Severe weather threat: Breaking down risk levels from marginal to high
April marks the start of severe weather season in Minnesota
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With April and severe weather season on the horizon in Minnesota, understanding the severe weather risk levels used by the National Weather Service Storm Prediction Center can make all the difference, from isolated storms to high-risk outbreaks.
Let’s break down each risk level and its meaning.
Decoding the Storm Prediction Center’s thunderstorm risk levels
As March turns into early April, the transition into spring becomes more noticeable in the warming temperatures and changing weather patterns. This period also marks the start of peak severe weather season across the central Plains and the broader United States.
When warm, moist air from the south collides with cooler, drier air from the north, it creates ideal conditions for powerful thunderstorms capable of producing severe weather.
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These storms can bring damaging winds, large hail, and even tornadoes. That’s why it’s important to understand the Storm Prediction Center’s risk levels and what they mean for our safety.
The Storm Prediction Center issues daily outlooks that categorize the risk of severe thunderstorms using a simple, color-coded scale.
The five levels of severe weather risk
Severe thunderstorms are rated by the SPC on a five-level scale, reflecting the growing severity, from isolated storms to widespread, life-threatening events.
1. Marginal risk (Dark Green)
At this level, isolated severe thunderstorms are possible. These storms are typically limited in duration, coverage, and intensity. While brief gusty winds or small hail may occur, widespread impacts are unlikely.
2. Slight risk (Yellow)
A slight risk signals scattered severe storms. Though not widespread, storms may be more organized and capable of producing hazards like hail, gusty winds, or even a brief tornado.
3. Enhanced risk (Orange)
Conditions now favor numerous severe storms with greater coverage and persistence. Hazards may include damaging winds, large hail, frequent lightning, and possible tornadoes.
4. Moderate risk (Red)
This category indicates widespread, long-lasting, and intense severe weather. Multiple storms may produce significant damage, including strong winds over 70 mph, large hail, and several tornadoes. Situations like these often lead to organized severe weather outbreaks.
5. High risk (Magenta)
The most dangerous and rare category, High risk is issued only a few times per year. It signals a major severe weather outbreak, often involving strong, long-track tornadoes or destructive wind events such as derechos.
Understanding what the scale really means
One of the most important things to remember is that these categories represent probability, not certainty. Each level reflects the likelihood of severe weather occurring within 25 miles of a point, not necessarily directly over your home.
Even areas outside the severe categories, those labeled simply as general thunderstorms, can still experience dangerous lightning, heavy rain and other severe weather hazards. No thunderstorm should ever be considered completely harmless.
As we enter severe weather season, understanding the SPC’s risk ratings can help you stay prepared and safe if storms strike, and your MPR News weather team will keep you updated every step of the way.
