An upper level low is dropping into the Martin Storm Diamond tomorrow (Sunday) and the risk of shower and thunderstorm activity increases in the metros so read on for details.
The risk of shower and thunderstorm activity will be on the increase for Sunday as an upper level low drops southwest of the region, landing Southwest California in the area of upper divergence. Mid-level moisture will be present along with an easterly flow around the northeast periphery of the upper level low. Areas from Ventura and Santa Barbara County, including Vandenberg Air Force Base, will have the best chance at solid precipitation from this event.
The flow, out of the southeast, for Los Angeles, Orange, San Diego, and the Inland Empire areas will make it possible for activity in the Inland Empire areas but drier air is making me concerned this is a non-event for the most part for you.
On Monday the flow shifts back south-southwest to north-northeast with the departing system and this is when the High Desert and Morongo Basin get hit the hardest ..