Severe Weather Awareness: Understanding the Severe Risk Categories

There are 5 severe risk categories. Do you know what they mean & what to expect when your community is under a risk?

Posted: Mar 15, 2021 2:00 PM
Updated: Mar 15, 2021 2:03 PM

The National Weather Service (NWS) and other outlets of weather, such as Storm Team 44, really pride ourselves on keeping the public informed when severe weather is in the forecast. From tracking the storm's timeline, to highlighting which neighborhood has the highest risk, communicating severe threats can sometimes be overwhelming to downright confusing to viewers. As forecasters, we try to cut down on the muddiness by getting ahead of the storm days before it hits. The best way we practice this is by issuing Severe Convective Weather Outlooks.

The Storm Prediction Center (SPC) in conjunction with the NWS are responsible with issuing severe outlooks as early as 8 days prior: Day 1 (or the day of), Day 2 (the day before), Day 3 and Days 4-8). As the impending storm develops and matures the forecasters at SPC is able to get more detailed and exact with the forecasting for the Day 1-3 outlooks. For most, communicating the threat of strong storms is straight-forward. However, conveying a severe weather forecast can get cluttered when it comes to describing the different categories of risk and how does that apply to your preparation. Since 2014, the SPC has issued 5 risk categories that are colorized and numericize: marginal, slight, enhanced, moderate and high.

1- MARGINAL (green): indicates storms of only limited organization, longevity, coverage and/or intensity, typically isolated severe or near-severe storms with limited wind damage, large hail and perhaps a tornado. For reference, a MARGINAL risk is most common in the summer months in the Tri State. In the afternoon a pop up thunderstorm may reach severe limits briefly for one or two locations. 

2- SLIGHT (yellow): Isolated significant severe events are possible in some circumstances but are generally not widespread. The threat exists for scattered severe weather, including scattered wind damage (produced by straight-line sustained winds and/or gusts). This risk also includes scattered severe hail and/or isolated tornadoes which are often of shorter duration and varying weak-to-moderate intensity.

3- ENHANCED (orange):This risk category replaced the upper end of "slight" as of 2014. It differs from the slight risk category by being more concentrated and of varying intensities. For reference, the Tri State was under an ENHANCED risk the evening of March 28, 2020 when two EF2 tornadoes hit the communities of Spottsville, KY (Henderson Co. ) and Newburgh, IN (Warrick Co.). Although the storm left a considerable amount of damage in those areas, there was not a widespread outbreak of destructive storms in the Tri State.

4- MODERATE (red): indicates that more widespread and/or more dangerous severe weather is possible. The seriousness and the destructibility of potential severe storms are ramped up when a MODERATE risk is issued. Numerous tornadoes even some that may be strong and potentially long-track. Also, more widespread or severe wind damage and very large hail (up to or exceeding 2 inches in diameter) could occur. Major events, such as large tornado outbreaks or widespread straight-line wind events, are sometimes also possible on moderate risk days, but with greater uncertainty.

5- HIGH (pink/magenta): indicates a considerable likelihood of significant to extreme severe weather, generally a major tornado outbreak. HIGH risk days includes the potential for extremely severe and life-threatening weather. This includes widespread strong or violent tornadoes which may be on the ground for a half-hour or longer, or very destructive straight-line winds.

Hopefully these descriptions keep you informed and weather-aware through the severe weather season. Storm Team 44 really want to emphasis no matter the category risk your community is under it is imperative to have a plan in place. Weather conditions can, and will continue to change at a moment's notice. The SPC's outlook and threat risk are just tools used to keep the public aware, they are not forecast.

Evansville
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Owensboro
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Mount Carmel
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Madisonville
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Washington
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