This summer in Colorado was the driest on record. But forecasters say weather patterns during the hotter months aren’t a predictor of what winter might bring.
“Just because you have a dry summer does not necessarily mean you’re going to have a dry winter,” said Michael Charnick, a meteorologist with the National Weather Service in Grand Junction. “There are a lot of factors that go into it.”
Charnick said overall, the Roaring Fork Valley may see slightly above-average temperatures and slightly below-average precipitation.
To make longer-range weather predictions, forecasters look to changes in ocean temperature that can shape storm patterns over North America. This winter, they are considering the effects of “La Niña,” a weather phenomenon that starts with cooler water in the eastern Pacific Ocean off the coast of South America.
“It has a greater effect in some regions,” said Thomas Horner, founder of Colorado-based forecasting website Highpoint Weather. “In Colorado, we sit in the middle of climatic impacts. In Colorado, the effects are very noisy and not very pronounced in terms of impacts on our weather.”
Past La Niña years have been varied, according to Horner. Colorado has experienced some of its driest winters and some of its snowiest winters during La Niña years. In decades of combined data, northern Colorado tends to see more snow during those years, while southern Colorado gets less. La Niña tends to mean roughly average precipitation for the Roaring Fork Valley, which sits between those two regions.
Horner says Colorado snowpack totals are often dictated by only a handful of big storms, which could come as a result of La Niña bringing wetter weather to the region.
“We have slightly better chances of having a little more snow in northern and central Colorado this winter due to La Niña,” Horner said. “We’ve seen years that are way above average and way below average. It just means we have a slightly greater chance of perhaps picking up a good storm or two that could give us an above average snowpack.”
La Niña is considered a “temperature anomaly,” but climate change means that weather experts have had to adjust their definition of “anomaly” because warmer anomalies have been happening more frequently in recent years.
Climate change, including shifting temperatures and impacts to the jet stream, will likely change the frequency and location of snowfall.
“Besides just temperatures it’s caused large-scale changes in weather patterns, which can cause long periods of dry weather regardless of temperature,” Horner said.
He adds that climate change’s impacts are complicated, but generally do not look good for the volume of Colorado’s snowpack. Snow will only fall at higher elevations and begin to melt earlier in the spring, meaning snowpack will have less depth and longevity.