Is the California drought over?

The California rainfall season begins July 1 and ends the following June 30. Most other stations, including Coeur d’Alene, begin their moisture season Jan. 1.

Thanks, at least in part, the warmer-than-normal sea-surface temperature event, El Niño has helped to produce the recent very heavy rainfall across Southern California and parts of the Desert Southwest. Another big batch of rain is expected to move across Southern California early in the week which will likely produce more area flooding.

One of the reservoirs in this part of the country that has been watched closely in recent years is Lake Mead, located on the Arizona and Nevada border. This is a man-made reservoir for Hoover Dam and supplies critical water supplies and hydroelectric power to millions of people in Southern California and Arizona. Rapid population increases and long-term droughts have contributed to the fall of the lake’s level to a level of great concern, especially in recent years.

Lake Mead’s current level stands at just over 1,047.5 feet. The lowest level for Lake Mead was 1,041.30 feet July 28, 2022, which was only 27% of total capacity. Since that time, the lake has risen to approximately 1,076 feet, an increase of 35 feet.

The rise of one of the most important reservoirs in the country is good news, but the levels are still a whopping 150 feet lower than they would be at full capacity. Despite the recent heavy rainfall, the lake stood at about 37% of capacity as of the weekend. With the expected moisture this week, it’s very possible that the lake level will eventually rise to over 40% of capacity.

Moisture totals across Southern California are more than double the normal as of the weekend. Despite the floods, the rainfall has been helpful as it eased the drought crisis, added some temporary relief from early fire seasons and provided critical moisture for fruit and vegetable crops.

Scientists say that one good rainfall year does not end decades of drought. In many instances, when there are periods of heavy rainfall at one time, the water will often overwhelm the dry soils as well as the systems created to contain the water. Instead, there are massive floodwaters that quickly move across landscapes and then run off into the sea. The best kind of rainfall is more of the “slow and steady” variety that will give soils a chance to absorb the moisture, plus help to fill the reservoirs more effectively.

As Southern California deals with the flooding rains, farther to the north in the Golden State, conditions have not been as wet. For example, Sacramento’s rainfall season which began last July 1 is slightly below normal to date.

As I mentioned last week, this very strong El Niño event has likely peaked and is now showing signs of weakening. Therefore, this massive El Niño may be coming to an end much sooner than later. Earlier this month, the U.S. Climate Prediction Center issued a report stating that El Niño has passed its peak, and conditions may be favorable for a new “La Niña,” the cooler-than-normal sea-surface temperature event later this year. In fact, the Climate Prediction Center is predicting that a new La Niña may form “within the next six months.” They are also forecasting a 55% chance of the La Niña developing from June to August and a 77% chance of formation from September to November.

Despite the recent moisture, a recent study published in Science says that much of the western U.S. and northern Mexico may be in an extreme long-term drought worse than any other one in recorded history. The research is based on modern weather observations and new tree-ring reconstruction data dating back over 1,000 years.

According to an article from Columbia, based on tree-ring data dating back to 800 A.D., there were four major megadroughts in the western U.S. These occurred in the late 800s, mid-1100s, the 1200s and the late 1500s.

Based on the tree ring data, all the “ancient megadroughts” were longer than 19 years and the one in the 1200s lasted for nearly a century. Other studies said that within the last 1,200 years, scientists claim that there were two dry long spells in parts of California each lasting for nearly 200 years. If a new La Niña forms later this year, then the odds of drier weather returning to much of California will be higher.

In terms of our local weather, the recent snowfall last week barely pushed Coeur d’Alene’s seasonal snowfall total to over 30 inches, which is well below the normal of approximately 57 inches. Additional moisture is expected this week, but once again, most of it is expected to fall as rain in the lower elevations.

As we get close to the Feb. 24 full moon cycle, there is the possibility of more snow across the lower elevations of the Inland Northwest. In early March, conditions are forecast to turn drier and warmer. Based on the effects of El Niño, the upcoming spring season is looking warmer and a little drier than normal across our region.

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Contact Randy Mann at randy@longrangeweather.com.