Lightning and the surface winds are approaching. Also an interesting streak on this photo which is not on the adjacent photos taken a second before or after....lightening had just struck in the direction of the streak. Could this be a momentary marker of the path of it as it plowed through the dust in the air that this heavy winded front brought up into the sky? I doubt if anyone can really tell, but I do know it wasn't a lense flare or a dirty lens.