The first major storm of the season is expected to bring significant rainfall and lightning to Southern California starting late Tuesday night.
In addition to heavy precipitation, the storm has the potential to bring snow to mountain areas as temperatures drop 30 to 40 degrees by Wednesday, according to National Weather Service meteorologist Alex Tardy.
The storm system represents a dramatic weather shift for the Southland, which only this past weekend saw record daily high temperatures in areas including downtown L.A., Long Beach and Camarillo.
“We’re going to see some drastic changes to our weather starting to unfold now,” Tardy said.
He noted that the last time the area received significant rain was in September, while the last “winter storm” to hit the area was back in May.
Rainfall totals of one-half inch to 1 1/2 inches are possible in most locations, Tardy said. Some areas could be drenched with 2 inches locally, with rates of up to 0.6 inches per hour.
San Diego County is forecast to receive the heaviest rain, with widespread amounts of 1 to 2 inches, Tardy said.
Los Angeles County could be inundated with three-quarters of an inch of precipitation, according to the NWS forecast.
Showers and thunderstorms were expected to develop over the area as early as Tuesday afternoon, with the heaviest rainfall expected Wednesday, the weather service stated.
Light showers were falling across much of the Southland by late Tuesday, though the full brunt of the storm had yet to materialize. NWS in San Diego said more than an inch of rain had only fallen in a few areas by 5 p.m., and NWS in Los Angeles said light precipitation was scattered from Redondo Beach to Pasadena.
Forecasters warned of potential impacts such as slick roadways that may impact traffic, road closures due to flooding, and mud and debris flows in recent burn areas.
The main storm will be followed by more showers between Wednesday night and Thursday.
Mountain areas, meanwhile, will see significant snowfall above 6,000 feet, with some areas receiving 4 to 8 inches. Elevations above 7,500 feet could get up to 10 inches.
Snow is most likely on Wednesday, when temperatures are expected to plummet, Tardy said. The chilly weather will continue through the end of the work week.
A cold weather alert has been issued for parts of L.A. County, including mountain areas on Wednesday and in the Antelope Valley on Saturday.
The county's Department of Public Health warned residents and those in the affected areas that wind-chill temperatures are expected to dip below 32 degrees.
“Children, the elderly, and people with disabilities or special medical needs are especially vulnerable during cold weather. Extra precaution should be taken to ensure they don’t get too cold when they are outside,” L.A. County Health Officer Muntu Davis said in a news release.
Davis urged people with limited access to heat to visit shelters or other public facilities, such as malls, libraries or senior centers.
"We also want to remind people not to use stoves, barbecues or ovens to heat their homes due to the risk of carbon monoxide poisoning," he said.