Update: remarkable "smoke cyclone"/ "smokestorm" has now moved south into central U.S., crossing the Canadian border near the MT/SD border. This low pressure system has entrained a massive amount of smoke from numerous large boreal forest fires in central Canada.#MTwx #SDwx #COwx https://t.co/Z80zPIFciJ pic.twitter.com/SzMk1zzq7e

— Dr. Daniel Swain (@Weather_West) May 21, 2023