 °F as a baseline. To compute degree days, the average temperature for a day is taken and referenced to 65 °F. An average temperature of 50 °F yields 15 heating degree days, while an average temperature of 75 °F would yield 10 cooling degree days. Dew Point - A measure of atmospheric moisture. It is the temperature to which air must be cooled in order to reach saturation (assuming pressure and moisture content are constant). Doppler Radar - Radar that can measure radial velocity, the instantaneous component of motion parallel to the radar beam (i.e., toward or away from the radar). Downburst - A strong downdraft from a thunderstorm resulting in an outward burst of damaging winds on or near the ground. Downburst winds are often 50 to 100 mph (80 to 160 km/h) and in a few cases, 100 to 150 mph (160 to 240 km/h). They can do as much damage as a small tornado. Microburst - a small downburst affecting an area less than 2 1/2 miles (4 km) in diameter with peak winds lasting generally less than five minutes. Macroburst - a large downburst affecting an area greater than 2 1/2 miles (4 km) in diameter with peak winds generally lasting five minutes or longer. Flood Stage - The level or stage at which a stream overflows its banks or the stage at which the overflow of a stream begins to cause damage. Freezing Rain/Freezing Drizzle - Rain or drizzle which falls in liquid form and freezes on impact with cold surfaces to form a glaze on the ground and exposed objects. Funnel Cloud - A rotating column of air, extending from a towering cumulus or cumulonimbus cloud, that is not in contact with the ground. Gustnado - A gust front tornado. A small, weak, short-lived tornado that occurs along a gust front - the leading edge of a thunderstorm, caused by rain-cooled air flowing out from the storm's downdraft. A gustnado is often visible as a debris cloud or dust whirl. Hail - Precipitation in the form of lumps of ice that form during some thunderstorms. Heat Index - The apparent temperature that describes the combined effect of high temperatures and high levels of humidity, which reduces the body's ability to cool itself. Rain/Showers - Rain is a nearly steady and uniform fall of precipitation over an area. Showers are intermittent and/or scattered convective rainfall of varying intensity. Relative Humidity - The ratio of the amount of water vapor actually present in the air to the greatest amount possible at the same temperature. Sleet - Sleet or ice pellets are solid grains of ice formed from the freezing of rain or the refreezing of melted snow, which bounce off the ground and other objects. Squall line - A line of thunderstorms or squalls which may extend over several hundred miles. Tornado - A violently rotating column of air, from a thunderstorm, in contact with the ground. Virga- Precipitation that dries up in the atmosphere and therefore does not reach the ground. Waterspout - In general, a tornado occurring over water. Specifically, it refers to a small, relatively weak rotating column of air over water beneath a towering cumulus or cumulonimbus cloud. A waterspout may rotate counter-clockwise or clockwise. Wind Chill - An apparent temperature that describes the combined effect of wind and low temperature on exposed skin.
See alsoReferences |
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