These are the National Weather Service’s forecast precipitation amounts through 4am Thursday morning. Click for larger image. Even more rain is forecast to fall through at least the 26th. Parts of Arizona could receive eight inches or more of rain before it is over. In addition, high winds and, in Southern California, isolated tornadoes are possible. Extremely heavy snows may occur over the mountains.
AccuWeather says California storms to be unrelenting. I urge readers in California and Arizona to be focused on the weather over the next ten days.
UPDATE I, 2:23pm Saturday: Ken Clark at AccuWeather has more details here.