69 Snowbands associated with standing waves in Colorado snowstorms

Wednesday, 20 August 2014
Aviary Ballroom (Catamaran Resort Hotel)
Russ S. Schumacher, CSU, Ft. Collins, CO; and S. Rutledge and P. Kennedy

During two Colorado snowstorms in March 2013, heavy banded snowfall was observed that appeared to have a wave-like structure. In particular, there was a region of apparent subsidence and suppressed snowfall in far northern Colorado, with a band of enhanced snowfall to its immediate south. These bands both occurred in an environment with primarily northerly winds at low levels.

Radar observations from the National Weather Service network and the CSU-CHILL radar, along with numerical simulations, demonstrate that a standing wave developed in the lee of the Cheyenne Ridge, an east-west ridge in southern Wyoming with an elevation change of approximately 300 m. In both cases, the simulations show a downward branch of the wave in the immediate lee of the Cheyenne Ridge, with an upward branch to its south. Heavy snow was generated within this upward branch and ultimately fell farther downstream, explaining the wave-like pattern in the observed snowfall accumulation in radar observations and at the ground.

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