The 5 Freeway was reopened through the Grapevine Thursday after a storm blanketed the mountainous area with snow, causing a traffic jam that stretched for miles and lasted for hours.
All northbound lanes were reopened about an hour after the California Highway Patrol said it the southbound lanes were open again via escorts.
The 5 was closed Thursday morning after snow created dangerous conditions for vehicles trying to pass through the major throughway.
CHP had dubbed the SigAlert, "Operation Snowflake."
Earlier in the day, Caltrans had warned that the snow was causing "major traffic problems" in the Grapevine and Lebec areas along the interstate, with vehicles sliding across the snow-slicked road.
The National Weather Service tweeted out a Caltrans image of the Tejon Pass, showing the 5 Freeway at Frazier Mountain covered in a layer of fresh white powder around 10 a.m.; the agency also warned of "major travel impacts" in the area.
By 1 p.m., the traffic backup extended for miles, with motorists appearing to be stopped just ahead of an exit ramp in Gorman, Sky5 video of the scene showed.
One motorist said he had been stuck in traffic related to the closure for some three hours, though he noted the traffic was "slowly improving" as of 11:20 a.m.
Forecasters said that a storm system bringing heavy rain to much of Southern California could bring as much as 6 feet of snow to elevations above 6,500 feet.
By 9:30 a.m., some 4 inches had fallen in Frazier Park, the weather service reported.