Understanding the Vertical Slope and Maintenance Mechanisms of Mesoscale Snow Bands

Mesoscale snow bands are frequently responsible for dumping large amounts of snow over a relatively small region and pose a considerable forecasting challenge. The recently concluded NASA Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field campaign observed several instances of mesoscale snow bands during January and February of 2020, 2022, and 2023. These snow bands were sampled by a combination of airborne (NASA ER-2 and P-3) and ground-based remote sensing and in-situ instruments.

Along-band cross sections of these snow bands reveal that many of them are vertically sloped. Our analysis of the mesoscale snow bands observed on 5 February 2020 indicates that the vertical slope is not maintained by isentropic lift and does not appear to be tied to horizontal deformation at the location of the bands. A combined analysis of the reflectivity and wind retrievals from the ER-2 radars raises the possibility that these features could be produced by vertical wind shear layers deforming fall streaks into bands that extend hundreds of kilometers. Furthermore, the actual positioning of the banding features appears to coincide with regions of slantwise instability aloft in HRRR analysis fields. The present study will focus on extending our analysis to include additional cases and understanding the mechanisms that support these features using a combination of radar data, in-situ aircraft measurements, and numerical modeling.