LOS ANGELES – Forecasters emphasized a rare “high risk” of flash flooding in areas of Southern California, including downtown Los Angeles, on Sunday and Monday. That’s because a powerful atmospheric river is expected to dump several inches of rain across the region.
California Governor Gavin Newsom declared a state of emergency for several Southern California counties to assist with storm response and recovery efforts.
“High risk” is the highest rank on NOAA’s flash flood threat scale and is issued only under the most dire flood forecasts.
The storm has already hit the northern and central parts of the state, with snow already piling up along the Sierra Nevada mountains.
NOAA’s Weather Prediction Center (WPC) said, “In coordination with the (National Weather Service office in Los Angeles), the high-risk area has also been extended south to cover all of Los Angeles County south of the Transverse Mountains. ” he said. “Life-threatening flash flooding and urban flash flooding may occur in high-risk areas.”
The WPC warned that this was a Category 5 atmospheric river, the highest category.
The Golden State has mobilized and pre-positioned a record 8,500 emergency responders for flooding, landslides and travel emergencies. According to the governor’s office.
The state of emergency included Los Angeles, Orange, Riverside, San Bernardino, San Diego, San Luis Obispo and Ventura counties.
The National Weather Service in Los Angeles continues to use strong language in its forecast, indicating a significant threat of widespread and dangerous flash flooding into Monday.
Forecasters warned that flooding problems would not be limited to normally prone areas such as foothills, mountains and burnt areas, and that numerous landslides and debris flows were expected.
In addition, the moist, unstable atmosphere could produce scattered to several severe thunderstorms along and just off the coast of central California.
On Sunday, some storms could produce spray from the Santa Barbara Channel north beyond Santa Cruz to south-central coastal waters.
The NWS said a brief tornado or two could also form as the water spray hits the coast.
The NWS in Los Angeles announced that precipitation could be up to 1.5 inches per hour during thunderstorms. Los Angeles typically receives only 2.89 inches of rain in the entire month of January.
Evacuation orders have been issued in Southern California as heavy rain is predicted to last several days.
‘Extreme’ rainfall totals possible across Southern California
The low-pressure system will send another atmospheric river across the California coast into Monday, bringing large amounts of moisture from the tropics, according to the FOX Prediction Center.
Unlike the last system, this storm is in no hurry to leave. This will send a river of atmospheric moisture toward California for about three days before the rain lingers into Tuesday.
Several television and sporting events scheduled to take place in Southern California on Sunday were postponed due to the extreme threat.
Rain will hit all of California, but the area of greatest concern will be the southern coastal region up to the Los Angeles Basin.
The heaviest rain is expected to fall between Sunday and Monday, with precipitation peaking Sunday night.
On Monday, the Level 4 risk of flooding remained concentrated just above the Los Angeles metropolitan area, while the Level 3 risk extended from just north of Los Angeles south to the San Diego area.
“This is a sign of confidence that we know this is going to be a bigger storm,” Merwin said. “There’s a lot of moisture in there. Southern California has an even bigger flood threat.
More than 5 inches of rain could fall in the Los Angeles metropolitan area by midweek.
Los Angeles averages just over 14 inches of precipitation per year.
As mentioned earlier, 10 to 12 inches of rain was possible in the surrounding mountains and their foothills. 8 to 15 inches of rain is possible in favored mountains and foothills.
Several feet of snow could accumulate in the Sierra Nevada
This plume of moisture could create a significant winter storm in the Sierra Nevada, with 4 to 6 feet of snow possible above elevations of 5,000 to 6,000 feet, according to the FOX Prediction Center.
Disruptions to daily life are expected, including difficult or impossible travel conditions.
In the mountains of Southern California, snow levels are expected to be around 7,000 feet, but above that 2 to 4 feet of snow is possible.
Damaging winds along San Francisco, Central California, and Northern California coasts
In addition to the threat of heavy rain, damaging winds are moving south along the Central California coast toward Santa Barbara. This includes parts of the San Francisco Bay Area.
A high wind warning for winds with gusts up to 110 mph is expected to extend along the coast into the evening and into the evening.
Wind gusts have already been observed at Fant Ranch at 138 mph, Pebble Beach at 105 mph and Oakland at 102 mph.
A driver was injured Sunday morning when a tree fell on top of his car on northbound Interstate 101 in Santa Rosa, about 80 miles north of San Francisco. Sonoma County Fire District.
Elsewhere in Sonoma County, homes were damaged in Bodega Bay after a fallen tree struck a home Sunday morning. officials said. No injuries reported In this case.
Winds will be even stronger in the mountains around Southern California, where gusts could reach 70 to 80 mph.
Early Sunday morning in southern Santa Barbara County, strong winds toppled a 70-foot-tall tree onto an apartment complex in Goleta, authorities said. Scott Safechuck, Public Information Officer, Santa Barbara County Fire Department.
At least four adults and a dog were evacuated from the complex.
On the coast, the winds could whip up the Pacific Ocean with ferocious force, sending waves 10 to 20 feet high onto beaches up and down the state.
Moisture coming in from behind the storm is expected to bring rain for much of this week, but there will be long dry spells between the showers before the rain stops.
First-ever hurricane force wind warning issued off the coast of Central California
The NWS office in the Bay Area issued a first-ever hurricane force wind warning for parts of the Central California coast, warning that mariners could experience wind gusts exceeding hurricane strength (74 miles per hour or more). was issued.
“Very strong winds could create dangerous sea conditions, capsize or damage ships, and significantly reduce visibility,” forecasters wrote in a warning.
