The long-anticipated pattern change is currently at our doorstep. The persistent West Coast ridge is finally being undercut by the subtropical jet stream, and a line of storms are queuing up over the Pacific. The first…and weakest…system will roll into NorCal on Wednesday, bringing brief heavy rains and wind gusts to 35 mph. SoCal could see a few showers, but no sig. precip. with this storm. A much stronger…moister…and larger storm system will deepen as it approaches the coast on Thursday. This storm appears to have a strong moisture tap to the subtropics, and has the potential to bring heavy rains and strong winds to NorCal and CentCal. SoCal should see some rain out of this event, but there will be a definite N-S rainfall gradient (San Diego may see very little). Warm advection processes could generate 6-12 hours of rain ahead of the main cold front. This rain could be heavy at times, with accumulations of 1-3 inches possible in the wetter areas of NorCal. Late Thursday night and Friday, the strong cold frontal band will move rather slowly through California, producing 2-4 hours (at least) of heavy rain and strong winds gusting over 50 mph. Rainfall after the warm advection could easily total an additional 1-3 inches in many places, resulting in a storm total of 2-6 inches by late Friday (in addition to the 0.5-1.5 inches that will fall on Wednesday). Keep in mind that the vast majority of this rain will fall in NorCal. Some more rain…possibly heavy at times as the subtropical tap will remain focused over CA…will continue through the weekend. An additional 1-3 inches could potentially fall on Saturday and Sunday. Rainfall of this magnitude would do wonders to ease (erase?) the rainfall defecit in the north (though snow levels will be very high–above 8000 feet), but SoCal’s share of the rain remains to be seen. Stay tuned, as the forecast may change over the next few days…