UPDATED with latest: A strong storm system is expected to “blast through” Los Angeles and Orange County tonight, bringing a heavy dose of rain over a short period of time and prompting evacuation orders, flood warnings and road closures.
“A fast moving cold front will blast through the area overnight with most of the steady rain finished by 8 a.m. Thursday, if not sooner,” the National Weather Service said. “Despite the relatively fast speed, the system will pack quite a punch with a 60-80% chance of hourly and/or sub-hourly rates to exceed debris flow thresholds somewhere in the foothills and mountains and possibly in other areas as well.”
Per the NWS, “The necessary ingredients will be in place to generate a 3 to 6 hour period of very heavy rain tonight, especially near and on the south facing mountain slopes from Santa Barbara to L.A. County. Hi-res ensembles have been consistent showing a 60-80% chance of rain rates reaching a half inch per hour somewhere in those upslope areas and a 10-20% chance of hourly rates close to an inch per hour.”
“Thursday will be a mixed bag of weather conditions with rapidly lowering snow levels, increasing air mass instability with isolated thunderstorms, as well as periods of no rain and some sunshine,” according to the NWS. “Rain could be very heavy at times with small hail and snow as low as 2500-3000 feet. Travel over some of the mountain passes may not be possible at times and travel delays and closures should be expected.”
Additionally, “small hail, gusty winds, and possibly even a waterspout or small tornado are all possible through the day so the threat of flooding and debris flows will continue through at least Thursday afternoon.” Those winds could reach 45-65 mph in some areas, according to the forecast.
On Friday, “another area of showers is expected to move through Friday into early Saturday. Additional amounts are expected to from around a half inch north of Pt Conception to around a quarter inch or less south.”
The weekend should be clear.
With Los Angeles County facing nearly an inch of rain per hour during the storm’s peak, officials issued evacuation warnings and “address specific” evacuation orders in places vulnerable to mudslides, including recent burn areas, the Los Angeles Fire Department announced Tuesday.
The city of Sierra Madre also issued evacuation orders and warnings Wednesday for several areas in the foothills of the San Gabriel Mountains. A Nixle Alert said there would be no street parking allowed in the affected areas. They can be found at sierramadreca.gov/.
All evacuation orders and warnings were in effect from 7 a.m. Wednesday to 6 p.m. Thursday.
Officials said the following burn areas were “especially susceptible to heavy rain”:
— Palisades Fire: Getty Villa area, Highlands near the burn areas, Bienveneda area near Temescal Canyon Park, Rivas Canyon/Will Rogers State Park area, Mandeville Canyon above Tanners Road, Old Ranch Road and Rustic Creek;
— Sunset Fire: East and south of Runyon Canyon;
— Hurst Fire: Olive Lane in the Oakridge Mobile Home Park;
Houses in the warning area with high risk were being visited by the Los Angeles Police Department on Tuesday to receive specific evacuation orders. If residents are not home, the department was leaving a flyer with relevant information.
PREVIOUSLY on Tuesday: With an atmospheric river funneling a series of late-winter storms that are expected to bring heavy rainfall to Los Angeles, local officials were issuing evacuation warnings and “address specific” evacuation orders in places vulnerable to mudslides, including recent burn areas, the Los Angeles Fire
Department announced Tuesday.
Los Angeles County faces substantial rain for the next two days — nearly an inch per hour during the storm’s peak — with the possibility of lingering showers on Friday.
Houses in the warning area with high risk are being visited by the Los Angeles Police Department on Tuesday to receive specific evacuation orders. If residents are not home, the department is leaving a flyer with relevant information. The evacuation orders will be in effect from 7 a.m. Wednesday to 6 p.m. Thursday.
Fire officials said the following burn areas were “especially susceptible to heavy rain”:
— Palisades Fire: Getty Villa area, Highlands near the burn areas, Bienveneda area near Temescal Canyon Park, Rivas Canyon/Will Rogers State Park area, Mandeville Canyon above Tanners Road, Old Ranch Road and Rustic Creek;
— Sunset Fire: East and south of Runyon Canyon;
— Hurst Fire: Olive Lane in the Oakridge Mobile Home Park
Some residents also received cell phone alerts with the relevant information.
A flood watch was also expected from Wednesday at 6 p.m. to Thursday 6 p.m.
Additionally, Caltrans will close a segment of Pacific Coast Highway to residents and businesses in burn scar areas at noon Wednesday due to safety concerns from the incoming storm. Only emergency vehicles and U.S. Army Corps of Engineers debris-hauling contractors will be allowed through the closure.
Caltrans and other officials will reassess the situation Thursday to determine if the highway can reopen to residents and businesses with passes by Friday for the morning commute, if not earlier. That decision is dependent on the extent of the storm and resulting impacts of any debris flows.
L.A. County Public Works crews have prepared debris basins, stabilized slopes, and reinforced drainage systems to reduce flood risk, particularly in recent burn areas including Eaton, Palisades, Bridge, Hurst, Kenneth, Hughes, Sunset, Lidia and Franklin, officials said.
“While these efforts reduce flood risk, the storm could still bring moderate debris and mudflows to burn areas, potentially blocking streets and threatening structures depending on their location and the local terrain,” the department said in a statement.
“To mitigate potential impacts, LA County Public Works has activated 24/7 storm patrols and remains fully mobilized,” officials added.
Through Tuesday night, rainfall was expected to range from one-third to two-thirds of an inch from the coast to the mountains with local amount exceeding one inch in the mountains, per the National Weather Service.
A cold front will move over the area overnight Wednesday into early Thursday, bringing a storm with potential flooding.
“Lighter precipitation will develop on Wednesday with the with the most likely time for more widespread and heavier precipitation with the cold front for late Wednesday night into Thursday morning,” the NWS said.
Rainfall is expected to range from 1 to 2 inches along the coast and in valley areas and 2 to 4 inches in the foothills and mountains. Rainfall rates could reach up to .75 inches per hour.
This system will also likely be the biggest snow maker of the season, with 1 to 2 feet of snow forecast for higher elevations.
“Steady rain will turn to showers Thursday. The snow levels will drop to around 3,000 ft and a few inches of snow is possible over the Grapevine and other lower elevations passes,” the NWS predicted.
Stronger, gusty southwest to west winds will develop Wednesday night and continue through Thursday night, per the NWS.
A weaker storm system moving inland to the north on Friday could keep some showers going into Friday night, according to forecasters. However, things dry out and warm up for the weekend.
City News Service contributed to this report.
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