According to the California Highway Patrol, both directions are shut. Northbound traffic was diverted at Parker Road in Castaic earlier in the evening, while soutbound traffic was also diverted at Grapevine Road in Lebec.
The closure is expected to last until conditions improve, the CHP said.
The winter blast has reportedly caused several accidents and spinouts in the area. Some drivers who were not expecting the closure are now forced to stay overnight.
"I'm going to end up sleeping in the car, just piling on the sweatshirts and seeing what we can do," said driver Taylor Ingram.
The CHP also had to shut down the Grapevine in the morning due to snow. Shortly after that closure, the CHP began escorting traffic through the Grapevine.
Snow fell elsewhere in Southern California on Thursday. The High Desert community of Oak Hills was hit with snow, and conditions were cold and windy along the Cajon Pass. A steady but light downfall of snow wasn't enough to cancel school and it wasn't enough to deter traffic flow too much on the 15 Freeway either.
However, the roads were slick and icy at times. Caltrans and CHP warned drivers to take it slow. If conditions deteriorate, the freeway may close completely.
State Route 330 was reported clear around midday with no chain requirements. However, highways 18 and 38 required chains on the way up to Arrowhead or Big Bear.
Antelope Valley residents also woke up to some snow. A cold storm moved in overnight, dumping snow as low as 2,000 feet.
Southland communities also dealt with strong winds. A wind advisory was issued until Friday morning for most SoCal areas. Also, a high surf warning was issued until Saturday morning for the Los Angeles and Orange county coastal areas.
Temps hit the mid-50s with scattered rain showers in Los Angeles and Orange counties, the I.E. and Valleys and upper 20s for the local mountains with snow at 4,000 feet.