37 reactions · 4 comments | A massive arcus cloud approaches our position ahead of a cluster of supercells in Nebraska. This occurs when storms become outflow dominant and produce a pool of cold air. The dense, heavy air creates a wedge that pushes warm, moist air upward causing linear, often striated arcus clouds like this one to form. They are scary looking, but harmless...mostly. Video: Martin Lisius. | Tempest Tours | Facebook