While the weather in the East quiets down over the next several days, the west coast from northern California to the Pacific Northwest will be pummeled by a series of frontal systems and Pacific Ocean storms and, unfortunately, the atmosphere is setting up in such a way that the rainfall in northern California, and perhaps southwest Oregon, could be historic. A deep upper level trough will set up shop in the eastern Pacific Ocean for a few days and this will open the flood gates for a moisture plume to develop extending all the way from the Hawaiian Islands to the US west coast and major flooding could be the result. The soaking begins today as the initial system barrels into the west coast, but this will be a rather quick mover and a relatively “conventional” storm. The next system rolls ashore on Thursday and this will have the extreme moisture associated with it that will have its origins over the Hawaiian Islands. More rain will follow that storm on Friday and the threat will continue daily right through the weekend. By the time all is said and done, more than a foot of rain could fall across northern California, and perhaps southwest Oregon, over the next 5 days or so with the high potential for flash flooding, rock/mudslides, etc.
Rainfall amounts in southern California will be much lighter over the next few days, but not insignificant. This atmospheric set up will also produce heavy snow of more than a foot over the high elevation Sierra Mountains and also the Bitterroots, Tetons, Wasatch and Washington Cascades. Also, this pattern will send a plume of mild air eastward across the country that will first warm up the central Rockies later this week, then the Plains significantly this weekend, and then the eastern states early next week.