Severe Weather Terminology

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Updated: 8:13 AM Apr 6, 2005 Severe Weather Terminology Severe Weather Terminology Posted: 8:13 AM Apr 6, 2005

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The best resource you can have in a severe weather situation is accurate, timely information. When severe weather hits Western Wisconsin, the SkyWarn13 Team is your first choice for weather information. Understating the terms used can help you be better prepared to respond to any severe weather situation. Here are some of the terms that you might hear from the SkyWarn13 Meteorologists during severe weather events.

TORNADO WATCH
Conditions are favorable for the development of tornadoes in and close to the watch area. Watches are usually in effect for several hours, with a six hour duration as the most common.

TORNADO WARNING
Tornado is indicated by radar or sighted by a trained weather spotter.

*Tornado warnings include the location where the tornado was spotted, the direction the tornado is moving and the speed of movement. Towns near the tornado are also listed, with the entire county that the tornado was spotted in under the warning. Periodically, more than one county will fall under the same tornado warning.

SEVERE THUNDERSTORM WATCH
Conditions are favorable for the development of severe thunderstorms, along with isolated tornadoes. Watches are usually in effect for several hours, with a six hour duration as the most common.

SEVERE THUNDERSTORM WARNING
Severe thunderstorms have been indicated by radar or sighted by a trained weather spotter. A severe thunderstorm warning is issued when winds are 58 miles per hour or greater and/or hail is 3/4 inch in diameter or larger.

*Severe thunderstorm warnings include the location of the center of the severe thunderstorm, direction of movement and speed at which the storm is moving. Towns near the severe thunderstorm are also listed, with the entire county that the severe thunderstorm was spotted in under the warning. Occasionally, more than one county is under the same warning.

URBAN/SMALL STREAM FLOOD ADVISORY
This advisory alerts the public to flooding, which is generally only an inconvenience (not life-threatening) to those living in the affected area. They are issued when heavy rains will cause flooding of streets and low-lying places in urban locations. Also used if small rural or urban streams are expected to reach, or exceed their banks. Some damage to roads or homes could occur.

FLASH FLOOD WATCH
This indicates that flash flooding is possible in or close to the watch area. Those in the affected area are urged to be ready to take action if a flood warning is issued, or flooding is observed. Flash flood watches are usually issued when flooding is expected to occur within 6 to 12 hours after heavy rains have ended.

FLOOD WATCH
This indicates that widespread flooding is a possibility in or close to the watch area. Those in the affected area are urged to be ready to take action if a flood warning is issued, or flooding is observed. These watches are issued for flooding that is expected to occur within 6 to 12 hours after heavy rains have ended.

FLASH FLOOD WARNING
A flash flood warning is issued for life/property threatening flooding that will occur within 6 hours. It can be issued for rural or urban areas, as well as for areas along major rivers. Dam breaks or ice jams can also create flash flooding.

FLOOD WARNING
A flood warning is issued for life/property threatening flooding that will occur 6 to 12 hours from the time of issuance for widespread areas. It can be issued for rural or urban areas as well as for areas along major rivers.

FLOOD WARNING (RIVER)
Used to inform the public of long-term (more than 12 hours) flooding along major streams and rivers, which is a serious threat to life and property. This warning usually contains river stage forecasts.

HEAT ADVISORY
Issued when daytime heat index values (humiture) of 105 Fahrenheit or above are expected, along with nighttime heat index (humiture) minimums of 80 Fahrenheit or above for two or more consecutive days. This advisory is issued when heat becomes an inconvenience and only a problem for a minor portion of area residents.

EXCESSIVE HEAT WARNING
Issued when the heat index (humiture) is expected to exceed 120 Fahrenheit or greater for three or more hours. In these cases, the heat becomes dangerous for the majority of area residents.

DENSE FOG ADVISORY
Used when dense fog covers a widespread area and reduces visibility to 1/4 mile or less.

WIND ADVISORY
This is issued when sustained winds of 30 miles per hour or greater are expected to last for 1 hour or more. Also used for wind gusts of 45 to 57 miles per hour for any duration.

HIGH WIND WARNING
A High Wind Warning is issued when sustained winds of 40 miles per hour or greater are expected to last for at least 1 hour. Also issued if wind gusts are expected to reach 58 miles per or greater for any duration.

FROST ADVISORY
Frost advisories are issued during the growing season when overnight lows are expected to reach levels that can produce widespread frost (usually temperatures in the 30's).

FREEZE WARNING
Issued during the growing season when temperatures are expected to drop well below freezing over a widespread area for an extended period of time. This warning is issued regardless of whether frost forms or not.