LAS VEGAS (KLAS) — Those leaving Las Vegas after the holiday weekend should prepare for long delays. According to a noon tweet from RTC Southern Nevada Monday, heavy holiday traffic has caused an 18-mile backup to the Nevada-California state line.

Travelers heading to Arizona should expect slow traffic and delays on I-11 South, from College Drive through Railroad Pass.

A seven-mile backup was seen on the I-15 south to California Sunday as travelers left Las Vegas after the New Year’s holiday, according to RTC Southern Nevada.

A tweet from RTC around 4 p.m. said, “7 Mile backup to NV-CA Stateline.”

RTC advised drivers to prepare for delays and winter weather as they leave the Las Vegas valley.