The first in an expected series of four storms dropped light rain on the Southland today ahead of a much stronger system, which will arrive Tuesday and threaten to unleash torrents of mud and debris over slopes denuded by wildfire, forecasters said.
In all, there will be four storms this week — Tuesday, Wednesday and Thursday, according to the National Weather Service. Forecasters say they are part of the El Nino effect, resulting from a warming of Pacific waters.
NWS meteorologist Curt Kaplan said today’s storm should produce "nothing terrific" but on Tuesday, "we can anticipate debris flows and high surf" as each of this week’s storm will be forming its own swell.
Rainfall totals through today are expected to be between a 10th and a third of an inch. An inch or two of snow may fall above 6,000 feet.
Tuesday’s storm could bring an average of two inches of rain in coastal and valley areas, and two to four inches in the foothills and mountains. Rainfall totals could exceed a half-inch an hour over recent burn areas, including the site of the Solimar Fire in Ventura County.
That much rain in a short period could bring flooding and debris flows, and residents near the sites of previous wildfires were urged to monitor weather reports and prepare sandbags.
"Residents … especially those living in or below recent burn areas, should prepare now for the impending heavier rainfall this week," an NWS statement said.
In Glendora, police announced that the alert for residents in the area below the Colby Fire site has been raised to yellow, meaning street parking is restricted and roadways must be cleared. In Azusa, officials were handing out sandbags.
The NWS warned that Tuesday’s storm could trigger flash flooding.
Also forecast this week is about 2 feet of new snow in the mountains above 6,000 feet this week. Snow levels will generally be between 5,000 and 6,000 feet, but could get as low as 3,500 feet Wednesday through Friday, according to the NWS. The snow could cause hazardous driving conditions next week in the mountain areas and across The Grapevine.
Coastal areas can expect high surf throughout much of next week and possible flooding, especially during the middle of the week when a large swell arrives, according to the NWS. Western-facing beaches will be particularly vulnerable to flooding on Tuesday and Wednesday.
A high surf advisory will be in effect in Los Angeles County until 10 p.m. Thursday. In Orange County, a high surf advisory will go into effect at 4 p.m. today, lasting until 10 p.m. Friday.
"The overall pattern that is bringing us these storms is finally looking like what we would expect the El Nino pattern to look like that it so far hasn’t this summer," said John Dumas, science and operations officer for the NWS.
The NWS forecast showers today and temperatures in the 60s. In Los Angeles County, the NWS forecast highs of 49 on Mount Wilson; 54 in Palmdale and Lancaster; 56 in Saugus; 60 in Burbank; 62 in Pasadena and San Gabriel; and 64 in Avalon, Long Beach, downtown L.A. and at LAX. In Orange County, the NWS forecast highs of 62 in Newport Beach, Laguna Beach and San Clemente; 63 in Irvine and Mission Viejo; 64 in Yorba Linda; and 65 in Anaheim and Fullerton.
Tuesday’s highs under rainy skies are expected to be 4-5 degrees lower than today.