LOS ANGELES -- Heavy rain struck the Southland Monday morning amid thunderstorms, lightning and thunder, causing some roadside flooding, on the eve of what is expected to be a sharp warming trend.
What appeared to be the main band of precipitation from a new storm reached the Los Angeles Basin after 6 a.m. and appeared to have moved east by 9 a.m. But some precipitation was expected at least until early afternoon, National Weather Service forecasters said.
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The NWS warned the storm will have cold air behind it, an instability factor that could trigger scattered heavy rain and thunderstorms.
This morning's first significant rainfall, punctuated by lightning strikes and thunderclaps, caused minor flooding at some intersections, prompting motorists to gingerly drive around areas where water had pooled.
Heavy snow could fall down to the 5,000-foot level today, and snow could fall on major freeway passes at The Grapevine and Cajon Pass tonight and Tuesday morning, according to forecasters.
There was good news from the City of Los Angeles' watershed in the headwaters of the Owens River near Bishop. An estimated two feet of snow fell Sunday at Mammoth Lake, above the Los Angeles Aqueduct.
The rain from an earlier storm ending before dawn Sunday was heavy and constant in the Santa Monica Mountains. A fire station in Malibu Canyon got 2.71 inches of rain overnight, and the Malibu Civic Center got 1.3 inches.
Bel Air saw 1.65 inches, 1.22 inches fell at Century City and 1.57 inches dropped on Sherman Oaks. Los Angeles firefighters activated swiftwater rescue crews to evacuate a cluster of homeless people from the flood plain upstream of the Sepulveda Basin dam, but police did not close roadways.
The official downtown rain gauge at USC got .73 inches, Santa Ana saw .29 inches, and .48 fell at Villa Park in northeastern Orange County. Rainfall amounts in the San Gabriel Mountains were less than near the coast: 1.5 inches at Santa Anita Canyon.
The California Highway Patrol handled 150 collisions between 10 p.m. Saturday and 4 a.m. Sunday as the first of two storms left behind rain-slickened streets throughout the Southland. That's compared with 65 collisions during the same time frame last weekend, the CHP said.
Drier weather was expected Tuesday, the NWS said.
The NWS forecast highs today of 44 on Mount Wilson; 52 in Palmdale and Lancaster; 58 in Mission Viejo; 59 in Avalon, Newport Beach, Laguna Beach and San Clemente; 60 in Yorba Linda, Irvine and Fullerton; 61 in Saugus, Burbank, at LAX and Anaheim; and 62 in Woodland Hills, Pasadena, San Gabriel, Long Beach and downtown L.A..
A warming trend is expected beginning Tuesday, when temperatures are expected to rise sharply -- 12 degrees in some communities -- amid sunny weather. A retreat to the high 60s is expected Friday.