(COLORADO) — For an extremely rare third year in a row, a La Niña weather pattern is set to take hold of Colorado this winter.
To put it into perspective, there have only been two other times in the past 72 years when this triple-dip La Niña has happened. A recent study by Advancing Earth and Space Science highlights how rare this is and why this pattern is becoming more common in the western U.S.
So how exactly does La Niña impact us during the winter season? This pattern leads to drier and warmer-than-normal weather in Southern Colorado. However, northern parts of the state see a better chance for snow in the winter forecast.
Looking back at snowpack across Colorado during the past La Niña years shows how this pattern brings much more variability to the mountains. Some years have even brought above-average snowpack to the high country; it just depends on what winter weather systems make it into northern Colorado.
La Niña is a weather pattern where we see a temporary cooling of ocean surface temperatures in the Pacific Ocean, and a small change in the ocean’s temperatures has a big impact on our weather.
Winds along the equator push warm water west, allowing colder water to rise up to the surface. The effects are strongest during the winter when the jet stream sinks over the country.
This causes colder temperatures in the Pacific Ocean, limiting rain clouds and cooler weather across the southwestern U.S. The pattern also favors colder and stormier weather across northern parts of the country.
Typically, La Niña events occur every 3 to 5 years, which goes to show just how unique seeing this pattern for a third year straight is.
The Climate Prediction Center expects La Niña to be strongest through December, with the pattern possibly breaking down in early 2023. Forecasts call for a 91% chance of La Niña conditions through November, dropping to a 54% chance January-March.
This triple-dip La Niña will be most harsh this winter across the West, especially California, where they get most of their rain during the winter. December through April is typically when California gets most of its rain, but La Niña calls for a dry winter for the state.
Parts of California, the Desert Southwest and Pacific NW are still under the most extreme drought categories in early October.
Beneficial rains in Colorado have continued to chip away at drought conditions, with a quarter of the state completely drought-free. Only about 4% of Colorado is under extreme and exceptional drought conditions.