Light rain made for a damp commute in many parts of the Southland Tuesday, but a more powerful storm was bearing down on the region, again raising fears of flooding and debris flows in recent burn areas.
Tuesday evening is expected to be mostly dry, although some showers are still possible in some mountain areas, according to the National Weather Service.
But the situation will change dramatically Wednesday as a storm front pushes over the area, bringing “heavy rain and strong winds” to the region.
Rain will start lightly in the morning with precipitation falling at rates ranging from one-tenth to a quarter-inch per hour in some areas. But by Wednesday afternoon, the rain will increase steadily, with downpours continuing into Thursday and reaching an inch per hour in some locations. The “peak intensity” of the storm is expected to be Thursday morning.
NWS forecasters said 2 to 4 inches of rain could fall across most of the area, with some mountain areas receiving 4 to 8 inches.
“These rates and amounts could cause significant flash flooding or debris flows across the region in and outside of recent burn scars with significant small stream and urban flooding possible,” according to the NWS.
The NWS issued a flood watch that will be in effect Wednesday evening through Thursday afternoon over the bulk of the Southland. In Orange County, the flood watch will be in effect Thursday morning through Thursday afternoon.
The rain will be accompanied by gusting winds. A wind advisory will be in effect in Orange County from 2 a.m. to 4 p.m. Thursday, with winds of 15 to 25 mph possible, including gusts of up to 40 mph, according to the NWS.
Forecasters said wind watches could be issued in Los Angeles County mountains and deserts as the storm develops.
“There will be many potential problems associated with this storm system including urban and small stream flooding, rocks and debris on roads, downed trees and numerous power outages, and mud and debris flows out of recent burn areas,” according to the NWS.
Conditions are expected to dry out by Thursday night, continuing into Friday. A series of “weak disturbances” are anticipated over the weekend, but “there will likely be drier and less cloudy intervals in between the clouds and rain,” forecasters said.
Temperatures, meanwhile, will remain about six degrees cooler than normal through the weekend.
With rain falling, Los Angeles County health officials issued their standard warning for people to avoid entering ocean water near discharging storm drains, creeks and rivers. An ocean water quality rain advisory will be in effect until at least 7 a.m. Friday.
Health officials noted that stormwater runoff that reaches the ocean can carry bacteria, chemicals, debris trash and other health hazards. People who come in contact with impacted water in the ocean could become ill, health officials said.