A climatology of cold air outbreaks in Montana

A 34-year climatology of winter cold air outbreaks (CAOs) was developed for 14 NWS surface observation sites in Montana, based on hourly and daily temperature records during the period 1973-2007. CAO occurrences were subjected to a variety of surface temperature thresholds that were at least one standard deviation below the average winter low temperature. This was done to examine the interannual variability of winter CAOs relative to those temperature thresholds. A weak relationship was found between the frequency of CAOs in Montana and the large scale pattern present, including synoptic scale features and modes of global teleconnection patterns.