Late summer storm hovers off SoCal coast

The unseasonably deep cutoff low that brought thunderstorms to parts of the Coastal Range and the Sacramento Valley yesterday and light rain to the Bay Area this morning is  currently spinning about 400 nautical miles off the CA coastline. The majority of precipitation associated with the low remains offshore at this time, though a few showers have recently developed along the immediate CentCal coast and over the Sierras. Expect that shower coverage will slowly increase overnight into Friday across the southern half of the state as the low begins to lift slowly NE. The cutoff, which has been rather starved for moisture as of yet, will begin to moisten as it spends time over the Pacific Ocean. As a result, some heavy  precipitation is still possible over the south facing coastal slopes in CentCal/SoCal as well as anywhere isolated thunderstorms occur. Heavy snowfall of up to 12 inches is possible in the Sierras and to a lesser degree in the SoCal mountains. Would expect that 80% of locations south of Santa Barbara will see at least 0.10 in. with this system. As the low lifts northeastward late Friday into Saturday morning, the precipitation shield will lift north once again with renewed rain chances for the Bay Area and Sacramento Valley. Convective activity is still possible at any time, mainly over SoCal. There is some uncertainty as to the nature of the precipitation over NorCal on Saturday–it looks rather convective on model output, so some thunderstorms may be possible then if there are any sunny breaks. I think it’s too early to write this one off just yet, and the models actually did a pretty admirable job modeling this system (esp. the GFS) quite a few days out. Stay tuned.