Perhaps this year more than others, it seems that Coloradans are ready to put the spring, summer, and fall of COVID-19 behind us and look to brighter, snowier days ahead. While we still don’t know exactly what the ski season will look like in light of the ongoing pandemic, we can somewhat predict the winter forecast by looking at some known weather patterns.
ENSO, or El Niño Southern Oscillation, is a climate pattern based on the water temperatures of the equatorial Pacific Ocean. There are three different phases of ENSO; El Niño, warmer than average water temperatures; Neutral, average water temperatures; and La Niña, colder than average water temperatures. Currently, we are in a La Niña phase, which is forecast to last through winter and into spring 2021. In a typical La Niña year, the jet stream tends to flow down from the Pacific Northwest area, through the northeast corner of Colorado and into the Tennessee Valley before curving up and over the northeastern United States. The jet stream is largely why storms move from west to east, so we can infer that this winter, most storms will track near and to the north of us.
All La Niña years are different, and there is no direct correlation on how a La Niña setup impacts Colorado, but there are generalizations that can be made. In a normal La Niña setup, southern Colorado typically ends up seeing a drier than normal winter; elsewhere, it’s a little harder to pin down specifics.
For the Front Range, the best way to forecast this upcoming winter is to look at previous winters where La Niña was present. That brings us to the winter of 2017–18. Denver averages about 56 inches of snow per season, but during the 2017–18 winter, Denver picked up 25.7 inches—the fifth-lowest total in the city’s history. The prior winter, 2016–17, was also a La Niña year, and Denver totaled just 21.8 inches of snow—the second lowest snowfall total in the city’s history. Moreover, 18 of the last 22 La Niña winters have produced less-than-average snow for the Mile High City.
This doesn’t mean we are guaranteed to have a below average snowfall season, but the numbers are rather strong. In regard to the the snowpack in the high country, there is no concrete evidence showing how it is impacted, but the La Niña wind direction and topographical forcing tends to create good snow setups for the central and northern mountains at times.
Now, if you’re a snow lover, not all hope is lost: The Farmer’s Almanac says that Colorado will get more than enough snow this winter. It suggests we should be on alert for a big November storm and a string of storms in February. The Farmer’s Almanac started back in 1818 and makes predications based on their original weather prognosticator, which takes into account sunspot activity, planetary positions, and the effect of the moon has on Earth. While at times the Farmer’s Almanac may end up being correct, their forecasts are more of a guess than an actual meteorological forecast, so take what you read there with a grain of salt.
Regardless of what happens, we desperately need any kind of wet weather to help our current and expanding drought. Winter rains and snows are usually good drought-busters, but this year, timing may not be on our side.