I recently sent out a Twitter update about this - the weather pattern is about to shift. The impacts will be minimal in Southern California, though the record-breaking heat will not return for the rest of the month. Instead, San Diego and surrounding areas will remain dry and seasonably mild through at least January 25.
However, the Pacific Northwest and Eastern U.S. will see some big changes. A persistent ridge (highlighted below) has been the dominant feature over the past three weeks for San Diego and all of California. This has kept the entire state hot and extremely dry.
There are signs of this warmer air starting to pool around the Gulf of Alaska (marked on the map below). This is the start of the pattern shift.
This powerful blocking ridge shifts west and allows a persistent upper-level low to develop over the Pacific Northwest next week. Northern California desperately needs rain, so this could be great news!
By the end of this forecast cycle, the ECMWF ensemble shows a blocking ridge developing near southwest Greenland (shown below). This is a loooong way away, but it is worth watching if you live along the East Coast. Big snow storms typically develop in late January and early February for the Mid-Atlantic and New England. This pattern could potentially be favorable for one or two threats for some snow.