A shelf cloud (or arcus cloud) making its way toward our office just a little before 9 PM this Tuesday evening, leading in the next narrow line of showers and gusty winds. https://cloudatlas.wmo.int/en/clouds-supplementary-features-arcus.html | US National Weather Service Spokane Washington

WATCH: Unbelievable shelf clouds rolling in over Lviv, Ukraine. Dmytro Shvets shared this spectacular video on Instagram. So what is a shelf cloud? A shelf cloud, also known as an arcus cloud, forms at the leading edge of thunderstorms. It is formed when the cooler air of a thunderstorm encounters warm, humid air and lifts it. It announces the arrival of storms. If you see a shelf cloud coming your away, it probably means you are about to get hit by a strong thunderstorm. #Cloud #ShelfCloud #Spe