An Improved Environmental Forecast Parameter for Snow Squalls in the High Plains and Mountain West PDF Download

Author: Robert Capella
Publisher:
ISBN:
Category : Airports
Languages : en
Pages : 35

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Book Description
The National Weather Service (NWS) has been issuing snow squall warnings since the winter of 2018-19. Snow squalls are intense but brief periods of moderate to heavy snowfall accompanied by high surface winds resulting in reduced visibility and dangerous white-out road conditions. Model guidance must be a key supplement to observations in issuing snow squall warnings, especially in the High Plains and Mountain West, due to the relatively sparse radar network for snow squalls, beam blockage by terrain, and coarse surface observation network.In this study, we analyze five cool seasons (Sept-May, 2016-2021) of surface-observed snow squalls at the Cheyenne Regional Airport (KCYS) in Wyoming. Our definition of snow squalls is aided by an online survey completed by NWS forecasters in the High Plains region. A climatology of 56 observed snow squall events is built and evaluated for common synoptic and mesoscale traits. It is found that snow squalls are driven by shallow upright convection (either surface-based or elevated) and/or by localized dynamical forcing (symmetric instability and/or frontogenesis).Given the small scale and convective nature of snow squalls and the complex terrain in the region of interest, the convection-permitting High-Resolution Rapid Refresh (HRRR) model is used. We leverage the cases’ and control’s modeled environments to assess the skill of the Snow Squall Parameter, developed based on New England snow squalls, and a new EPV-based forecast parameter against known events. We find that the latter better predicts the environment which can support snow squalls in the High Plains and Mountain West.