The Role of Frontogenetical Forcing and Conditional Symmetric Instability in the Midwest Snowstorm of 30–31 January 1982

Abstract

Abstract On 30-31 January 1982 a modest low pressure system moved through the lower Mississippi Valley into western Tennessee. During this 24-hour period rain changed to snow over central Missouri and Illinois, increasing in intensity over the last 12 hours, In addition, embedded convection took place over east-central Missouri- Illinois including the St. Louis metropolitan area. Overall snow totals were over 25 cm within a narrow band along the edge of the precipitation shield. Frontogenetical forcing together with conditional symmetric instability are discussed as possible physical explanations for the intense precipitation which was not well forecast. It is shown that moderate-strong ascent was part of a thermally direct ageostrophic circulation created by frontogenetical forcing. Frontogenesis is shown both at the surface and aloft to increase in the 12 hour period prior to the heavy precipitation. It is strongest in the low levels and slopes to the west-northwest with height along an advancing cold f...