This winter, we've already had two occurrences of storms caused by cut-off low pressure systems, where an area of low pressure becomes detached from the Jet Stream and meanders around, often for several days, spinning and (when moisture is available) sending multiple bands of clouds and precipitation onto shore. Forecasters have a hard time predicting the creation and behavior of these cut-off lows, as weather forecasting models often produce conflicting results (as they do with other self-contained weather events, like hurricanes).
The current cut-off low was not forecast at all as recently as late last week, and over the weekend it was predicted to bring showers on Tuesday (under a quarter of an inch) and slightly heavier rain (up to half an inch) today. In fact, we've received over three inches so far from this storm, with no sign of letup. Now, the forecast suggests that we'll see bands of precipitation all week, and then maybe a substantial storm as we get to early next week. It's been wonderful, gentle rain so far, with hardly any wind and a moderate pace that has allowed it all to soak in. In a sign that we're finally replenishing our ground water, Tablas Creek is running noisily away.
A good shot of the current conditions, showing the band of north-south precipitation that has been flowing north over the Paso Robles area for the last 36 hours, from the National Weather Service: