The Storm Prediction Center or the SPC, puts out a convective outlook each day. These outlooks show where there could be thunderstorms or severe thunderstorms in the United States for the next couple of days.
They then rank the severe threat into categories, to help us forecast and plan when severe weather could strike.
Here are the Categories:
Light Green: Used to signify thunderstorms, but not severe.
Dark Green: Considered Marginal Risk for severe storms. This means there could be one or two severe storms, but not widespread.
Yellow: Means a Slight Risk for severe storms. This means it could be a short-lived event, but not widespread.
Orange/Brown: Signifies an Enhanced Risk for severe storms. This means it could be widespread, with a few intense storms.
Red: This means a Moderate Risk for severe storms. Moderate indicates that there could be a long-lived, widespread event.
Magenta: Considered a High Risk for severe storms. If this is issued it is expected to be a widespread, long event, with intense storms.
Here is what an outlook looks like: