As millions of Californians prepare to embark on their holiday travels, a severe weather system looms over the state, potentially causing delays and hazardous conditions. The National Weather Service has issued a flood watch for over 20 million people across Southern California, including Los Angeles, as an atmospheric river poses a threat of flooding and mudslides.

Following closely on the heels of a recent system that hit California on Tuesday, another storm is projected to move across the Golden State from Wednesday through Friday. The National Weather Service office in Los Angeles warns that this stronger storm will bring several hours of steady moderate to heavy rain and gusty winds, heightening the risk of flooding and thunderstorms.

Rainfall has already begun in Northern California, gradually making its way south throughout Wednesday. The storm is expected to peak in Southern California on Thursday, with a few lingering showers continuing into Friday. The Weather Service also cautions that high-resolution models indicate a low but non-zero threat of rotation in the storms, which could potentially result in waterspouts or small tornados, particularly between Point Conception and coastal LA County.

The magnitude and rate of rainfall anticipated has prompted concerns regarding flash flooding. Widespread rainfall of 2 to 4 inches is expected along the coast, with up to 8 inches possible in the mountains. Los Angeles could receive more than a month's worth of rain in just a few days, leading to the possibility of significant flash floods, urban flooding, and mudslides, especially over areas scarred by recent wildfires.

In addition to the heavy rainfall, significant snowfall is predicted in portions of the Sierra Nevada. The highest peaks could see an additional 6 to 12 inches of snow. By Friday, the system will push the moisture farther east into Arizona, Utah, and Nevada. Gusty winds of 20-30 mph will also pose a challenge for travelers in these states, potentially leading to hazardous travel conditions as the holiday weekend approaches.

Californians heading out on their holiday journeys are advised to exercise caution and stay updated on the changing weather conditions. Local authorities are closely monitoring the situation and taking necessary precautions to ensure the safety of residents and travelers.