A much-anticipated December storm moved into the Southern California region on Monday night, bringing rain and snow to the region.
By Tuesday afternoon, the City of Monrovia declared a local emergency after “significant” mud and debris flows. In Monrovia Canyon Park, debris flow caused damage to roads, parking areas, and trails.
Rain was already drizzling over parts of Ventura and Los Angeles Counties as of 11 p.m. Monday, and moved into the Inland Empire and Orange County by 5:15 a.m. on Tuesday.
Widespread, heavier rain will continue to move in as the first band of the storm moves into our area. The heaviest rain started around 6 a.m., and several hours of heavy rain are expected, continuing through the middle of the day.
The rain will taper in the second half of the day, as snow continues in the mountains.
The storm is expected to bring a total of 1-3″ of precipitation to the coast, basin and valleys, while the foothills and mountains are expected to see 3-4″ of water.
By 8:45 a.m., 1.34″ of rain had already fallen in Downtown LA, breaking the previous daily rainfall record of .96″ set in 1888. More rainfall records are expected to be broken.
Street flooding was already present in LA and Ventura counties at 5 a.m. Flood advisories are in effect until 7 p.m. in Ventura and 10 p.m. in LA county.
The LA River was up to 5 feet by 5:15 a.m., and up to nearly 7 feet by 7:39 a.m.
“This is a good indicator of the strength of the storm,” NBC4 meteorologist Belen De Leon said. “When you start to see this river level rise, that’s how you know that the storm means business.”
The Los Angeles International Airport announced around 1:53 p.m. that it experienced a brief power outage, but officials added that “systems are coming back online.” Power was restored by 2:13 p.m.
That announcement came after airports all around the region, including LAX, were forced to cancel flights due to inclement weather.
Cancelled Flight Update:

BUR – 67
SNA – 23
LAX, LGB, ONT – 2 flights each

Check flight status with your airline before heading to the airport…also check status if you were planning on picking someone up, we've had some flights divert to other airports.✈️ https://t.co/hkwli4Cmvz
As of noon, according to NBC4 meteorologist David Biggar, the cancelled flight totals at each airport stood at:
Because of the flooding during the rainfall, the Los Angeles County Department of Public Health issued a Beach Water Use Advisory on Tuesday at 12:45 p.m., effective until Friday, Dec. 17, at 7:30 a.m.
“Los Angeles County Health Officer, Muntu Davis, MD, MPH, is cautioning residents that bacteria, chemicals, debris, trash, and other public health hazards from city streets and mountain areas are likely to contaminate ocean waters at and around discharging storm drains, creeks, and rivers after a rainfall,” the statement read.
Those who enter the contaminated water could become sick.
A flash flood warning was issued for Orange County at 10:38 a.m., until 1:45 p.m.
FLASH FLOOD WARNING for portions of Orange County until 1:45PM

Rainfall gauges are indicating that flash flooding is occurring now or is going to begin shortly.

Do not drive through flooded areas. @NBCLA pic.twitter.com/tH8vkeoBnw
“Rainfall gauges are indicating that flash flooding is occurring now or is going to begin shortly,” Biggar said on Twitter. “Do not drive through flooded areas.”
Areas that may see flash flooding include:
A Flash Flood Warning has been issued for the Alisal burn scar region in Santa Barbara County.
Another Flash Flood Warning was issued in San Bernardino County, around the El Dorado and Apple Fire burn scars.
New FLASH FLOOD WARNING for portions of San Bernardino County, around the El Dorado and Apple Fire burn scars. The warning is up until 3:15PM.

There is a high risk of debris flows or flooding as heavier rainfall continues. pic.twitter.com/YtvJbI41Bx
That warning was in place until 3:15 p.m.
Debris flows are a possibility near burn scars from previous wildfires.
A mandatory evacuation was ordered for the Bond Fire burn area in Orange County, effective at 11:01 a.m., in effect until 12:30 p.m. Those in Silverado Canyon, Williams Canyon and Modjeska Canyon must evacuate “due to imminent debris flows along or near the burn scar,” the Orange County Sheriff said in a statement.
Evacuations were ordered in several San Bernardino County and Riverside County neighborhoods early on Tuesday, as rain was set to fall on burn scars from area wildfires.
Reports of rocks in the road on Highway 18 in San Bernardino County came through around 7:36 a.m. Rocks and debris were also reported on Highway 2 around 7:19 a.m.
At 11:01 a.m., there were reports of rocks as large as basketballs sliding into the road near Crestline in San Bernardino, near cross streets Lake Gregory Road and Horst Drive. Just under 2″ of water accumulated in the area in six hours.
The mountains could see 1-3′ of snow — that’s feet, not inches — above 7,000 feet. At 4,000 feet, there could be up to three inches of snow.
The grapevine could see some snow as well as the snow level drops into the afternoon. Watch out for backups and traffic collisions in the area due to the winter weather.
A Winter Storm Warning is in effect in the area mountains from 11 p.m. Monday night until 8 p.m. on Tuesday.
Due to icy winds, with gusts up to 65 mph, and blowing snow, travel to the mountains should be avoided on Tuesday if possible.
The flooding, rain and snow impacted travel all around SoCal on Tuesday morning.
“It’s a very difficult travel day, guys, you’ve got so many elements working against you — the rain, the wind, the snow and the very chilly temperatures,” De Leon said.
That difficulty was evident early in the morning Tuesday, as big rigs and cars slipped and slid all over SoCal freeways, causing multiple accidents ahead of the morning commute.
“It’s a great day to work from home,” NBC4’s Robin Winston said.

As the rain created hazardous conditions, multiple water rescues took place across SoCal.
A vehicle was found in the LA River near East Washington Boulevard, and while the LAFD attempted a water rescue, it was unknown whether the driver was still inside that vehicle.
Another water rescue took place in Sylmar.
A 26-year-old man called 911 from the LA River, where he had fallen into a covered channel near Sylmar High School, according to LA City Fire. He was able to keep ahold of his cell phone and keep it dry, telling firefighters when he could hear their honking as they removed manhole covers from streets above the channel.
He was successfully rescued through a maintenance hole in the street, LA City Fire said. That man is in fair condition and was evaluated by paramedics for minor trauma and mild hypothermia.
Meanwhile, a high wind warning and wind advisory are in effect for the deserts, the coasts and the San Fernando Valley until Tuesday at 1 p.m.
The deserts will see wind between 30 and 40 miles per hour, with gusts up to 70 mph. Areas under advisory will see winds between 20 and 30 mph, with gusts up to 55 mph.
Tie down any loose objects that might become debris, and consider adding extra security to Christmas and holiday decorations.