After a dry, tranquil day Tuesday, a cold, soggy guest will muscle its way into Southern California’s holiday plans late that night.

A deep upper-level trough of low pressure is forecast to develop over the West Coast and bring cold, wet conditions to the region from Wednesday through at least Friday, according to the National Weather Service. The system is carrying sufficient moisture to bring moderate to locally heavy precipitation and, with the cold air aloft, may generate isolated thunderstorms.