The first in a series of three storms expected to douse the Southland is expected to arrive late Wednesday evening, bringing another barrage of rain expected to last through the weekend and again raising fears of mudslides in recent burn areas.
According to the National Weather Service, clouds will likely increase over the area Wednesday night, with rain starting to fall primarily north of Los Angeles County before moving across the Southland Thursday.
“Rain will continue much of Thursday, with only some showers across the southern portions (of the area) by late (Thursday) afternoon and evening,” according to the NWS.
Rainfall totals on Thursday are expected to range from a quarter-inch to three-quarters of an inch, although some foothill and mountain areas could get an inch — with rainfall increasing if the “slight chance” of thunderstorms develops.
The best chance of thunderstorms will be Thursday afternoon, according to the NWS.
The rain is expected to dissipate Thursday night, other than some lingering showers, giving way to partly to mostly cloudy skies Friday morning. Forecasters said Thursday’s rain could create some shallow mud and debris flows in the recent Woolsey and Hill fire burn areas.
A flash flood watch will be in effect Thursday morning and afternoon in the Santa Ana Mountains and foothills and the Holy Fire burn scar in Orange County. With the impending rain, the Orange County Sheriff’s Department on Wednesday issued a voluntary evacuation order for the Trabuco Creek, Rose Canyon, Mystic Oaks and El Cariso areas, effective immediately.
Sheriff’s officials urged residents to leave the area before the rain begins, noting that evacuation routes can quickly become flooded. People with large animals were also urged to consider moving them from the area in advance of the storm.
By Friday night, a more powerful storm will arrive, with rain beginning in Santa Barbara and Ventura counties around midnight Friday night, and Los Angeles County likely getting doused beginning before dawn Saturday morning.
Rainfall rates of 0.5- to 0.8-inch per hour are expected, although some localized downpours could bring rain rates of an inch per hour, again creating the risk of mudflows in burn areas. Rainfall totals of 1.5 to 3 inches are expected in the storm, with up to 4 inches possible in south-facing slopes, according to the NWS.
The storm will be accompanied by windy conditions, including some gusts of more than 65 mph in higher-terrain areas, forecasters said.
According to the NWS, the rain will again taper off Saturday night, with the third storm expected to move in late Sunday into Monday. Forecasters said the third system appears to be much weaker, with the best chance of rain coming Monday.
Clear weather is expected beginning Tuesday, but there is a chance of another storm system moving in by the following weekend.