Observed Precipitation and Weather Conditions across the Continental Divide in the Canadian Rockies

Major storms can lead to extreme flooding on the eastern slope of the continental divide in the Canadian Rockies. Precipitation can also reach the western flank of the continental divide when coming from the Pacific Ocean. As an example of this variability, the Kananaskis Valley, Alberta, Canada, can experience different types of precipitation when the precipitation events are travelling easterly or westerly. Extreme flooding events can occur when large-scale conditions are favorable for upslope precipitation, as during the June 2013 flooding event, which was the second most costly natural disaster in Canadian history. To better understand the processes leading to storms and precipitation in the Canadian Rockies, a field project was conducted on both sides of the continental divide during May and June 2019. Detailed measurements and observations of precipitation characteristics as well as their associated weather conditions were obtained at the surface and aloft. Results from the field project will be presented. First, the 19 storms documented are classified based on their synoptic scale conditions and precipitation types. Specific case studies are selected and the precipitation types are characterized using an optical disdrometer, a micro-rain radar, as well as micro-photography. For example, mainly rain was reported on the western side, whereas mainly snow and mixed precipitation on the eastern one. When rain was reported at the surface, the height of the melting layer is diagnosed and compared with the other side of the divide. Overall, this will allow us to understand the link between the weather conditions and the types of precipitation occurring on both sides of the continental divide.