Reminds me of weather here on the Northern Plains in the mid-continent area of North America. I will be a watcher and post weather pics of my own on my page for you and others. I am a weather enthusiast.
I saw something very similar like that in Texas when I was on the rode. It it just very heavy rain? In this one spot, it was all dark and cloudy with that.. thing... and the rest of the sky had no clouds at all.