This image is in the public domain because it was stored on the web servers of the U.S. Storm Prediction Center, which is part of National Weather Service. NWS-created images are automatically public domain in the U.S. since the NWS is a part of the U.S. government.
Thus all images on SPC servers are public domain.
Captions
The Storm Prediction Center Severe Weather Outlook on February 26, 2022