A one-two punch of storm systems moving into California this week will bring rain, snow, flooding, and travel issues into play across the Golden State.

While it has been a lackluster start to the rainy season in California, two systems will bring rain and snow this week. As of Dec. 15, the statewide snowpack sits at around one-third of its average for this time of year. However, rain and mountain snow are in the forecast this week and should help increase the numbers.

The WeatherRadar shows rain and snow spreading across California on Monday as a front moves onshore, kicking off a wet pattern that will last into Tuesday. While the front is responsible for round one of lower-elevation rain and high-elevation snowfall, round two of rain focuses on the southern half of the state as a storm system develops on Wednesday and sends moisture inland through the remainder of the week.

The WeatherRadar shows rain and snow stretching along the West Coast from Washington to Southern California on Monday. Rain is in the forecast for cities such as Seattle, Portland, Ore., San Francisco, and Los Angeles. A few thunderstorms may also develop along the coast of California, producing lightning and small hail. Snow will be confined mainly to the higher elevations of the Sierra.

The wet weather continues on Tuesday while the first storm system drifts north and pulls the bulk of its rain into the Pacific Northwest. The second storm system will develop off California in its place, bringing more rain, especially for southern California for the second half of the week.

A wet forecast is in place for Los Angeles and Southern California from Thursday into Friday, with the moisture eventually spreading into the Desert Southwest over Christmas weekend. Through the end of the week, coastal California could see 3-5 inches of rain, with 1-2 inches expected inland and into the Desert Southwest. Mountain snow could amount to 12-18 inches in the highest elevations, with some locations seeing up to two feet in the southern Sierras.

The biggest concern will be flooding and landslides, especially in coastal California, through the remainder of the week. Turn on your Weather & Radar app alerts now and monitor conditions on the WeatherRadar before traveling.