Textbook SLC? "Scary Looking Cloud"

[GALLERY=media, 1039]Slc1 by Malcolm Shuttleworth posted May 5, 2016 at 9:05 PM[/GALLERY]Hey friends! Just wanted to share this strange cloud formation I observed while tracking some weak thunderstorms northeast of Weyburn Saskatchewan. Looks like a tornado and it even has what looks to be a horseshoe shaped clear slot right where you'd expect it to be. I didn't notice any visable rotation however and it certainly wasn't being detected by radar. There was also an oil fire just to the right of the lowering in my picture. I'm wondering if the smoke from it made this lowering appear more dramatic. So what do you guys think is this simply a SLC? (which is my guess)