DES MOINES, Iowa -- What was supposed to have been light snow, maybe an inch, turned into the type of snow storm that has led to multi-car pileups in the Midwest over the past couple years.

The National Weather Service reports 7 inches of snow fell in Ankeny, north of Des Moines. Nine inches fell in Polk City, a few miles northwest of Des Moines.

It isn't just the amount of snow that led the National Weather Service to issue a rare Snow Squall Warning. It's a sudden, heavy snow that quickly creates white-out conditions and ice and it happened today on I-35 near Ankeny. There were crashes and traffic slowed to a crawl.

Similar conditions led to a 70 car and truck pileup on I-35 in 2018, and a 50 car and truck pileup on I-80 in 2019. WHO13 video below.

With all of these storms, unexpected heavy snow turned the interstate into a snowy parking lot.

"We weren't expecting this much snow across Central Iowa. It's just that conditions came together to produce a band of very heavy snowfall in Central Iowa late this morning into this afternoon." Meteorologist Jeff Zogg with the National Weather Service explains about the sudden heavy snowstorm Monday.

That led the National Weather Service to issue a new kind of warning.

"A Snow Squall Warning is something new. We started issuing them last year." Zogg tells the iHeart Radio Newsroom.

"They call for very heavy snowfall, and/or winds of 40 miles per hour or more, that produce life-threatening travel conditions."

Based on the Iowa Department of Transportation traffic camera screenshot, that's exactly what happened.

Photo of I-35 Snow Squall by Iowa Department of Transportation. Snowfall map gaphic Iowa State University Environmental Mesonet.