DENVER (CBS4) – A report released Thursday from the Climate Prediction Center and the International Research Institute for Climate and Society said the upcoming winter season could feature a La Niña weather pattern for the United States. The report showed a 66% chance that La Niña would emerge sometime between September and November. If it develops forecasters say that it would last until the spring of 2022.
La Niña is a cooling of the surface waters in the east-central part of the Pacific Ocean near the equator. The strength of La Niña determines how it’ll influence weather patterns around the globe.
You may recall that we experienced a moderate La Niña this past winter in Colorado. Seeing two consecutive winters with a La Niña is actually quite common when looking at the data since 1950.
When La Niña develops it tends to position the main branch of the Polar Jet Stream to the north of Colorado. This gives states along the Canadian border a higher-than-normal chance to be cool and wet. Southern states often end up with a higher-than-normal chance to be warm and dry which can lead to the development or expansion of drought.
Colorado is usually caught in between the wet and dry. Northern Colorado is often windy during a La Niña winter and they tend to see the most consistent chances for snow because they are closest to the storm track. It can be the total opposite for southern Colorado. Because our state is so large and has such complex terrain it’s hard to make a precise forecast for a La Niña winter.
Here’s something we do know from history. When part of Colorado is already in a drought as a La Niña winter begins, the drought can worsen due to the absence of the jet stream. Right now western Colorado continues to deal with extreme to exceptional drought in many areas. We’ll need to see many days full of soggy, monsoon thunderstorms over the next several weeks to see any type of improvement before the arrival of winter.