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Atmospheric river bringing large amounts of rain & snow to California

Atmospheric River
Posted at 6:31 PM, Jan 04, 2023
and last updated 2023-01-04 21:59:43-05

It's been a wet winter across the West Coast, and new tonight, a high-powered storm is making headlines as it bears down on the Golden State.

The state is expected to be ground zero for the worst of the weather through the end of the week.

A large, hurricane force-like low pressure system will combine with plenty of moisture to bring flooding rains, heavy mountain snow, powerful swells of more than 20 feet to the coast, and wind gusts up to 70 mph.

It's all part of an atmospheric river event that's going to bring several rounds of heavy rain and snow to the state over the next week as several more storms are lined up behind this one.

Atmospheric rivers, which are sometimes referred to as the *Pineapple Express*, contain narrow bands of super concentrated amounts of water vapor, or moisture.

These originate in the sub-tropics and when they encounter land, can bring intense bursts of precipitation that can last for days.

The extreme weather could bring as much as 3-6" of rain to the Golden State through midday Saturday.

The potential for this much water to fall in a short amount of time could trigger mud and debris flows in the state, as well significant urban flooding.

California rainfall potential through midday Saturday, January 7, 2023

With the source of the moisture more tropical in nature, snow levels will be high at the onset of the storm, starting out around 6,500-7,500 feet in the Sierra. By Thursday afternoon, snow levels may drop to as low as 4,000-5,000 feet.

In the Sierra Nevada Mountains, snow will once again be measured in feet, with as much as 2-4 of snow in some areas.

Snow accumulation potential for California through midday Saturday, January 7, 2023

By the time that the storm reaches Utah, the storm will have much less moisture to work with. Snow is likely here from Thursday afternoon through Friday afternoon, with some areas picking up an additional 6-12" of fresh powder.

Snow accumulation potential for Utah through midday Saturday, January 7, 2023

Finally here in Colorado, our best chances for snow in the mountains will come from late Thursday night into Friday evening.

Compared to what we'll see this week in California and Utah, snow totals will be relatively light, somewhere between 2-5".

Snow accumulation potential for Colorado through midday Saturday, January 7, 2023

This particular atmospheric river event will largely miss Colorado, other than some light mountain snow showers Thursday night and Friday.

As for the Plains and I-25 corridor...don't count on much of anything!

So why not us?

We can look at two main reasons to explain why we'll miss out on the action in Colorado.

The first has to do with the storm's more northerly track.

The second has to do with topography, i.e., the mountains.

The high mountain peaks of the Sierra Nevada will squeeze out the majority of the rain and snow from this storm system before it even has the chance to reach us here in Southern Colorado.