An Observational Study of Snow Ratio Evolution in North American Midlatitude Cyclones

There is major importance in accurately predicting snowfall, yet this remains one of the most difficult aspects of meteorology. In addition to quantitative precipitation forecast uncertainties, large inter- and intrastorm variability contributes to the difficulty in a snowfall forecast. The goal of this project is to determine whether large scale changes of the snow-to-liquid ratio (SLR) exist within midlatitude cyclones in the Central Plains as they develop, mature, and dissipate. In order to do this, ten case studies of SLR evolution within midlatitude cyclones will be performed from which the relationships between SLR and local atmospheric conditions will be determined. This project hypothesizes that as midlatitude cyclones emerge from the Rocky Mountains and move northeastward, the SLR will decrease. To test this hypothesis reanalysis data and 6-hourly observational snowfall data, obtained from the River Forecast Center (RFC), will be used. Because typical snowfall data is reported every 24 hours, it has been generally difficult to evaluate SLR changes within a single cyclone. However, due to the small temporal resolution of the RFC data, this project will be able to evaluate SLR evolution.