Analysis and Simulation of a Winter Storm over Utah

Abstract

The evolution of a major winter storm over Utah during 6?7 January 1992 is analyzed using surface and upper-air observations and satellite imagery. A mesoscale model is used to deduce the dynamical processes that took place during the storm. Output from the Nested Grid Model of the National Meteorological Center is used to specify the initial conditions and the lateral boundary conditions of the mesoscale model. Two numerical simulations that each last 12 h in duration are studied here. The first begins at 1200 UTC 6 January, while the second starts at 0000 UTC 7 January. Attention is placed on a secluded zone of warm, moist air that is located along the northern and western boundaries of the midtropospheric cyclonic circulation as it moved across Utah. Output from the second mesoscale simulation is used to explain the processes by which air in the secluded zone is lifted. These processes include large-scale ascent west of the cyclonic circulation aloft, lift provided by a shallow cold front, and orographic ascent as the low-level flow encountered the mountain ranges of western Utah.