Officials in communities across Washtenaw County are urging residents not to park their vehicles in the streets as they prepare for a blizzard expected to dump 12 to 13 of inches of snow on the area. A blizzard warning goes into effect at 7 p.m.

Kirk Pennington, Ann Arbor street maintenance field operations supervisor, said people who must park their vehicle in the road should park "tight to the curb" and "anticipate it being buried in."

He said snow plows will clear priority streets first — those with higher traffic volumes or which lead to public institutions. Among those streets are Plymouth Road, Stadium Boulevard, Washtenaw Avenue, Packard Street, Ann Arbor-Saline Road and Main Street.

Crews are not expected to begin clearing residential streets until 7 a.m. Wednesday, with trash routes taking priority, Pennington said.

Pennington said continuing snow fall and wind could cause snow to drift back onto previously plowed roads and visibility could be poor.

The City of Ypsilanti has already declared a snow emergency for Tuesday. The city sent out a statement asking residents not to park on city streets. It said the snow emergency would be in effect until City Manager Ed Koryzno cancels it.

The Chelsea Police Department issued an alert asking residents to refrain from parking on city streets for the next 48 hours, to allow easier passage for plow trucks.

The city's ban on street parking from 2 to 5 a.m. will be strictly enforced, according to the alert.

Jeff Fordice, Saline Department of Public Works director, said in an e-mail that cars parked in the street slow down the plowing process.

"With the amount of snow predicted, it will be difficult to dig out cars that have been plowed in," Fordice said in an e-mail.

Dexter Village officials also asked people to move their cars off the street and from public parking lots as soon as possible.

Already, several organizations are canceling events and closing offices, and Wednesday's trash pickup in Ann Arbor has been delayed. School officials said they could make a decision tonight on classes Wednesday.

Pennington advised area residents to avoid driving during the storm, and said anyone who must travel should have a winter emergency kit with water, blankets, food and other items in their vehicle.

"If you're going to go out, anticipate extremely difficult conditions, bordering on impassable," he said.

Heather Lockwood is a reporter for AnnArbor.com. Reach her at heatherlockwood@annarbor.com or follow her on Twitter.