Abstract
Interpretation techniques are established which relate heavy snow (100 mm or more in a 12 h period) areas to real-time infrared and visible geostationary satellite imagery. An initial collection of cases totaled about 75 during the period from the fall of 1979 to the spring of 1984. The main area of concern extended from the Rockies to the Appalachians.
By using conventional surface and upper air data and numerical model output from the LFM-II relationships were established between heavy snow occurrences and cloud patterns in the satellite imagery. The different cloud patterns and flow regimes suggest a classification of heavy snow events into four main types: High Plains cyclogenesis, northwest and southwest flow short-wave troughs, and orographic. Each type has preferred geographical locations, common snowfall durations, storm totals, and band widths and lengths. The snowfall maximum with each storm is influenced by the strength and movement of the system and the structure of the moist layer. Subtle mesoscale features on the satellite imagery are shown to relate to the local snowfall maximum.
Real-time analysis and forecasting techniques are discussed. The heavy snow threat is assessed by a three-step analysis method. An example demonstrates how future trends in heavy snow can be predicted.
