Strong winds and up to six inches of rain on some mountain slopes were lined up to hit the Southland, forecasters said Sunday, as the driest 10-month period in 140 years in downtown Los Angeles looked certain to be drowned by a two-day soaker.
Computer models have changed, according to the National Weather Service, and both the preliminary warm storm Monday and big cold storm on Tuesday will both be wetter than first thought.
Light rain may hit Southland freeways for the Monday morning commute, with 1/4 inch of rain possible by sunset Monday on the flatlands, and 1 inch in the mountains.
Winds of up to 60 miles an hour may hit the Antelope Valley, the Grapevine and the Central Coast on Monday, the NWS warned.
By Monday afternoon, snow will start falling above 8,000 foot elevations, dropping to 6,000 feet by Tuesday afternoon and 4,000 feet by Tuesday evening, as the vigorous cold front arrives from the Gulf of Alaska and collides with the wet warm front already soaking the Southland.
The Interstate 5 pass at the Grapevine could see light snow accumulations and icy conditions starting late Tuesday afternoon.
In the flatlands, some south-facing slopes — such as the Thomas Fire burn area — are forecast to receive 5 to 6 inches of rain Tuesday. Rain may fall at the rate of 1 inch per hour, as the collision of warm and cold air might spark thunderstorms, forecasters warned.
NWS Meteorologist Joe Sirad told City News Service the flatlands of L.A. County will get the most rain since last Feb. 17, when downtown L.A. got 2.01 inches.
“Our confidence is quite high,” Sirad said of the computer models aiding in the forecast.
In 2017, downtown Los Angeles experienced its driest March 1 through Dec. 31 since 1878, with only .69 of an inch of rainfall, he said.
The expected moisture may be welcome for some residents, but not those who live in the Creek, La Tuna, Rye and Skriball burn areas, where there is a “strong potential for mud and debris flows,” Sirad said.
“People in burn areas need to take protective measures and listen for evacuation messages,” Sirad said.
It also could result in urban street and underpass flooding making for a “rainy, windy commute” on Tuesday, he said.
An offshore flow is forecast to return late Wednesday with warmer temperatures, dry air, low humidity and gusty winds through Sunday. Saturday may see sunny skies and highs above 80.
But more rain could arrive around the following Monday, Jan. 15, Sirad said.