The cold storm sitting off the Northwest coast has brought the first significant snow of the season from the Washington Cascades south into the central Sierra of California. This storm will continue to sit off the coast through tomorrow before moving east on Wednesday. The afternoon satellite picture shows a lot of cellular looking clouds over the Northwest and offshore and also a cold front that was in central California.
Snow fell in the Northwest this weekend and today and then also into the northern and central sections of the Sierra today. From the National Snow Analysis, here is the snow depth as of Monday morning.
More snow will fall at just about any time through Wednesday in the Cascades with another round of pretty good precipitation Tuesday into Tuesday night. Farther south, the moderately heavy snow of today will taper tonight to only a few snow showers tomorrow. But then a period of more important snow will come back in Tuesday night into part of Wednesday.
Additional snow accumulations are likely to be in the 6- to 12-inch range with locally higher amounts of 1 to 2 feet. The greatest snow accumulations are likely to be in the Oregon Cascades and in the Sierra down to south of Tahoe. Travel in and through the mountains will continue to be locally hazardous and, if you are planning on heading through these areas, chains will either be a must or at least a very good idea.
These is the possibility that another surge of tropical moisture could move into Arizona and Southern California by the middle of next week.
I still believe the greatest amount of rain, at least partially relating to Norbert, occurs from southeast California to Arizona
The effects on Southern California are very much in question.
With low wind shear and warm water in its path for a while longer, it is likely that Norbert intensifies into at least a Category 2 storm.
For much of the last week the monsoon moisture flow into the Southwest has been completely shut down by dry westerly winds. This is about to change.
A big pattern change is underway, one that will completely shut down any chance of showers and thunderstorms for an extended time period.