Severe weather terminology (United States)

Atmospheric ash plume advisories/warnings are also issued by the United States Geological Survey (Aviation Color Codes).

The National Weather Service also relays messages for non-weather related hazardous events in text products and NOAA Weather Radio broadcasts:[54][55] Wind alerting is classified into groups of two Beaufort numbers, beginning at 6–7 for the lowest class of wind advisories.

In order of increasing risk, these statements are: The Storm Prediction Center (SPC) issues Day 1, Day 2, and Day 3 Convective Outlooks depicting forecast areas of general (non-severe) and severe thunderstorm threats across the contiguous United States, along with a text narrative discussion consisting of a plain-language summary of the threat type(s) and timing focused on areas of highest risk, and a technical discussion written in scientific language that usually includes a synoptic overview of convective patterns as well as, if necessary, a geographically specific narrative of meteorological reasoning and justification for the type of coverage and intensity applicable to the severe thunderstorm threat.

The impact statement system—initially used only for tornado and severe thunderstorm warnings—was first employed by the WFOs in Wichita and Topeka, Kansas, and Springfield, St. Louis and Kansas City/Pleasant Hill, Missouri beginning with the 2012 Spring severe weather season, eventually expanded to include 33 additional National Weather Service Weather Forecast Offices within the Central Region Headquarters in 2013, and then to eight additional offices within the Eastern, Southern and Western Regions in the spring of 2014.

[69][70] Under this system, the warning product will include text denoting the specific hazard (i.e., 60 mph wind gusts and quarter size hail) and applicable sourcing (either via indication from Doppler weather radar, or visual confirmation from storm spotters or other emergency management officials) and the level of impact to life and/or property.

In order of increasing risk by warning type, these statements—which may be modified at the discretion of the regional forecast office—are:[71] (For landspouts and weak tornadoes, alternative impact statements may be utilized at the discretion of the Weather Forecast Office; all other statements are standard nationwide.)

Alternate wording: Alternate wording: Hazardous weather forecasts and alerts are provided to the public using the NOAA Weather Radio All Hazards system and through news media such as television, radio and internet sources.

Many local television stations have overlay graphics which will either show a map or a list of the affected areas.

The Beaufort scale is an empirical measure that correlates wind speed to observed conditions at sea or on land.