The National Weather Service said a low-pressure system sliding south along the coast of California is set to bring widespread rain and possible thunderstorms to Southern California between Wednesday and Thursday, with some areas expected to receive up to 5 centimeters of rain. The first traditional storm system of the season is still taking shape, but forecasters said rain could begin as early as Tuesday night and continue into Thursday before tapering off in Los Angeles County late Thursday or shortly after.
The timing matters because residents in Los Angeles County and Orange County are now looking at a sharp change after several days of unusual heat and strong Santa Ana winds. Temperatures began falling over the weekend as sea breezes weakened, and further cooling was expected Monday and Tuesday before the rain arrives. In Los Angeles County, afternoon highs were expected to settle around 70 degrees, with Wednesday and Thursday cloudy and cool across much of the area.
In the Los Angeles area, Wednesday is expected to bring mainly light rain before showers become more convective overnight Wednesday into Thursday. The storm is expected to deliver about 12 hours of rain, and Los Angeles County could see between three-quarters of an inch and 1 inch, while the foothills and coastal mountain slopes could get 2 inches. There is also a 25% chance that rainfall will exceed those amounts, and the National Weather Service said there is a slight chance of thunderstorms.
That is the part forecasters are watching closely. Dangerous rainfall is not generally expected unless thunderstorms develop, but the latest forecast also points to lighter precipitation on Wednesday before showers become more widespread overnight Thursday into Friday. In Orange County, showers and a slight chance of thunderstorms are forecast as well, with the highest chance of precipitation between Wednesday night and Thursday morning. Coastal highs there are expected to be between 70 and 75 degrees on Wednesday, then fall to between 60 and 70 degrees on Thursday.
The next shift to watch is not whether rain arrives, but how quickly the forecast settles on the exact timing. The National Weather Service still sees the best chance for the season's first traditional storm system between Wednesday and Thursday, yet the rain could start Tuesday night and the heaviest pockets may depend on whether thunderstorms form over Los Angeles County and Orange County.
