HOUSTON (KIAH)— The National Weather Service says an active pattern will bring significant mountain snow and heavy lower elevation rain to the western U.S. into the Christmas weekend.

Snow showers expected across the Great Lakes and Northeast Thursday before switching to a rain and snow mix on Friday. The Los Angeles and San Diego metro areas, forecast to receive 1 to 3+ inches of rain in 24 hours. Given the potential for flash flooding as well as runoff over nearby burn scarred and hydrologically sensitive areas, the Weather Prediction Center has issued a Slight Risk of Excessive Rainfall for portions of southwestern California through Saturday morning.

Over the Sierra Nevada there is potential for 5+ feet of snow to accumulate through Christmas morning, while more moderate totals of around 1 to 4 feet are expected across the rest of the western mountain ranges.

In preparation for the snow and potential for hazardous travel conditions, a menagerie of Winter Storm Watches and Warnings as well as Winter Weather Advisories have been put into effect throughout the western U.S. Meteorologist Star Harvey spoke with meteorologist Adam Epstein for more details.

Here’s a look…