Soaking storm setting sights on Southern California
By
Alex Sosnowski, AccuWeather senior meteorologist
Published Dec 13, 2021 1:37 PM EST
|
Updated Dec 14, 2021 5:10 PM EST
A storm already responsible for travel-snarling snow in the mountains and drenching rain in the lower elevations much of the Pacific Coast states this past weekend will focus its onslaught on the Southwest and Southern California, in particular, into Tuesday night.
The storm currently bringing rain and snow to the West Coast, and perhaps another that follows next week, will likely be the most disruptive in terms of creating travel concerns and producing the greatest risk of mudslides. But the overall pattern is good news for drought concerns as storms line up like a parade over the northern Pacific Ocean, AccuWeather meteorologists say.
Through Monday morning, local time, the storm had already dropped 1-2 inches of rain on the San Francisco Bay Area and about an inch or so of rain on the Sacramento Valley. Snow was piling up at the rate of a few inches per hour over the high country of the Sierra Nevada.
Storms continued to line up over the Pacific basin with one storm rolling into Southern California (lower right), another over the Gulf of Alaska (top center) and a third over the Bering Sea (upper left) on Tuesday, Dec. 14, 2021. (CIRA at Colorado State/GOES-West)
When this particular storm is all said and done, about 4 inches of rain will have fallen on the San Francisco area with 3 to perhaps 4 inches in parts of the Sacramento Valley. In the central Sierra Nevada, a whopping 2-4 feet of snow will pile up with local amounts to 6-8 feet over the highest elevations by Tuesday night. The rate of snow may vary significantly and could range from light and intermittent one hour to as much as several inches per hour the next.
Crews may struggle to keep roads open with the heavy rate of snow and vehicles that become stuck may impede snow removal operations. Snow and snowfall rates of this magnitude can strand motorists and result in a life-threatening situation. Meteorologists say travel over Donner Pass, California, along Interstate 80 and other roads over the high country should be avoided until the storm concludes by midweek.
This image shows storm total rainfall through midday Tuesday.
The heavy amount of snow on the steep slopes of the Sierra Nevada and Cascades will substantially increase the risk of avalanches into midweek. So, even as the snow moves away and roadways are cleared, there will continue to be some ongoing dangers.
"The storm and its heavy precipitation will pivot through Southern California through Tuesday evening," AccuWeather Senior Meteorologist Dan Pydynowski said. He noted that the region would experience the worst impacts from the storm on Tuesday with flash flooding and the risk of mudslides possible.
The Los Angeles area had already received 1-2 inches of rain as of the midday hours on Tuesday from the storm and another inch or two may pour down into Tuesday night. "This is definitely one of the biggest and most impactful single storms of 2021 for this part of Southern California," Pydynowski said.
From 1-2 inches of rain is forecast to fall on the San Diego area into Tuesday night.
In terms of rainfall for Northern California, perhaps only the storm from Oct. 20-25 may have been heavier. That storm deposited between 5 and 7 inches of rain on San Francisco and Sacramento. The same storm only brought 0.50 of an inch to 1 inch of rain on much of coastal Southern California.
Too much rainfall won't be the only concern. As cold air pivots in on the backside of the storm, the air is likely to cool enough for freezing levels to dip down to the pass levels of Southern California along the Grapevine and I-5 as well as I-15.
"It probably will not snow long enough for a big accumulation of snow on the roads over Cajon and Tejon passes, but there can be enough to make for slippery and slushy conditions for the evening commute Tuesday," Pydynowski said.
Winter storm warnings have been issued for mountainous areas in parts of Ventura and Los Angeles counties, according to the National Weather Service. High wind warnings have also been issued for a broad portion of Southern California.
Over 50 inches of snow was measured at some of the higher elevations of the Sierra, including a whopping 6.3 feet at Mount Rose.
The same storm will bring snow to the interior higher elevations of the Southwest. The city of Flagstaff, Arizona, is expected to pick up a few inches of snow Tuesday night. Since the storm is predicted to pick up forward speed while pivoting through the interior West, the various mountain ranges from Arizona to Colorado are likely to be spared several feet of snow, but a fresh 1-2 feet of powder seems likely for the high country.
