220 Gap-Filling Mobile Radar Observations of a Snow Squall in the San Luis Valley

Thursday, 31 August 2017
Zurich DEFG (Swissotel Chicago)
Andrew A. Rosenow, CIMMS/Univ. of Oklahoma and NOAA/NSSL, Norman, OK; and K. W. Howard and J. Meitín

Handout (3.6 MB)

The Intermountain West of the United States is deficient in radar coverage to adequately observe mesoscale phenomena that impact the public and commerce. On January 24, 2017, a snow squall developed from convective snow showers moving off of the San Juan Mountains and through the San Luis Valley in southern Colorado. This snow squall occurred in a region with poor WSR-88D coverage and impacted the valley's commercial airport, with visibility dropping from 13 km to 1.2 km in five minutes. This study utilizes data from the dual-polarization, X-band NOAA X-Pol (NOXP) radar deployed in Alamosa, Colorado, as part of the Upper Rio Grande Radar Project.
The snow squall evolved as the convective cells grew upscale into a linear convective system in an environment with surface-based CAPE values near 500 J kg-1, as diagnosed by the High Resolution Rapid Refresh (HRRR) model. The line propagated along an instability gradient, instead of purely being advected by tropospheric flow. The snow squall displayed structures typical of linear convective systems, including a sharp leading-edge reflectivity gradient, surging outflow with Vr values up to 15 m s-1, and convective initiation along the gust front.
This study describes the life cycle of the snow squall as observed by NOXP and the environment conducive to its formation of the snow squall is examined. Finally, the data from NOXP are integrated into the Multi-Radar Multi-Sensor (MRMS) radar mosaic to illustrate the capability of merging data from gap-filling radars with the WSR-88D network in areas of complex terrain to produce a more contiguous observation of mesoscale phenomena important to regional forecast and warning requirements.
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