The Snow Eaters

On certain winter days the Front Range performs a trick that feels almost like cheating against the season. A warm, dry wind comes pouring down the eastern slopes and a bitter cold morning can turn balmy within hours. These are chinook winds, a type of foehn wind, and the name comes from the Chinook people who lived near the lower Columbia River.

The mechanism is simple physics. Air rises over the mountains, drops its moisture on the western side, then rushes down the eastern slopes, compressing and heating as it falls. Locals have long called it the snow eater, and the nickname is earned.

A strong chinook can erase a foot of snow in a single day, partly by melting and partly by sublimating it straight into vapor. The temperature swings can be startling. The most extreme chinook on record happened just north of here in Loma, Montana, in January of nineteen seventy-two, when the temperature climbed from fifty-four below zero to forty-nine above, a swing of one hundred and three degrees Fahrenheit.

The fastest jump on record came in Spearfish, South Dakota, in January of nineteen forty-three, where the temperature rose forty-nine degrees in just two minutes. Along the Front Range the effect is usually milder but still dramatic, which is why a Denver winter can feel like several seasons crammed into one week.