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Storm Prediction Center (SPC)
The Storm Prediction Center is a branch of the NWS and provides data to the public about severe weather as well as other hazardous weather.
Severe Weather
The SPC issues probability maps for days 1 through 8, but in different forms. The day 1 always provides the probability of tornadoes, wind, hail, and the risk of severe weather. Days 2 and 3 only provide the risk and probabilistic outlook for any severe weather type. Days 4 through I provide only the probability of severe weather in general.
Risk Classifications of Severe Weather
Severe weather is classified by the SPC in 6 ways:
- General thunderstorms - weak thunderstorms, maybe a few with 40mph winds and small hail.
- Marginal risk - chance of spotty damaging winds, spotty hail up to 1“, very low possibly a tornado in the area.
- Slight risk - medium chance of having high winds of 60mph+, hail greater than 1”, low chance of a tornado in the area.
- Enhanced risk - High chance of high winds 60mph+, hail greater than 1“, possibly larger than 2”, medium risk of a tornado in the area.
- Moderate risk - very high chance of high winds 60mph+, hail greater than 1“, possibly larger than 3”, very high risk of a tornado in th area.
- High risk - reserved for definite tornado outbreaks and derechos. Tornadoes almost definite in the area, including strong, long track varieties, winds greater than 70mph likely.
