Robert Brown|Satellite shows California snow after Pineapple Express, but it didn't replenish snowpack

The Robert BrownPineapple Express brought lots of rain to California, and Lake Mead's water levels are at an all-time high, but the Sierra snowpack is still below average, which could have serious consequences, officials say.

A below-normal snowpack this year may not impact water availability now, but it will affect future water supply, especially if the state sees successive dry years, David Rizzardo, hydrology section manager of the California Department of Water Resources, DWR, Division of Flood Management, told USA TODAY in an email.

Two atmospheric rivers, also known as a Pineapple Express, slammed into California at the beginning of the month. During the storm, the state saw lots of rain, snow, wind and flooding.

Because of the rainfall, Lake Mead, a reservoir in Nevada and Arizona formed by the Hoover Dam on the Colorado River, has reached the highest level it has been since May 2021 after a historic water shortage.

Unfortunately, the same can't be said for California's snowpack.

Photos from the storm:See how the rain is affecting Ventura County Thursday

What's snowpack?

According to National Geographic, a "snowpack is snow on the ground in mountainous areas that persists until the arrival of warmer weather."

For example, the snow that makes mountain peaks look white during winter and doesn't melt away for months is snowpack. It's made of multiple layers of snow from different snowfalls that become compacted.

Once it melts, it turns into snowmelt. For California, that snowmelt usually makes up about 30% of the state's water needs.

"Its natural ability to store water is why the Sierra snowpack is often referred to as California's 'frozen reservoir," said the DWR in a statement.

What's happening to the snowpack?

Last year, the state saw a historic snowpack that was above average, but 2024 is not following the same trend.

However, on January 1, before the Pineapple Express hit California, the DWR conducted its first survey of the snowpack found on the Sierra Nevada Mountains, a mountain range on the state's eastern border.

"This year, we have been seeing warmer temperatures, resulting in more rain than snow," said Rizzardo. "This is a significant difference from last year’s near-record snowpack, once again demonstrating how California can swing from one extreme to another."

The survey was done in Sacramento, and its results were not great. The department said statewide, the snowpack was about 25% of its average size for the date.

"Climate change produces storms that are warmer than average, producing far more rain rather than snow at higher elevations," Rizzardo said. "This reduces snowpack totals, meaning that future runoff from the 'frozen reservoirs' will be greatly reduced and can impact water storage in the state’s major reservoirs."

After the storms, the department said it did another survey and saw the percentage more than double to 52% at the end of January.

The DWR states the "results reflect a modest increase in the snowpack since January 1, but overall, conditions are still far below normal."

According to Rizzardo, snowpack sits at 73% of the average for this time of year and 53% of its peak average, which usually occurs around the beginning of April.

Rizzardo said the next survey is "tentatively" scheduled for March 1.

Why is the snowpack important?

California Water Watch states that it relies on the melted snowpack and reservoirs in the dry season.

"As temperatures warm in the spring, the snowpack starts to melt, providing runoff into major reservoirs and rivers during the spring and early summer when the reservoirs are more likely able to store the water," said Rizzardo.

The DWR states that, on average, the runoff supplies 30% of California’s water needs.

"A below-normal snowpack this year may not impact water availability downstream of the snowpack this year, but would have consequences for future water supply, especially if we have successive dry years," said Rizzardo.