With up to 20-inches of white stuff expected to fall on parts of the region today, Philadelphia officials this morning declared a snow emergency.

"That means you cannot park on snow emergency routes," said Mayor Nutter. "We have 110 miles of city streets that are snow emergency routes and they are posted. If you park on those streets, your car will be towed or relocated.

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"We need to keep those streets clear. It's a primary part of our snow fighting effort," Nutter said.

City crews were out at midnight preparing for the winter onslaught. Nutter said 600 city employees will be fighting the storm with 300 pieces of equipment.

"The hard work today is going to help us tomorrow as the snow event continues," Nutter said. "Our goal is to get the city full up and operational by Monday morning so people can get to work and students can get to school."

Forecasts call for the winter storm to last 24 hours.

"And we will continue to fight it as long as it lasts," Nutter said.

Nutter said crews will "aggressively attack" primary and secondary streets first and will do all they can to deal with smaller neighborhood streets as the snowstorm continues.

He will be roaming the city throughout the day, he said, after taking care of a few things at City Hall.

"I've got no plans to hunker down at home, I'll be on the streets all day," Nutter said. "I don't know when I'll see my family again. But I only have one set of clothes, so I'll have to go home sometime."

Contact staff writer Sam Wood at 215-854-2796 or samwood@phillynews.com.