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Weather Academy: Severe Weather Risk Levels Explained

Published: Mar. 28, 2022 at 6:06 AM CDT
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MONROE, La. (KNOE) - Today on the Weather Academy, we discuss severe weather risk categories. The threat of severe weather is back in the forecast as we head into this week. You’re likely going to hear us as meteorologists talk about the different types of severe weather outlooks issued for our region.

Severe Thunderstorm outlooks are issued by the Storm Prediction Center, located in Norman, Oklahoma. The outlooks highlight areas that have a chance of seeing severe storms and show how high that risk is based on the probability of a severe weather event occurring within 25 miles of a given location. And just a reminder that the criteria for a severe thunderstorm are defined as this: winds gusting at least 50 miles per hour, hail of at least one inch in diameter, and/or the storm capable of producing a tornado or two.

The SPC uses a scale that ranges from level one to level five, with level one being a marginal risk. At the Marginal Risk is when we have the possibility of seeing isolated storms, short-lived storms at that very limited intensity, with only one or two of those systems becoming severe. And those storms are just reaching that criteria to be a severe thunderstorms.

As we continue up our scale here and start to look at that Slight Risk or level Two out of five on our severity scale, we start to see scattered, but still, short live systems or intensity is slightly better but still limited. We’re only seeing one or two intense storms packing a little more of a punch, though, in terms of our possible threats.

Once we reach out of that level two threat and go into a level three or an Enhanced Risk for severe weather, we start to see numerous storms, scattered storms, and persistent storms. That means they’re lasting a little bit longer, becoming a little bit more intense, and we’re starting to see damage start to add up possible wind reports also, large hail, and even a few tornadoes expected within that enhanced risk.

At a level four, that’s what we’re really starting to see impacts. Strong tornadoes are possible within this moderate risk or level four out of five and our severity scale, and strong tornadoes mean EF three or higher. We’re also seeing widespread severe storms that are longer lived and have a lot more intensity associated with them.

At level five, the highest level, we expect to see that high-risk level five out of five in our severity scale. That’s when we see quite a bit more impacts. Widespread severe storms, long-lived and particularly intense storms are all possible. High-risk days are very rare. They are usually around to derecho events, tornado outbreaks, and days that significant damage is expected to be widespread across a region.

In fact, over the last three years, we’ve only seen three days that have had a high risk implicated. The last time the SPC Outlook issued a high risk was March 25, 2021. On this day, we saw multiple tornadoes, at least one within this region. Multiple tornado emergencies were issued for at least three different tornadoes that occurred. And that’s why it’s so important to know the difference between these categories. You want to have a plan in place ahead of these storms and make sure that you have multiple ways to receive weather alerts and stay weather aware.

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