A storm system that could trigger flash flooding and flows of mud and debris took aim at the region Wednesday, promising rainfall in the Los Angeles area starting Friday, forecasters said.
The approaching system, which originated in the northern Pacific, remained over the eastern Pacific Wednesday and was forecast to make itself felt along the Central Coast Thursday before sliding into Ventura and Los Angeles counties early Friday, according to the National Weather Service.
The storm was projected to generate between 1 and 2 inches of rain in San Luis Obispo and Santa Barbara counties and up to an inch in Ventura and Los Angeles counties, although greater amounts are possible in the mountains — especially in Ventura County — and wherever thunderstorms develop, the NWS said.
The storm system is entraining moisture from Hurricane Seymour, which will translate into muggy weather Friday, said NWS meteorologist Robbie Munroe, adding that amid the warm conditions expected, the snow level will remain at a high 10,000 feet.
The approaching storm is expected to be wetter than the one that hit the region late Sunday and early Monday and  likely will produce gusty south-to- southwest winds, the NWS said, adding that it could lead to ponding on roadways, flash flooding and debris flows down slopes previously denuded by wildfire.
The San Gabriel Valley foothills around Duarte, Bradbury and Azusa have been weakened by years of drought and occasional brush fires, leaving the area prone to debris flows when rain comes down in short, heavy bursts, NWS forecasters said.
This week’s storms are the first of the fall rains in Southern California. The approaching storm will not have dramatic  impacts on temperatures, which will be a few degrees above normal in the valleys Wednesday but a couple degrees below normal in L.A. County’s coastal zone, Munroe said, adding that rainy Friday’s temperatures will generally be five degrees below normal.
Mostly sunny skies were forecast in Los Angeles County Wednesday, along with highs of 72 at LAX; 73 in Avalon; 75 on Mount Wilson; 78 in downtown L.A., San Gabriel and Long Beach; 79 in Burbank and Palmdale; 80 in Pasadena and Lancaster; 81 in Saugus; and 84 in Woodland Hills. Temperatures will rise slightly Thursday, hitting the low 80s in several communities, dip to the high 60s and low 70s Friday, when the forecast calls for rain, rise to the mid 70s Saturday, then fall to the high 60s and low 70s Sunday.
Sunny skies were forecast in Orange County Wednesday, along with highs of 70 in San Clemente; 71 in Newport Beach; 72 in Laguna Beach; 77 in Anaheim, Irvine and Mission Viejo; and 79 in Fullerton and Yorba Linda. Orange County temperatures will rise slightly Thursday, hitting the low 80s in some communities, then decline to the mid 70s amid showers on Friday. Highs will remain in the mid 70s Saturday, then fall to the high 60s beginning Sunday.
