Climate impacts on sporadic winter storms and rising temperature in the Sierras

This last weekend we saw the largest storm to hit the Sierras this winter. The Central Sierra Snow Lab measured 75.2 inches of new snowfall over a four day period ending March 4.

So what does this mean in terms of snowpack, drought, and how our wildfire season will pan out? And how does this align with climate and precipitation trends for us in Northern Nevada? As a climate researcher in the Western Regional Climate Center at the Desert Research Institute, this is exactly what my lab focuses on.

We are currently in the midst of an “interesting” year, meteorologically speaking. We are in the middle of a strong El Niño winter, and this year will likely be in the top five strongest El Niños since 1950. 

A common misconception is that El Niño years are wetter than most in the Sierra Nevada, considering the phenomenon stems, in part, from oceanic weather patterns. But this is not always the case. The strongest El Niño on record was in 2016, leading to exceptionally dry conditions in Southern California and a near average year in the Sierra. Prior to the storm last weekend, the Sierras were at about 75-90% of the average snowpack for this time of year. After the storm, the northern Sierra snowpack is at 114% of average, central Sierra at 101% of average, and southern Sierra at 92% of average.

Our water table has been shaping up to be somewhat typical for the year, averaged across the state. It is even above normal in many parts of southern Nevada and California where we witnessed high flooding in places like San Diego and Las Vegas. 

Although this winter has not seen anywhere near the precipitation we had last winter, our water reservoirs are buffered from last year’s huge winter, reducing supply concerns and surface water drought issues. We entered into this past December with most of Nevada’s surface water supply in good standing (with the exception of Lake Mead). We even saw that overall drought had dissipated in Nevada and California, according to the US Drought Monitor. 

But one thing we haven’t seen in the 21st century is an extended wet period that lasts for more than two years in a row. The most recent example in the Sierra was the four year period from 1995-1998 with above-normal precipitation during all four water years. Prolonged wet periods also occurred in the 1970s and 1980s. Since 2000, we’ve had more whiplash years, with some of the wettest and driest on record in the last ten years alone, but not forming consecutive trends.

We do, however, see a continuous trend in our higher-than-average winter temperatures due to our changing climate. This year is right in line with the trend we have been seeing over the past few decades (it was the 12th warmest winter on record for the Sierra since 1895), even with last year being a true anomaly for cold-staying winter storms. This includes spring heat waves, which in turn impact snowpack and water run-off. 

This year, we will have to wait and see what March and April showers bring to understand the full impact on summer water tables and wildfires, although this last storm definitely added to our snowpack supply. When we don’t have enough snowpack at higher levels, we are concerned with how it will impact drought and the water table. At lower levels, there are more concerns around wildfires.

We also know that when the ground stays wetter longer, this can be a double-edged sword. On one hand, it can create more resiliency against timber fires. On the other hand, it can create fertile environments for the propagation of wildland fine fuel substances, such as cheatgrass.

As researchers, we need to continue to explore the long-ranging impacts of climate issues to best predict outcomes and find solutions. As we continue to build resiliency in communities affected by climate change, it’s good to see agencies like the National Oceanic and Atmospheric Administration (NOAA) receive funding to do just that from the Inflation Reduction Act, which invested $3.3 billion. This funding specifically addresses how to best prepare, adapt, and build resilience to weather and climate events in the US. 

We must continue to best understand our environment so we can drive data-based decision-making for our regions and the places we love most.

The views expressed are the author’s own and do not necessarily reflect the opinion of DRI or the Nevada System of Higher Education.