Evidence of Ascent in a Sloped Barrier Jet and an Associated Heavy-Snow Band

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  • 1 NOAA/NWS Western Region, Scientific Services Division, Salt Lake City, Utah
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Abstract

Doppler radar data are used to identify alongstream slope of a barrier jet running parallel to the cast slope of the Front Range of the Colorado Rockies. The barrier jet was collocated with a narrow band of heavy snow embedded within a larger area of light-to-moderate snow. The conditions responsible for the formation of the barrier jet are shown to be a sloped inversion associated with a recent cold-frontal passage. This resulted in a situation similar to those observed in cases cold-air damming. The slope of the barrier jet indicates ascent of air parcels in the jet of 0.18 m s−1and this vertical motion is proposed as the mechanism for the heavy-snow band observed in the radar data. This is in contrast to conceptual models associated with cold-air damming that depict enhanced precipitation due to ascent of air above the sloped inversion.

Abstract

Doppler radar data are used to identify alongstream slope of a barrier jet running parallel to the cast slope of the Front Range of the Colorado Rockies. The barrier jet was collocated with a narrow band of heavy snow embedded within a larger area of light-to-moderate snow. The conditions responsible for the formation of the barrier jet are shown to be a sloped inversion associated with a recent cold-frontal passage. This resulted in a situation similar to those observed in cases cold-air damming. The slope of the barrier jet indicates ascent of air parcels in the jet of 0.18 m s−1and this vertical motion is proposed as the mechanism for the heavy-snow band observed in the radar data. This is in contrast to conceptual models associated with cold-air damming that depict enhanced precipitation due to ascent of air above the sloped inversion.

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