What you should know
- Possibly the biggest storm of the season will hit SoCal on Monday around midnight, with the heaviest rainfall expected on Tuesday morning.
- The region could see 1 to 3 inches of rain, and the mountains of the region could see 1 to 2 feet of snow over 7,000 feet.
- Be on the lookout for gusts of wind, road flooding, high surf, fallen trees, and possible flash floods.
Pull out your umbrellas, rain boots, and coats – Southern California will see a major winter storm, with rain starting Monday night and soaking the area all Tuesday.
It could be the biggest storm of the season for our region, and it is expected to drop between 1 inch and 3 inches of rain over SoCal when the brunt of the storm hits the region.
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Here’s what to expect for Tuesday’s storm, possibly the biggest of the season for SoCal.
Timed coordination
This storm occurred in the northwestern United States over the weekend, with it raining in northern California on Sunday morning.
By Monday morning, the Bay Area was already soaked when an already powerful storm system joined forces with an atmospheric river.
The weather system will reach Southern California on Monday night. There can be light showers throughout the day as the clouds increase, but things stay dry mostly until later.
It is expected to rain overnight and likely to start in earnest around midnight, with the heaviest rainfall falling on Ventura County.
The heaviest rain is expected to hit Los Angeles County around 7 a.m. on Tuesday. Road flooding and slippery road conditions may occur during the Tuesday morning commute.
The storm system on its own is cold and strong, but becomes more intense after joining an atmospheric flow. The clouds will increase as the day progresses, with it starting to rain on Monday night and getting heavier on Tuesday morning. Belen De Leon has the forecast for December 13, 2021.
Rainfall will be moderate to heavy over Orange County and the Inland Empire at around 9 a.m. on Tuesday, and the showers will continue through the afternoon and taper into the evening.
During the afternoon, waves of moisture will move inland as snow depth in the mountains drops from 2,000 feet at the start of the storm to 4,000 feet in the evening.
The rain will stop around Tuesday night with persistent snow showers in the mountains.
Expected rain and snowfall
The combination of the pre-existing storm with the atmospheric flow is why SoCal will see so much moisture and why the rains will be so intense, according to NBC4 meteorologist Belen De Leon.
“Well, this system is cold, it’s a powerful one in itself,” she said. “But it combines with some tropical moisture, an atmospheric flow.”
That means our region could get between one and three inches of moisture in urban areas and between three and six inches of moisture in the foothills and mountains.
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A major storm in December will inundate SoCal, which starts overnight on Monday and comes down hard on Tuesday morning.
With all of the snow falling in the mountains and the level of snow decreasing over the course of Tuesday, we could see accumulations of snow between one and one meter over 2,000 feet in elevation.
About 4,000 feet await between one and three inches of snow. It is also possible for the grapevine to see up to two inches of snow, although it is not yet clear whether this snow is sticking.
Impact & Warnings
From Monday the wind increases in the deserts and reaches its peak in the afternoon. For the deserts, the coasts and the San Fernando Valley, a strong wind warning and wind warning apply until Tuesday at 1 p.m.
Tuesday’s storm could be the strongest storm we see in our area this season and the water will arrive on Monday evening. Until then we have dry weather. Shanna Mendiola has the forecast for December 12, 2021
In the deserts, winds will be seen between 30 and 40 miles per hour with gusts of up to 70 miles per hour. In the advisory areas, winds between 20 and 48 km / h with gusts of up to 55 km / h are observed.
The wind can knock over some trees in the area, and high profile vehicles should be careful when driving on highways as the wind makes driving more difficult.
Tie up any loose items that could become rubble and consider adding extra security to Christmas and holiday decorations.
In the mountains region, a winter storm warning applies from Monday evening 11 p.m. to Tuesday 8 p.m.
Due to icy winds with gusts of up to 100 km / h and blowing snow, you should avoid traveling to the mountains on Tuesday if possible.
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Much of SoCal was under flood surveillance during a storm in December 2021.
Much of the region has been under flood protection since Monday afternoon, with debris flows near the scars of the recent forest fires.
In urban areas and on roads, it is likely that it will rain hard enough and fast enough to cause flooding, especially after the heaviest rainfall has fallen and lighter showers become possible on Tuesday afternoons.
A flash flood warning has been issued for the Alisal burn scar region in the Santa Barbara district, where the heaviest rain will fall on Tuesday before sunrise.
High winds create dangerous boating conditions, with waves ranging from two to nine feet in the LA and Ventura County waters. Rip currents are also expected on west-facing beaches, with gusts of wind on the coast reaching up to 45 miles per hour.
The waves will be steep and choppy from Monday and last until Wednesday.
Parts of San Bernardino County were placed under evacuation warning on Sunday afternoon before Tuesday’s storm.
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