Denver's Upslope Snowstorms

While meteorologists are very knowledgeable about atmospheric conditions and storm dynamics, I have found that they sometimes overlook the effects of landscape topography when making their forecasts. Just over the past month, national weather forecasts were inaccurate on several occasions when it came to snowfall in Denver.

Metro Denver sits at the southwest end of the South Platte Valley and is surrounded by higher terrain to the west (the Front Range) and to the south and east (the Palmer Divide and associated High Plains); there is also a ridge of higher terrain just north of the city. As a result, winds blowing into the region are downsloping from all directions except the northeast; since air warms and dries as it sinks, this topography is responsible for Denver's mild, dry, sunny climate.

And, contrary to its perceived image as a winter ski resort, most of the city's snowfall occurs in March and April, when Pacific storms cross the Rockies, pull moisture from the Great Plains and push it westward (and upward) toward the Front Range; these upslope snowstorms occur across all portions of Colorado that lie east of the Continental Divide. However, for Metro Denver to receive significant snowfall, the upslope must come from the northeast, causing air to rise and cool as it moves up the South Platte Valley. Storms that produce this pattern are generally centered over southeast Colorado or along the New Mexico-Colorado border; when the central low is further north, most of the snow falls across northeastern Colorado, Wyoming and the northern Front Range while storms south of the New Mexico border produce heavy snow across the Palmer Divide, southeastern Colorado and the Sangre de Cristo mountains.