DENVER (AP) — A major snowstorm has hit Colorado, closing numerous schools and government offices Thursday and shutting down sections of highways leading to the Denver area as meteorologists warned of difficult to nearly impossible travel.

“Our city hasn’t seen a storm like this in a few years,” Denver Mayor Mike Johnston posted Wednesday on X, formerly known as Twitter.

The storm, which began Wednesday night, wasn’t expected to wind down until Friday. The heaviest snow accumulations were expected in the Front Range Mountains and Foothills, with a large area expected to get 18 to 36 inches (45 to 91 centimeters), and some amounts exceeding 4 feet (1.2 meters), the National Weather Service said.

Sections of Interstate 70 were closed in the Colorado mountains.

“Huge flakes coming down hard,” the weather service’s office in Boulder posted on social media early Thursday.

The storm started as rain in the Denver area and turned into snow. The area was expected to get 10 to 20 inches (25 to 50 centimeters) of snow, with up to 2 feet (60 centimeters) in the western suburbs, the weather service said.

Denver deployed 36 residential plows starting at 3 a.m. Thursday with the plan to shave the top few inches of snow off streets, to help clear paths to main streets.

Denver International Airport was open early Thursday, but at least several hundred flights to and from there were canceled or delayed, according to Flightaware.com.

The snowstorm comes as other parts of the country face severe weather. Massive chunks of hail pelted parts of Kansas and Missouri on Wednesday night, with storms unleashing a possible tornado in Kansas.