Weather Geek Speak: Severe weather categories explained

When severe weather is lurking in the neighborhood, you'll likely see social media posts referencing "SPC" risks such as "Slight" or "Enhanced" or "Moderate". Here's what they mean:

When severe weather is lurking in the neighborhood, you'll likely see social media posts referencing "SPC" risks such as "Slight" or "Enhanced" or "Moderate." An example might be: "SPC giving Enhanced Risk of severe weather over Oklahoma today while north Texas is in the Slight Risk category."

"SPC" refers to NOAA's Storm Prediction Center, based in Norman, Oklahoma and monitors severe weather threats around the nation. When severe weather is possible, they will issue color-coded risk categories over geographic areas that represent the level of perceived threat.


A light green shade indicates just a risk of general thunderstorms but not reaching severe levels. From there, the risk levels get a name:

According to NOAA, marginal means a risk of isolated severe storms that are expected to be limited in coverage and/or intensity. "Slight" Risk means scattered severe storms are likely, but they would be short-lived and/or not widespread.

Once you get into the Enhanced and higher risk categories, the confidence increases of a potential widespread or regional severe weather outbreak. Moderate risk means widespread severe storms are likely, including long-lived and intense storms. 

The "High" risk category is reserved for the most dangerous of severe weather outbreaks and means widespread severe storms are expected, with particularly intense, long-track tornadoes likely. This risk category might only be issued a handful of times a year, if not even less.

SPC will also issue outlooks for possibilities for tornadoes, large hail or damaging winds inside severe storms. Hatched areas show an additional risk of upper-end severe weather events, such as tornadoes of EF-2 to EF-5 strength on the Enhanced Fujita Scale. 

On this particular day, strong tornadoes were a concern across much of Missouri and into northern Arkansas.

SPC issues maps for the current day and individual maps for the next day and the day after, plus a general extended forecast. So it's an excellent resource for planning over the next few days to see if severe weather is possible.

In addition, SPC issues Fire Weather Outlooks using a similar colored risk scale with three levels of Elevated, Critical and Extreme. 
 


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