(KTXL) — Consistent heavy snowfall in the Sierra Nevada has forced some chain controls and closures on the major roadways through Eastern California.

Video above: Winter Weather hits the foothills east of Sacramento

Overall mountain travel is discouraged for the remainder of Thursday and going into Friday as conditions worsen.

Caltrans said that in California there are three levels of chain requirements:

– Requirement 1 (R1) states that “chains are required on all vehicles except passenger vehicles and light-duty trucks under 6,000 pounds gross weight and equipped with snow tires on at least two-drive wheels.”

– Requirement 2 (R2) states that “chains or traction devices are required on all vehicles except four-wheel/all-wheel drive vehicles with snow-tread tires on all four wheels.”

– Requirement 3 (R3) states that chains are required on all vehicles.

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According to Caltrans, Requirements 1 and 2 are the most common chain control requirements. Often, highways will be closed down before requirement 3 is put into effect.

As of 5:15 p.m. Thursday, these are the chain controls in the Sierra Nevada:

Interstate 80

I-80 is closed in both directors from Colfax to the Nevada State line due to no visibility and high winds, according to CHP Truckee.

There is no estimated time the roads will reopen.

Highway 50

As of 8:30 p.m., traffic was released on Highway 50, according to Caltrans.

Highway 20

The roadway has been closed to traffic at Nevada Street in Nevada City.

State Routes

State Route 89 is closed at Emerald Bay due to avalanche control.

SR-89 also has R1 chains controls from Truckee to Tahoe City

State Route 88 Carson Pass and Carson Spur are open.

State Route 267 has R2 chain controls from Northstar to Kings Beach.

State Route 28 has R2 chain controls from Tahoe City to Kings Beach.