Front Range Snowstorm

It's not easy to predict the intensity of Front Range snowstorms.  Many factors come into play, including the temperature and humidity of the air, the potency of the storm, the track of the central zone of low pressure (which determines the direction of the upslope flow) and the speed of the system as it crosses our region.

Contrary to public perception and the simplistic comments of TV weather forecasters, storm systems move in from the west but "snowstorms" do not.  The latter must redevelop in concert with the factors mentioned above.  While some moisture may move in from the southwest or northwest, the majority of the precipitation is "wrung out" by the Continental Divide; snow that falls along the east flank of the Front Range (and along the Front Range urban corridor) depends on upslope flow from the Great Plains.  Since Denver sits in the South Platte Valley and is nearly surrounded by higher terrain, intense snowstorms in the city depend on the generation of an upslope flow from the northeast (up through the South Platte Valley).  Subtle changes in the direction of the storm track (and thus of the upslope plume) can dramatically affect the snowfall in Metro Denver.

Last night, when I went to bed, a few flakes were in the air; according to the Weather Channel and local forecasters, we were expected to receive 2 to 5 inches of snow overnight.  This morning I awoke to find 10 inches of powdery snow coating our Littleton farm; as I write this post, more than six hours later, it's still snowing!