High-impact Observations for Enhancing Great Lakes Snowfall Forecasting

Accurate forecasting of snowfall in the Great Lakes region is a difficult operational issue for the National Weather Service (NWS), as it is impacted by a variety of snowfall types, characteristics of which are influenced by the proximity to the lakes and often lead to extreme weather conditions. The Next Generation Weather Radar (NEXRAD) network enables valuable monitoring of snow events and provides critical quantitative precipitation estimates (QPE), but previous studies focused on the Great Lakes region indicate that prescribed reflectivity-to-snow-rate (Z-S) relationships may not correspond to ground-based observations of snowfall. Furthermore, Z-S variability exists between synoptically forced (system) snow events and lake-effect snow events, driven largely by microphysical variability.

To address this issue, we deployed key precipitation instrumentation to three strategic sites in the Great Lakes region through partnership with NWS Weather Forecast Offices in Marquette, MI, Gaylord, MI, and Buffalo, NY. The addition of profiling radars (MicroRain Radar2), disdrometers (Precipitation Imaging Packaging, Parsivel2), and snow gauges (Pluvio) can be synergistically combined with existing NWS assets, such as NEXRAD observations, meteorological measurements, forecaster observations, to assess Z-S relationships and improve QPE. We gathered two winter seasons (2021-2022 and 2022-2023) of enhanced observations to obtain retrievals of snowfall characteristics (e.g., snow rate, snow-to-liquid ratios, bulk particle densities, precipitation vertical structure) and we then leveraged these observations to assess radar derived QPE. We also examined case studies of extreme snowfall events, such as the unusually early-November 2021 event in Michigan, the mid-November 2022 event that impacted the entire Great Lakes region, and the deadly late December 2022 snow event that produced several feet of snow in Buffalo, NY. This strategic multi-location instrument deployment demonstrates the operational value of information-rich, snow-focused observations, anchored with the affordable and powerful coupling of video disdrometer and profiling Doppler radar instrumentation, to augment currently available NWS capabilities for winter weather forecasting and monitoring. Ongoing work will merge the observations from these deployments with surface flux measurements in the Great Lakes region and comparisons to Numerical Weather Prediction (NWP) model output of identified snowfall events.