Saturday, March 9, 2013

Upslope Slop in Colorado

As predicted, a typical upslope snowstorm is underway in Metro Denver.  Most common in March and April, these storms develop when the central low pressure of a Pacific system passes south and east of our region, sweeping Gulf moisture counterclockwise and "uphill" toward the Front Range.  As the air is forced to rise across the High Plains, Piedmont, foothills and mountains, it cools below its dew point and, depending upon the air temperature, precipitation falls as rain or snow.  The highest snow totals in Denver generally result from storms that move east along the Colorado-New Mexico line, producing an upslope flow from the northeast.

Today's storm is centered over western Kansas and our wind direction is more from the north, reducing the snow potential.  In addition, the air temperature is hovering in the low thirties (F),  producing a heavy, wet snow that is melting on our roadways (still warm from recent mild, sunny weather).  As a result, the storm has created a scenic but sloppy landscape; of the 8-10 inches that are predicted for Metro Denver, half will likely melt before colder air sweeps in overnight.

Then again, winds are expected to pick up this afternoon and blizzard conditions are likely to develop across the High Plains of northeastern Colorado and neighboring States as the system moves off to the east.  Its gift of copious moisture is surely welcome in this semi-arid environment, especially since we remain in a prolonged drought and sunny, warm weather is forecast for the coming week.  Such is the spring weather pattern along the Colorado Front Range: upslope snowstorms sandwiched between periods of mild, sunny weather.