The NOAA Automated Atmospheric River Detection system has picked up a storm with some potential in the Pacific, which at this point (five days out) seems to be pointed at California:

Atmospheric River?

That’s the forecast image for Monday morning. According to Michael Dettinger, who was fielding my questions this afternoon on Twitter, AR storms are very unusual this time of year. It’s definitely the unrainy season there, with Sacramento averaging just 0.18 inch of rain in June. The Sacramento NWS office has more. (Also thanks to Matt Weiser at the Sacramento Bee for pointers.)