The volume and direction of debris flows are "completely unpredictable," fire officials warned.
"We are involved in a race against Mother Nature and if she wins the race there is no way that we can assure that firefighters...will be able to get into your neighborhood and make a rescue," L.A. County Fire Chief P. Michael Freeman said.
L.A. County Sheriff's Capt. David Silversparre said that the evacuation is expected to last a minimum of 96 hours, and that residents need to be prepared to be away from their homes through Sunday.
"We wish people to be prepared to leave, and to be cooperative when they're leaving," Silversparre said.
Evacuation centers have been set up at La Cañada High School, the Glendale Civic Auditorium and the Sunland Recreation Center. Local schools will remain open and accessible, officials said.
Christopher Stone, assistant deputy director with county public works, said that one of the biggest public safety issues in the coming days will be access to affected properties and residents.
"Don't park on any of the [evacuated] streets," Stone said. "If you have been asked to evacuate and you've got an extra car, put them in the garage or put them in the driveway."
Individuals who do not live in the impacted areas were also ordered to stay away.
Paradise Valley resident Pat Anderson said Tuesday night that her car is still packed packed from the mandatory evacuation on Monday. She has made arrangements to stay in a nearby hotel, she said, but hopes the storm will be less severe than predicted.
