Sierra Snow to Ease West's Drought Next Week

A Much Wetter Pattern is Coming

A much wetter pattern is expected next week, bringing flooding rain and feet of Sierra snow to parts of California. This will also help replenish a western snowpack that has been at record low levels for this time of year, from the Pacific Northwest to the Rockies.

What a strange winter we have seen in the West. Sustained warmth broke records across the region, and there was very little precipitation. However, the warm, dry pattern that dominated much of the winter is finally breaking down. With this change comes cooler temperatures and the chance for rain and mountain snow, which is beneficial for much of the West. But it could become too much of a good thing in California.

It Starts Sunday

Forecast models suggest a much wetter round of precipitation beginning on Sunday and lasting several days next week. With this shift in the weather pattern, there is a chance of days of sustained, locally heavy rainfall across California. This means an increasing flood threat for the state, especially in areas affected by recent fires. The map below shows the highest chance of the heaviest rainfall in the darker green and yellow contours. This includes coastal and Southern California and the Sierra foothills at elevations low enough for rain to fall.

California's snowpack will also see a major boost. Specifically, feet of Sierra snowfall and some heavy snowfall in the Southern California mountains are likely next week. Travel in this higher terrain will become increasingly challenging, if not impossible, at times.

Despite the travel challenges, this boost in Sierra snowpack is needed, as it's currently running only about 50% of average for this time of the year, according to the California Department of Water Resources.

Why The Shift?

Most of the winter has seen the jet stream riding well north into western Canada, then plunging southward into the East. This pattern leads to less rainfall and warmer temperatures out West. The graphic below shows what will happen next week. The jet stream will instead take its sharp southward plunge into the West, leading to cooler temperatures and an influx of much-needed rain and snow.

Why Snowpack Matters

The snowpack across the West isn't just for skiers and snowboarders. It also helps provide a freshwater source to the West during the drier months. This is why the lack of snowfall has been so concerning. The West is dependent on snow, which they haven't been seeing.

According to the National Resources Conservation Service, dozens of locations from Colorado and Utah to the Pacific Northwest have snowpack that is lowest at this time of year in at least a decade or more.

First Round Recap

The first round of rain and snow arrived in California on Tuesday and wrapped up by the end of the day on Wednesday. Parts of central and Southern California picked up 1 to 2 inches of rain. There were about two dozen reports of mainly minor flash flooding.

Winds gusted from 60 to 70 mph in a few areas, a few trees or tree limbs were downed in parts of Southern California, and just under 8,000 customers lost power in the state. All in all, this was mainly an appetizer round for the Golden State.

There was also some snowfall across the Sierra. Mammoth Mountain Ski Base saw 17 inches, the highest snow total in the Sierra.

About the Author

Rob Shackelford is a meteorologist and climate scientist at weather.com. He received his undergraduate and master’s degrees from the University of Georgia studying meteorology and experimenting with alternative hurricane forecasting tools.