Some showers moved into California this week, but a much more impressive and widespread round of rain is set to move into the state starting this Monday. This is all thanks to the breakdown of the ridge of high pressure over the western US, allowing for storms and moisture to move further south into the West Coast instead of just the Pacific Northwest. Currently we are watching a weak area of low pressure developing this weekend. To the north, a piece of energy associated with a stalled boundary will begin to pick up the low pressure and move toward Northern California. By the time Monday arrives, that storm will near the coast. Because this storm will stall just off the coast of California on Monday, days and days of rain is thankfully in the forecast. I mention “thankfully,” because the southern half of the state has been drying up, with many parts of it feeling the affects of a drought.
On Monday, rain will begin to work into much of the California coast during the morning. This includes San Fransisco, but Southern California will remain dry. However, that will change in the afternoon, when a widespread moderate rain spreads into all of the state. There will even be much-needed snow for much of the Sierra Nevada. During the overnight hours of Monday, there won’t really be any changes to the weather across all of California.
Tuesday will again be a rainy day across the state. Rainfall intensity will taper off as the day progresses. The snow will be going strong in the Sierra, with snow accumulations continuing. There is also the chance for a bit of snow during the afternoon for the San Gabriel Mountains. We are concerned that with all this rain headed to an extremely dry Southern California, there will be mudslides, especially where the burn scars are following the massive wildfires the past several months. During the night Tuesday, the rain will clear out of Northern California while it continues for the southern half of the state. The snow will also taper from north to south in the Sierra.
During the day on Wednesday, high pressure will gradually begin to move in as the rain departs, however, a few lingering rain showers are possible near the Oregon/California border.
Through Wednesday, a widespread three to five feet of snow is forecast for the Sierra Nevada. For the rest of the state where rain is forecast, most locations are expected to receive one to two inches of rainfall through Wednesday. Even though our map doesn’t reflect this, portions of Southern California in the Los Angeles area may receive up to six to twelve inches of rainfall in the higher elevations.