Update from Dave Hovde 9:40pm
The main band of rain is now in SoCal however more on and off showers are likely into Friday afternoon. Here is a look at the storm total rain thus far, we'll put the rain in more perspective on Friday: (the Flood Advisory in Santa Barbara County has been dropped)
Update from Dave Hovde 6:10pm
A new flood advisory was just issued for the Southcoast and hills. 1-4" of rain with more on the way is producing areas of ponding and flooding and caution is advised. Flood concerns for the Alisal Fire burn scar are in play where minor flows are not out of the question.
A large and slow-moving system is still dragging across the Central Coast and California. This system had a lot going for it: sub-tropical moisture supply, low pressure, southerly winds, surface, and upper-level low pressure, and a favorable jet stream pattern.
There is still more of this system yet to move thru the area into Friday morning.
The cold front and upper low still have to transition from over the water to the east which will keep rain going. The main band is sliding into SoCal but cooler unstable air is moving in associated with the front and the trough.
So far the Central Coast has seen 1 to 6+" of rain with the highest amounts in the hills.
Widespread areas of standing water, runoff, and flooding did prompt flood advisories but not flash flooding since it has been a steady rain rather than fast and very hard in terms of rain rates. The new unstable showery sector of the system could provide brief heavier downpours and thunderstorms can't be ruled out into Friday afternoon.
A brief break later Friday but a showery system Saturday is likely with another showery system Monday, I think these are .50" or less systems other than higher elevations which could see up to 1".
Snow levels will be much lower, generally 5000` for most of the event but then dropping to as low as 3000` Sunday morning.
Precip will be tapering off quickly Sunday morning but light snow accumulations are possible down to 3000` especially north-facing slopes that could continue into early afternoon. So this could present some issues for the Grapevine Sunday for people driving through there the day after Christmas.
Another cold and fast-moving system will drop out of the north Monday and bring more showers and low elevation snow lingering into Tuesday. Looks similar to the Saturday system.
After Monday the forecast looks active but models are really struggling on consistent details. Right now I'm broad brushing Wed-Friday for more rain. Right now the GFS model has a huge NYE-NYD storm but on other runs it is either weaker or not really there. Please stay in touch with the forecast for refinement in the extended forecast.