The storm will pack enough moisture for a thorough soaking around Las Vegas, while a couple of showers are likely to dampen the roads around Phoenix. The same storm is predicted to produce a swath of strong winds from the deserts to the central and southern Plains at midweek. Not only will winds be strong enough to kick up dust and raise the risk of wildfire ignition and rapid spread, but also the potential for localized to regional power outages.
A substantial break in the stormy pattern is not anticipated as more storms are expected to churn through the Pacific and reach the West Coast early next week.
"The overall pattern remains right for additional storms to drop southward from just off the British Columbia coast and across much of the West Coast of the U.S. this week and into next week," AccuWeather Senior Meteorologist Brett Anderson said, adding that while most of these additional storms do not appear to be as strong as the system at the start of this week, they will bring more rounds of rain and mountain snow from Washington to California.
The next storm in the series will begin to produce rain and mountain snow in western Washington as early as Tuesday night. Even though this storm is projected to weaken upon moving southeastward along the Pacific coast from Wednesday to Thursday, several hours of soaking rain seem likely for the San Francisco and Sacramento areas Wednesday night. Enough moisture may survive the trip to bring spotty showers to Los Angeles, San Diego and Las Vegas on Thursday.
Several more inches of snow may seem like icing on the cake in the Cascades and Sierra Nevada from the storm, but it will continue to add to the snowpack for future melting and replenishment of stream and reservoir levels in the spring.
A third storm is projected to roll ashore in the Northwest this weekend and could bring some low-elevation rain showers and mountain snow to Northern California. Even if that storm is unsuccessful at bringing rain and mountain snow to Southern California, another large storm will arrive next week to bring more opportunities for rain and mountain snow as December continues.
The stormy pattern will continue to chip away at the long-term drought in the region, while each round of moisture adds another delay to the potential for renewed wildfires. Prior to the storm that began this past weekend in Northern California, 80% of the Golden State and about 50% of the Western states, in general, were experiencing severe to exceptional drought. Only in western Washington and a few counties in northwestern Oregon has drought been erased by storms this autumn.
For the latest weather news check back on AccuWeather.com. Watch the AccuWeather Network on DIRECTV, Frontier, Spectrum, fuboTV, Philo and Verizon Fios. AccuWeather Now is now available on your preferred streaming platform.
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News / Weather Forecasts
Soaking storm setting sights on Southern California
By Alex Sosnowski, AccuWeather senior meteorologist
Published Dec 13, 2021 1:37 PM EST | Updated Dec 14, 2021 5:10 PM EST
A storm already responsible for travel-snarling snow in the mountains and drenching rain in the lower elevations much of the Pacific Coast states this past weekend will focus its onslaught on the Southwest and Southern California, in particular, into Tuesday night.
The storm currently bringing rain and snow to the West Coast, and perhaps another that follows next week, will likely be the most disruptive in terms of creating travel concerns and producing the greatest risk of mudslides. But the overall pattern is good news for drought concerns as storms line up like a parade over the northern Pacific Ocean, AccuWeather meteorologists say.
Through Monday morning, local time, the storm had already dropped 1-2 inches of rain on the San Francisco Bay Area and about an inch or so of rain on the Sacramento Valley. Snow was piling up at the rate of a few inches per hour over the high country of the Sierra Nevada.
Storms continued to line up over the Pacific basin with one storm rolling into Southern California (lower right), another over the Gulf of Alaska (top center) and a third over the Bering Sea (upper left) on Tuesday, Dec. 14, 2021. (CIRA at Colorado State/GOES-West)
When this particular storm is all said and done, about 4 inches of rain will have fallen on the San Francisco area with 3 to perhaps 4 inches in parts of the Sacramento Valley. In the central Sierra Nevada, a whopping 2-4 feet of snow will pile up with local amounts to 6-8 feet over the highest elevations by Tuesday night. The rate of snow may vary significantly and could range from light and intermittent one hour to as much as several inches per hour the next.
Crews may struggle to keep roads open with the heavy rate of snow and vehicles that become stuck may impede snow removal operations. Snow and snowfall rates of this magnitude can strand motorists and result in a life-threatening situation. Meteorologists say travel over Donner Pass, California, along Interstate 80 and other roads over the high country should be avoided until the storm concludes by midweek.
This image shows storm total rainfall through midday Tuesday.
