La Niña: What it Means for the Sierra Nevada Snowfall

La Niña: What it Means for the Sierra Nevada Snowfall

La Niña is a cold event. Historically speaking, it’s brought massive amounts of snow to our area with cooler than normal temperatures keeping the snow pack around. (That might be good or bad depending on your feelings about cold wet weather.) It has also brought disappointment in the past as a weak La Niña system (2011-2012) initiated the first year of the record breaking California drought. NOAA forecasters have determined this upcoming season to be a strong La Niña year. 

What is La Niña?

La Niña is identified by cooler than normal water in the east-central Equatorial area of the Pacific Ocean. This is caused by stronger than normal Trade Winds pushing warm water westerly towards Australia and Indonesia creating a void, which is filled with cold water along the east-central Equatorial Pacific. For a visual explanation visit oceanservice.noaa.gov/facts/ninonina.html.

What Does La Niña Cause?

This cooler water in the east-central Equatorial Pacific pushes the Pacific Jet Stream and Polar Jet Stream farther north creating dry and warm conditions in the southern United States, while the Pacific Northwest is cool and wet. Below you can see a generic model of a normal La Niña weather pattern. We have already seen this pattern in affect with snow in the Rocky Mountains and in the Great Plains area. Snow in our area will greatly depend on variability in the Polar Jet Stream to drop lower and bring wet weather with it.

A Look Back at La Niña Past

Looking at the past La Niña years and what they did for the Sierra Nevada meant finding which years were moderate or strong; a weak La Niña system yielded little for our slopes. Below is a table of snow base totals by month from December to March of La Niña years from 1973 to 2011 of the Tahoe area on average.

Data from wunderground.com

What's Next?

For now, we are just going to have to wait for Mother Nature to do what she does best. Accuracy in future casting isn't a sure thing and as we can see from the La Niña snow depth table, each year was radically different from the other making it hard to predict anything. We are a hopeful bunch and we believe we will see a benefit to our ecologic and economic systems in the Sierra Nevada this winter.