Colorado has declared a state of emergency as it copes with its second major snowstorm in a week.

The storm dumped 20 centimetres of snow on Denver on Thursday night and Friday, forcing highways to close and airlines to cancel flights.

Another 20 cm is expected to fall in the city by Saturday night, said CBC News meteorologist Natasha Ramsahai.

She said cities in the mountains and foothills saw more snow — 45 cm fell on Boulder and 58 on Genesee.

Colorado Governor Bill Owens declared a statewide disaster, just as he did during the storm on Dec. 20 and 21. The declaration means the National Guard is on standby, ready to help with rescues and cleanup.

At Denver International Airport, where 4,700 passengers were stranded in last week's storm, United Airlines and Frontier Airlines cancelled 513 flights on Thursday and Friday.

"Right now, we're planning to operate a full schedule starting at noon (MT)," United spokeswoman Robin Urbanski said early Friday.

Greyhound buses also cancelled service out of Denver, but the city's public transport was still operating Friday.

Ramsahai said this week's storm is different because it is stretching out over several days.

Last week's storm was quick and ferocious, dumping half a metre of snow on Colorado in just 24 hours. Airport and road plows couldn't keep up.

Schools, malls, offices and highways were forced to close and 1,000 flights were cancelled at the airport.

With memories of that storm still fresh, New Year's travellers jammed the Denver airport Thursday in an attempt to get out of Colorado.

Managers at the fifth-busiest U.S. airport drew up snowplowing plans, and airlines urged ticket holders to get early flights or wait until after the storm.

Freezing rain coming to Canada

Canada will feel the brunt of the storm on the weekend, Ramsahai said.

Northwest Ontario and Southern Manitoba will get five to 10 cm of snow Saturday night.

Communities from Thunder Bay, to Sault Ste. Marie, to Sudbury will see freezing rain Sunday. Areas to the north of that line will see snow.

Those to the south, including the Toronto area, will see rain. Ramsahai warns it won't be a pleasant shower.

"It will be a raw, windy rain," she said.

The Ottawa area will see freezing rain Sunday night or Monday.

With files from the Associated Press