How Snowfall Will Change Lake Mead's Water Levels

An El Niño winter snowfall map from the National Oceanic and Atmospheric Administration (NOAA) predicted more good news for Lake Mead.

After years of drought the lake, located in Nevada and Arizona, reached drastically low levels in the summer of 2022. However, water levels have since started to recover because of above-average precipitation and snowpack that melted throughout this year. As of Wednesday afternoon, its levels were at 1,065 feet, 20 feet higher than this time last year.

The water level likely won't increase much until next spring, when snow melts in the Rocky Mountains and flows into the Colorado River, which then feeds into Lake Mead. However, the previously drought-stricken reservoir could see another big leap in its water levels beginning in the spring, according to a snowfall map from the NOAA.

On Wednesday, the NOAA released a snowfall map from El Niño winters that showed the average change in a state's snowfall while in those conditions.

It is one of two climate patterns that greatly impact the Earth's weather. La Niña recently culminated in the spring, ending a multiyear period in which the pattern influenced the weather. El Niño started in June, and NOAA has identified it as having high odds of being historically strong.

The NOAA map shared on X, formerly Twitter, on Wednesday showed the average snowfall difference during El Niño winters from 1959 to 2023.

According to the map, typically snowy regions such as Michigan, northern Illinois, Wisconsin and Minnesota experienced 2 to 6 inches less snowfall when in an El Niño winter. The warm phase often leads to drier conditions in the north and wetter conditions in the south.

The map showed that western states like eastern California, Nevada, Utah, Colorado and Arizona received higher than average snowfall, with some areas receiving up to 10 inches more than normal.

The snowfall could make a big difference in Lake Mead's water levels. Rainstorms are beneficial to the reservoir's water levels, but the lake receives most of its water in the form of melting snow from mountainous regions, mostly the Rocky Mountains in Colorado, Utah and Wyoming.

Higher-than-average snowfall last winter bolstered the lake's levels throughout the summer, during a time when they typically fall due to high temperatures and little precipitation. Next winter could produce similar outcomes.

However, predictions aren't always accurate. For example, La Niña often leads to drier conditions during the winter for states like California, but that wasn't the case last winter when more than a dozen atmospheric rivers—vast airborne corridors of water vapor—flooded the state.

AccuWeather senior meteorologist Dale Mohler told Newsweek that their precipitation predictions were lower than the NOAA's map suggested for Arizona.

"Our winter forecast for Lake Mead is normal or below normal," Mohler said.

The reason for AccuWeather's hesitant precipitation predictions is a cool pocket of water near southwest California. A warmer pocket would suggest above-average precipitation.

However, Mohler said the Rocky Mountains could receive above-normal precipitation. which in turn would benefit Lake Mead.

"It's mostly a positive outlook, but we're a little more conservative with our precipitation totals," Mohler said.