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What is a SPC Category?

Severe Weather Outlooks Explainer

SEVERE WEATHER RISK – When we talk about severe weather and that there's a certain "risk" for a day, what does that mean you can expect? Meteorologist Meredith Garofalo breaks down the Storm Prediction Center categories to help you prepare for what's expected on a given dayMORE —>

Posted by WeatherNation on Friday, March 1, 2019

Marginal Risk, Slight Risk, Moderate Risk…terms we use as meteorologists to signify a Severe Weather Day for you.

These forecasts come from the Storm Prediction Center (SPC), located in Norman, Oklahoma.

There are five severe thunderstorm risk categories, all relating to the probability of a severe weather event within 25 miles of any given location.

The outlook also factors in how widespread or intense an event might be.

A severe thunderstorm is defined by the National Weather Service as one with measured wind gusts at least 58 miles per hour, hail at least one inch in diameter, and/or a tornado.

A Marginal Risk means storms could be spotty, and typically will be limited in duration and/or intensity.

Even though this threat level is on the lower end, you should still take it seriously:  tornadoes, damaging wind, and large hail are all possible.

A Slight Risk means scattered powerful thunderstorms are expected.

While storms may be short-lived, they can be intense.

Within the risk area, storms could produce tornadoes as well as isolated areas of wind or hail damage.

An Enhanced Risk means numerous severe storms are expected over the risk area.

Coverage of storms will be more widespread than the previous threat levels, once again, hail, wind damage, and tornadoes are possible.

A Moderate Risk means severe thunderstorms will be more widespread within the area, potentially longer-lived storms, and even more intense than the first three categories.

A day with a moderate risk level on the SPC scale often holds potential for strong or long lived tornadoes, and extensive wind or hail damage.

Then, there’s the fifth category,  High Risk.

This threat level is not common — it is the most severe and should be taken very seriously.

Storms could potentially bring catastrophic damage.

In high risk days, strong, long track tornadoes are possible, as well as widespread damaging winds or extremely large and damaging hail.

Just remember, severe storms can happen anywhere, any time of day.

That’s why it’s important to always stay with WeatherNation when there’s even the slightest threat for severe weather in your neighborhood..

For WeatherNation, I’m Meteorologist Meredith Garofalo

About the author
Meredith is a Certified Broadcast Meteorologist as designated by the American Meteorological Society.  She was born and raised in Cleveland but has worked from coast to coast covering almost every type of weather.  Meredith is a weather, space, and STEM journalist and has been live out in the field during destructive tropical storms on the Gulf Coast of Florida, raging wildfires in Southern Cali... Load Morefornia, and covered the wreckage from tornadoes in the Great Plains. In 2009, she reported on the damaging hail storm during the Sturgis Motorcycle Rally and in 2017, the historic California winter storms that produced record rain totals and devastating flash flooding.  Prior to joining WeatherNation, Meredith worked at KEYT/KKFX in Santa Barbara, CA, KOTA-TV in Rapid City, SD, WWSB-TV in Sarasota, FL, and began her career as an intern at WGN-TV in Chicago.  She was Santa Barbara's "Favorite Weathercaster of the Year" in 2016 and the Community Partner of the Year in 2017 for her volunteer work with Make-A-Wish Tri-Counties and awarded with the 2018 Valparaiso University Alumni Association First Decade Achievement Award. Meredith is the current chair of the American Meteorological Society's Station Scientist Committee, which focuses on raising greater awareness & outreach when it comes to science education for viewers.  She's also an accomplished journalist, producing weather and science stories including rocket launches at Vandenberg Air Force Base and the new GOES-16 satellite and it's impacts on weather forecasting.  Meredith was personally invited by NASA's Johnson Space Center to interview astronauts on the International Space Station and was the only meteorologist in the nation to do an exclusive report accompanying the GOES-West satellite from Colorado to Florida, reporting on and covering it's launch in 2018.  Meredith's also worked on features that took her paragliding along the coast, white water rafting in Northern California, learning to surf in the Pacific Ocean, and how to be an aerial photographer while flying a single engine plane! Say hi on Facebook, Twitter, & LinkedIn!