A case study of heavy snowfall in Oklahoma

Heavy snowfall occurred in central Oklahoma on 14 December 1987. The snowfall continued throughout the following day, with over 30 cm of snow falling from Oklahoma to Michigan. The snow in Oklahoma fell from a warm-frontal snowband that was oriented northeast-southwest. An objective analysis of the synoptic-scale data indicated that frontogenesis was present in the warm-frontal region and a direct circulation pattern around the warm front. The ageostrophic winds above the warm front forced the conditionally unstable air to ascend and release its instability. The forcing mechanisms for the snowband were, therefore, frontogenetic forcing and convective buoyancy. A series of plan position indicator volume scans were obtained with the NSSL Doppler radar at Norman, Oklahoma. Single-Doppler analysis techniques were used to calculate the mesoscale kinematic properties of the snowband. The data from a special rawinsonde released within the band was combined with the radar-derived kinematic structure to reveal the mesoscale thermodynamic structure of the band.