California and the West Braces for Multiple Rounds of Moisture

Posted: February 3, 2023 4:31 pm

It has been a relatively calm several days across the West Coast, allowing the region to catch its breath after it was hammered with rain and snow to end 2022 and start 2023. However, that is all about to change as a new parade of storms moves in from the Pacific Ocean starting late Friday. Here is what you can expect with this latest round of storms in terms of precipitation amounts, intensity, and timing.

Pacific Storm Track Fires Up Along West Coast Again

The change in the weather will come at the hands of a west-to-east flow across the jet stream, setting the stage for a series of swiftly moving storms to move in from the Pacific. While the storms will not rival what the region saw last month, they will still be packed with a good amount of moisture.

Another difference between last month’s weather maker and this round of storms is that the track will take the moisture slightly farther to the north, putting Northern California and the Pacific Northwest in the crosshairs. The primary impacts of these storms will be isolated flash flooding, travel delays across the Sierra Nevada and the Cascade Mountains because of snow, and debris flows.

Timing of Storms

The first storm is forecast to arrive on Friday. This initial event will be weaker in nature, bringing rain showers to an area expanding from Central California into western Washington. The west-facing Coast Ranges north of the San Francisco Bay Area can expect to see 0.50 of an inch to 1 inch of rain throughout the day Friday and into the overnight hours.

The valleys of California will likely be spared the bulk of the moisture because the storm track will take it to the north at a fast clip. The Sierra Nevada will also dodge a significant amount of snow accumulation from the first system, however, the system will produce several inches of new snow for interior mountains of Northern California and Oregon.

The next storm will pack more of a punch as it moves farther to the south and inland than its predecessor. This storm will impact the region on Saturday and Sunday. The Coastal Ranges near San Francisco and the Sierra Nevada foothills can expect to see 1 – 2 inches of rain.

Like the first storm, Southern California will not likely be impacted with substantial rain. This part of the Golden State may see a few isolated showers but no meaningful rainfall.

The Sierra Nevada will pick up a general 1 – 2 feet of snow with levels dropping as low as 4,00 feet. Localized areas may see up to 3 feet of new accumulation out of this weekend storm.

Rain and Snow Provided Significant Drought Relief in Recent Weeks

Looking ahead, forecasters are calling for an active storm track to set up across the Pacific Coast into February. The long-range forecast is indicating a storm to move into Southern California during the weekend of February 11 – 12. Be sure to stay tuned to your local forecast in the coming days if you live in this area.

While this rain may be a nuisance for those hoping to escape to California for some sun and warmth, it is good news for the state’s ongoing drought. The problem with last year’s weather pattern is that the moisture valve shut off completely during the months of February and March. A more average rainfall season this year would bring significant relief to the drought situation.

According to the latest data out of the U.S. Drought Monitor, the storms from December and January have provided substantial relief to California. There are no parts of the state under the designation of an extreme or exceptional drought. Additionally, many of the state’s most important reservoirs have reached average levels once again.

Snowpack is also looking good heading into the dry season. For instance, the southern slopes of the Sierra Nevada are hovering around 170% of normal with the northern slopes coming in at a whopping 250% of normal.

This snowpack will yield great dividends in the coming months as it melts and flows down into the streams below. These streams then flow into the state’s lakes and reservoirs, boosting water levels in time for the dry summer season.

Impacts of a Weakening La Niña System

After holding in place for the last few years, the current La Niña pattern is beginning to weaken. This gradual weakening is forecast to continue for the next several months, bringing more moisture to the West Coast. The onset of an El Niño climate pattern would direct more storms into California next winter. However, it is still too early to determine when this transition from La Niña to El Niño would occur. How this unfolds will greatly influence what California and the rest of the West Coast can expect for precipitation in the fall and winter of 2023.

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