The heavy amount of snow on the steep slopes of the Sierra Nevada and Cascades will substantially increase the risk of avalanches into midweek. So, even as the snow moves away and roadways are cleared, there will continue to be some ongoing dangers.
"The storm and its heavy precipitation will pivot through Southern California through Tuesday evening," AccuWeather Senior Meteorologist Dan Pydynowski said. He noted that the region would experience the worst impacts from the storm on Tuesday with flash flooding and the risk of mudslides possible.
The Los Angeles area had already received 1-2 inches of rain as of the midday hours on Tuesday from the storm and another inch or two may pour down into Tuesday night. "This is definitely one of the biggest and most impactful single storms of 2021 for this part of Southern California," Pydynowski said.
From 1-2 inches of rain is forecast to fall on the San Diego area into Tuesday night.
In terms of rainfall for Northern California, perhaps only the storm from Oct. 20-25 may have been heavier. That storm deposited between 5 and 7 inches of rain on San Francisco and Sacramento. The same storm only brought 0.50 of an inch to 1 inch of rain on much of coastal Southern California.
Too much rainfall won't be the only concern. As cold air pivots in on the backside of the storm, the air is likely to cool enough for freezing levels to dip down to the pass levels of Southern California along the Grapevine and I-5 as well as I-15.
"It probably will not snow long enough for a big accumulation of snow on the roads over Cajon and Tejon passes, but there can be enough to make for slippery and slushy conditions for the evening commute Tuesday," Pydynowski said.
Winter storm warnings have been issued for mountainous areas in parts of Ventura and Los Angeles counties, according to the National Weather Service. High wind warnings have also been issued for a broad portion of Southern California.
Over 50 inches of snow was measured at some of the higher elevations of the Sierra, including a whopping 6.3 feet at Mount Rose.
The same storm will bring snow to the interior higher elevations of the Southwest. The city of Flagstaff, Arizona, is expected to pick up a few inches of snow Tuesday night. Since the storm is predicted to pick up forward speed while pivoting through the interior West, the various mountain ranges from Arizona to Colorado are likely to be spared several feet of snow, but a fresh 1-2 feet of powder seems likely for the high country.
The storm will pack enough moisture for a thorough soaking around Las Vegas, while a couple of showers are likely to dampen the roads around Phoenix. The same storm is predicted to produce a swath of strong winds from the deserts to the central and southern Plains at midweek. Not only will winds be strong enough to kick up dust and raise the risk of wildfire ignition and rapid spread, but also the potential for localized to regional power outages.
A substantial break in the stormy pattern is not anticipated as more storms are expected to churn through the Pacific and reach the West Coast early next week.
"The overall pattern remains right for additional storms to drop southward from just off the British Columbia coast and across much of the West Coast of the U.S. this week and into next week," AccuWeather Senior Meteorologist Brett Anderson said, adding that while most of these additional storms do not appear to be as strong as the system at the start of this week, they will bring more rounds of rain and mountain snow from Washington to California.
The next storm in the series will begin to produce rain and mountain snow in western Washington as early as Tuesday night. Even though this storm is projected to weaken upon moving southeastward along the Pacific coast from Wednesday to Thursday, several hours of soaking rain seem likely for the San Francisco and Sacramento areas Wednesday night. Enough moisture may survive the trip to bring spotty showers to Los Angeles, San Diego and Las Vegas on Thursday.
Several more inches of snow may seem like icing on the cake in the Cascades and Sierra Nevada from the storm, but it will continue to add to the snowpack for future melting and replenishment of stream and reservoir levels in the spring.
A third storm is projected to roll ashore in the Northwest this weekend and could bring some low-elevation rain showers and mountain snow to Northern California. Even if that storm is unsuccessful at bringing rain and mountain snow to Southern California, another large storm will arrive next week to bring more opportunities for rain and mountain snow as December continues.
The stormy pattern will continue to chip away at the long-term drought in the region, while each round of moisture adds another delay to the potential for renewed wildfires. Prior to the storm that began this past weekend in Northern California, 80% of the Golden State and about 50% of the Western states, in general, were experiencing severe to exceptional drought. Only in western Washington and a few counties in northwestern Oregon has drought been erased by storms this autumn.
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