The Storm Prediction Center (SPC) is always looking for ways to improve the way it communicates potential weather threats to the general public, and starting on Wednesday, October 22nd, we will see a change in the outlook maps as the agency takes it to the next level. While there have always been Day 1, 2, and 3 maps that show what is called a categorical risk, the shading and wording of those maps will be enhanced.
After asking for feedback from users, including the general public, and taking into consideration how specific wording affects the way people respond to information regarding weather, the SPC will change its current descriptions from "see text," "slight," "moderate", and "high" risk. Those latter three words have been used for almost 35 years, so this change is kind of a big deal in the meteorological community.
The word "marginal" will replace "see text," with a new contour to depict the specific region with that marginal risk. Until now, "see text" literally required reading the text explanations that accompany the outlook maps, which can be lengthy and quite lingo-heavy, in order to gain insight into what specific types of severe weather may occur. The hope is that the contour and "marginal" label in the map will be a little more clear from the first glance.
"Slight" risk is now being split into two categories because it was felt that the one category was too broad. It may cover a 15% chance for severe thunderstorms with high wind and hail or the 10% probability for a significant tornado, which would be EF-2 or greater on the Enhanced Fujita scale. Now that 10% chance for a strong tornado will be included in the "Enhanced" risk, which is on the higher end of what was the "slight" risk scale.
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The goal in making these simple changes is to help those who use the outlooks for personal reasons and those who use them to help communicate weather risks to the public gain some additional clarity at first glance when they look at the maps. The hope is that with these improvements, planning will be easier for the threats and more lives will be saved when severe weather occurs.
For a more definitive explanation and examples of how the new maps will look, check out the Storm Prediction Center's website.