Convective snowbands downstream of the Rocky Mountains in an environment with conditional, dry symmetric, and inertial instabilities

The simulated bands occurred in an environment with a nearly well-mixed, baroclinic boundary layer, positive convective available potential energy. and widespread negative potential vorticity. Individual bands initiated on the low-momentum side of vorticity banners downstream of mountains, and in association with frontogenetical ascent along two baroclinic zones. In addition, ascent caused by both frontogenesis and banded moist convection produced additional narrow regions of negative vorticity by transporting low-momentum air upward and creating strong horizontal gradients in wind speed.

This event is similar to other observed instances of banded convection in the western United States on the anticyclonic-shear side of strong mid- and upper-tropospheric jets in environments lacking large-scale saturation. In contrast, these events differ from previously published banded precipitation events in the comma head of extratropical cyclones and downstream of mountains where large-scale saturation is present.