A storm system out of the Gulf of Alaska will strike the Southland this weekend amid a sharp drop in temperatures, but its intensity is not yet certain, forecasters said Friday.
The system will manifest itself in two stages, National Weather Service meteorologist Dave Bruno said in a telephone interview from his observation station in Oxnard. The first wave of rain will arrive Saturday night and likely be over by midnight, he said, with a second wave expected late Sunday morning in the form of showers.
How much rain the approaching system will generate was uncertain this morning, although Bruno said the volume was expected to be “not too heavy” — between a quarter-inch and three-quarters of an inch of rain generally but possibly more than an inch in the foothills.
It was not yet possible to say this morning if the rain would trigger mud and debris flows down slopes previously denuded of vegetation in wildfires, Bruno said, adding that such an outcome is possible if thunderstorms develop Saturday night.
The storm may cause the snow level to drop to 4,500 feet, Bruno said. That could result in snowfall on Interstate 5 in the area of The Grapevine, he said.
With the storm’s arrival, temperatures will drop sharply — between 10 and 13 degrees throughout Los Angeles and Orange counties. Downtown L.A, for example, will go from a forecast high of 77 degrees Fahrenheit Friday to 66 amid rain on Saturday, while Saugus goes from 75 to 62.
Temperatures will fall another 6 degrees or so on Sunday. Sunny weather will reappear Monday but temperatures will remain in the 60s as a mild warming trend gets underway.
In the meantime, the NWS forecast sunny skies in L.A. County Friday and highs of 61 in Palmdale and Lancaster; 71 on Mount Wilson; 73 in Avalon; 75 at LAX and in Saugus; 76 in Long Beach; 77 in San Gabriel and Burbank; 79 in Pasadena; and 80 in Woodland Hills.
Sunny skies were also forecast for Orange County Friday, along with highs of 71 in Laguna Beach and San Clemente; 72 in Newport Beach; 75 in Mission Viejo; 76 in Irvine; 78 in Yorba Linda and Anaheim; and 79 in Fullerton.
