Atmospheric River Targets California with Heavy Rain, Flood Risk, and Potential end to Fire season
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California is bracing for a significant weather event this week as a fast-moving atmospheric river is forecast to bring periods of heavy rain, potential flooding, and debris flows, especially in areas recently impacted by wildfires.The storm is expected to arrive in Northern California on Wednesday before impacting Southern California on thursday and possibly lingering through Saturday.
The National Weather Service (NWS) has warned that this system could deliver the most rainfall to downtown los Angeles in at least a month, and possibly since February.”There is a chance for burn area flash flooding and debris flow issues. A flood watch will be possible for burn scars,” stated a meteorologist with the NWS office in Oxnard on Tuesday afternoon.
While the storm presents clear hazards, officials also suggest it could mark a turning point in california’s prolonged autumn fire season. Recent rainfall in Northern California has already reduced fire danger in that region,and similar conditions are anticipated in southern California. The NWS office in Oxnard characterized the approaching storm as “potentially significant,” forecasting flooded roadways, possible rockslides on canyon roads, and the threat of mudflows.
Commute and Coastal Impacts Expected
The storm is likely to disrupt travel in Los Angeles and Ventura counties during the Thursday afternoon and Friday commutes, with ponding water on roadways anticipated. Forecasters warn that the Los Angeles metropolitan area could be particularly vulnerable to localized freeway flooding in low-lying areas. Rainfall totals are expected to range from 1 to 2 inches along the coast and in the valleys, increasing to 2 to 4 inches in the mountains and foothills.
“We’re looking at moderate to locally heavy rain rates with this system,” the NWS meteorologist explained. Specific rainfall predictions include 1.08 inches for Long Beach, approximately 1.3 inches for downtown Los Angeles, Redondo Beach, Pomona, and Pasadena, 1.51 inches for Oxnard, 1.75 inches for Santa Clarita, 1.98 inches for Westlake Village,2.22 inches for Santa Barbara, and 2.88 inches for Ojai.
Wind and Debris Flow Concerns
In addition to rainfall, strong winds are expected. Peak gusts could reach 50 mph along the Grapevine section of the 5 Freeway and in the Antelope Valley, while downtown Los Angeles could experience winds of 21 mph, increasing to 24 mph in Long Beach, 26 mph in santa Clarita, 32 mph in Redondo Beach, and 39 mph in Lancaster.
Rainfall rates of 0.25 to 0.5 inches per hour are possible, increasing the risk of debris flows in recent burn scars. The NWS is closely monitoring the situation and will issue further warnings as needed. This “cutoff low pattern” – a notoriously difficult weather phenomenon to predict, often referred to as “weatherman’s woe.” This pattern could lead to thunderstorms across California,bringing the possibility of small hail,gusty winds,heavy downpours,and lightning strikes.
Impacts Beyond Southern California
The San Francisco Bay Area is expected to experience the most intense rain late Wednesday and Thursday, with most areas receiving between half an inch and an inch of rain, and higher amounts in the mountains. Wind gusts could reach 60 mph, potentially causing downed trees and power outages. Sacramento could receive up to 2 inches of rain.
The Sierra Nevada is also bracing for heavy snow. A winter storm warning has been issued from 1 a.m. Thursday until 4 p.m. Friday for elevations above 7,500 feet in Mono County.Travel is strongly discouraged between Thursday morning and friday morning, with Donner Peak potentially receiving 12 to 18 inches of snow. The California Highway Patrol is expected to require chains for motorists crossing the Sierra Nevada. Snow accumulation could reach 1 to 2 feet on the sierra Crest and 4 to 12 inches along Highway 395.Wind gusts in the Sierra could exceed 100 mph along the ridgetops.
Despite the hazardous conditions, Mammoth Mountain is celebrating the early start to the ski and snowboarding season, moving its opening day to Saturday. “Winter’s loading,” the resort announced on its website. “Get ready for a stronger start to the season!” Northstar and heavenly near Lake Tahoe are scheduled to open on November 21st, followed by Palisades Tahoe on November 26th.
