Spatial and seasonal variability of the meteorological effects on avalanche potential in Colorado's mountain ranges

Snowpack conditions favorable for slab avalanche development are influenced by a complex interaction of meteorological and climatological elements. This study identifies the frequencies of weak layer development, snow loading events, and wet slab development. Temperature, snow depth, and snow water equivalent data is collected from SNOTEL stations across Colorado at elevations ranging from approximately 3,000 to 3,500 meters. SNOTEL locations are selected to represent common winter backcountry recreation areas in a plethora of regions across Colorado, in order to examine the variability in avalanche potential among Colorado's mountain ranges. Data from the period of 1993/94 to 2012/13 is examined. For weak layer development, the study is concerned with incidents of cold temperatures and shallow snowpack; assessed by counting the number of days, broken down by month, in which the temperature gradient of the snowpack is less than -10 degC/m. Temperature gradient is determined by dividing the average daily temperature by the daily snow depth. For new snow loading events, the study records the incidents in which the change in snow depth exceeds 15 cm, 22.5 cm, and 30 cm in a 48-hour period. Wind is a major loading factor as well; therefore, 700 millibar winds are examined and matched to new snow loading events. In the case of wet avalanche potential during the spring snow season, periods in which the average temperature exceeds 0 degrees Celsius for at least three consecutive days are examined. Finally, annual trends in avalanche potential, using the aforementioned criteria, are examined in order to identify any changes in the seasonal avalanche cycles that may be related to climate change.