Two storms will strike Southern California starting Wednesday, with the more significant of the two expected to arrive Friday and generate a "very impressive" volume of rain, forecasters said.
"A dramatic change in the weather is expected the second half the week as a couple of winter storms are forecast to move across southwestern California," according to a National Weather Service advisory.
Southern California's rainfall will start in San Luis Obispo and Santa Barbara counties Wednesday afternoon, then spread south into Ventura and Los Angeles counties that evening, leaving the region Thursday morning, with a threat of showers lingering in the mountains through Thursday afternoon, NWS forecasters said.
That storm is expected to generate a quarter-inch of rain or less, perhaps more in some "upslope" areas and gusty south-to southwest winds, they said. The snow level will remain at a high 7,000 feet Wednesday, dropping to 6,000 feet Wednesday night and Thursday.
"The second storm will impact the area Friday and Saturday and will likely be the strongest storm the area has experienced in quite some time," according to the NWS advisory.
The rain will start in San Luis Obispo and Santa Barbara counties Friday morning and hit Ventura and Los Angeles counties that afternoon, exiting Saturday morning but leaving in its wake shower activity through Saturday, said the NWS advisory.
"Rainfall amounts could be very impressive," it said, citing early projections of between 1 and 2 inches along the coast and in the valleys and between 2 and 4 inches in the mountains and the foothills, with the greatest rainfall expected along south-facing slopes.
Conditions accompanying the second of this week's storms "could be favorable for thunderstorm development, which would bring heavy rainfall over a short time period," according to the advisory.
The snow level Friday generally will be above 7,000 feet but drop to around 5,000 feet by Saturday, it said, adding that "The mountains could receive some significant snowfall and winter storm conditions due to strong and gusty south-to-southwest winds."
The NWS said that in light of "the potential for heavy and intense rainfall," it is particularly concerned that the second of this week's storms will trigger mud and debris flows in areas denuded by wildfire, including the 1,952-acre Colby Fire in the hills above Glendora and Azusa in January and the 28,000-acre Springs Fire in Ventura County in May.
Amid partly cloudy skies, Southland highs will be in the 60s and low 70s today and Tuesday, then fall to the 60s over the rest of the week. By Sunday, some areas will have temperatures highs 10 degrees lower than today.
"The rain will help a lot" but not enough to rescind the declaration of a drought, said NWS meteorologist Kathy Hoxsie, adding that this winter has been one of the driest on record in California so far and temperatures in the past three months have been above normal.
Several record highs have been set in the region recently, including on Sunday in the Antelope Valley at Sandberg, where the high was 69 degrees, topping the record of 68 set for a February 23 in 1995, according to the NWS.
The second of this week's storms is expected to be the Southland's wettest since March 25-26, 2012, and downtown L.A. is expected to get more rain than at any time since around an inch was recorded Oct. 5 2011, she said.
– City News Service.