Microphysical Processes within a Heavy Mixed Precipitation Band in the 16–17 January 2022 Winter Storm

Mesoscale snowbands within extratropical cyclones cause major societal disruptions in the Northeast U.S. and are challenging to predict. Previous literature has suggested the importance of mid-level frontogenesis in primary snowband development northwest of the surface low. However, little is known about the coupled microphysical and dynamic processes within these primary snowbands. In this study we examine the 16–17 January 2022 winter storm, where a frontogenetical circulation interacted with a near-freezing thermodynamic profile to produce a heavy mixed precipitation band over western NY. Microphysical analysis for this case uses data from the University of Illinois System for Characterizing and Measuring Precipitation (SCAMP), a multi-sensor suite of instruments deployed in Buffalo, NY. Data from the NOAA P-3 aircraft during the NASA Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS) field project also helped identify precipitation characteristics. In order to further investigate the small-scale terrain influences on the low-level thermodynamic profile, output from a Weather Research and Forecasting (WRF) model simulation with 1-km grid spacing is analyzed.

Observations within the mixed precipitation band from the SCAMP vertically-pointing Micro Rain Radar-2 reveal equivalent reflectivities of 30–40 dBZ and fall speeds nearing 4 m/s. Additionally, particle size and fall speed distributions from the SCAMP show melting snow as the predominant precipitation type, suggesting aggregation was likely occurring. Cross-sectional analysis from the WRF model depicts the dynamical processes and resultant thermodynamic environment affecting the microphysics. An area of persistent low-level sinking downwind of the higher terrain in western NY was co-located with a warm nose and above freezing temperatures. This low-level sinking initially developed from orographic gravity waves and became enhanced as the frontogenetical circulation translated northwest. Overall, preliminary results show the low-level sinking motion, in part due to the frontogenetical circulation and terrain effects, may have played an important role in snow particle melting, aggregation, and consequently, the intense snowfall rates observed during this storm.