Weather packs a wallop
EAGLE – You know the usual weather in the Eagle Valley. When brooms suffice to scuttle the snow in Gypsum and Eagle, people in the upper valley are calling in the plows. The higher the elevation, the more punch from snowstorms.The snowstorm just after Thanksgiving was something different – by no means unique, but certainly rare. From Gypsum to Vail, the snow depths were about the same. Even more rare are those storms that dump on the lower valley, but leave barely a skiffle in the valley’s more lofty precincts.Why the difference? Mountains explain most of our weather patterns.
When blowing in from the west, most storms must work to rise when confronting mountain barriers, something called orographic lift. After pausing to drop snow and rain, they move on. Places downwind from the mountain barriers get little moisture, something that is called the rain-shadow effect. That basic principle explains why Eagle and Gypsum, located in the shadow of the Flat Tops, tend to be dry, while Vail, nestled amid the Gore Range, more often gets drenched.Temperature differences also explain why higher elevations generally get more snow, explains Jim Pringle, a forecaster with the National Weather Service in Grand Junction. Typically, the higher the elevation, the colder the air temperature. Because colder air usually can hold less moisture, that means the higher mountains get more snow than the valleys.
Records kept for several decades at the Eagle County Regional Airport show an average precipitation of 7 inches per year, compared to 22 at the golf course in Vail, and 40 inches and more on Vail Mountain, and other locations in the Gore Range.But what explains the man-bites-dog weather patterns, the storms that leave as much, or even more, snow in Eagle than in Vail? Something called dynamic lift is at play. Instead of mountains forcing precipitation-laden storm fronts to rise, an intense, low-pressure system that extends from the surface to 30,000 feet will force the storms to rise.That’s what happened in the snowstorm after Thanksgiving. A mass of cold air, parallel to the jet stream, snaked from Eagle toward Kremmling, and then to Grand Lake. That created the anomaly of Green Mountain Reservoir getting more snow than Breckenridge. Although 1,700 feet lower in elevation, Kremmling got more snow than Winter Park.
Another example of this dynamic lifting is when masses of cold air settle into lower valleys. When this happens, Gypsum can be much colder than Vail. In some cases, this mass of cold air can create the equivalent of a bulky mountain. When these storms arrive voila, it’s time to break out the big shovels in Eagle and Gypsum.That’s essentially what occurred in February, 1989, when Vail and Beaver Creek first hosted the World Alpine Ski Championships. A mass of Arctic-cold air moved into Colorado, west of Craig. As it did, moisture-laden air bumped up against the cold air, and blanketed the sagebrush-covered lowlands around the town of Maybell.Next, the Arctic mass of air sidled into the White River Valley, near Meeker, and again, the valley bottom got buried in snow, while the highlands got little. Then, the cold air crossed the Flat Tops and into the Colorado, and then the Eagle River Valley. It was brutally cold, and the snow was plenty deep – but just as deep in Eagle, at an elevation of 6,600 feet, as it was on the race course at Beaver Creek, at 8,000 to 10,000 feet.Vail, Colorado