Monday 4am to Tuesday 4am The yellow area has a moderate risk of flash flooding while the red area has a higher risk. This includes Interstate 80 between Sacramento and Reno.  Tuesday 4am to Wednesday 4am Yellow indicates a moderate risk of flash flooding as the rain threat shifts south.  Wednesday 4am to Thursdays (Christmas) 4am We have a high risk of flash flooding over much of Southern California as heavy to near record rains are forecast to fall. It is unfortunate that "go kits" will be necessary for the Christmas holiday if you live in the red area.  Of course, I'll have additional updates tomorrow. 

6:15pm. All of the information below still looks valid, so I'm going to leave it up for the night.  I have a busy morning tomorrow, but hope to have something up by late morning, California time. Please check back.  Below are the forecast snow amounts in the Sierra from now until 4pm Sunday.  As much as 40 inches are forecast to fall. Most of the storm will fall on Sunday and the heavy snow will continue Tuesday and, possibly, Wednesday.  The flash flood threat will be high Sunday. ...and, Monday.  Please scroll down to see preparation suggestions.  [10:35am PST Update] New data indicates thunderstorms are nearly certain with storm #2 over parts of Los Angeles, Ventura and Santa Barbara counties. The updated rainfall amount forecast is calling for more than ten inches in the higher elevations of Santa Barbara county and right at ten inches in Los Angeles county!   I cannot overemphasize the importance of pre-planning. Create a "go kit" where you have ...