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

Check out this incredible video shot by Edgar ONeal in 360 of the massive shelf cloud with tornado warnings! IT’S BEHIND US! | Reed Timmer Extreme Meteorologist

Time Lapse: A menacing shelf cloud sweeps over Beaumont, #Texas on Saturday, right after a strong tornado moved through West Port Arthur. #storm #stormchasing | Texas Storm Chasers

Aliens?! 😲🛸 This storm produced a tornado moments before this! 🌪 Incredible structure on this mothership shelf cloud as it chase us across Alberta, Canada. #TornadoWatch #StormChasing #Tornado | Ricky Forbes

A wild arcus cloud rolled over Daytona Beach 👀 | Clime