P48 Snow-rain transition regions under a warmer climate in the southern Canadian cordillera

Almonte, Juris, and Ronald Stewart, University of Manitoba, Canada

Rain-snow transition regions occur within almost all cold season storms affecting the southern Canadian Cordillera, highlighting the need to better understand these changing regions under a warming climate. The high-resolution CONUS downscaling dataset (Liu et al. 2016) is used to address this issue from January to April of 2010 which coincides with the period of the 2010 Winter Olympics. In this study, a transition region is defined at the surface as the accumulation of both solid and liquid precipitation above traceable amounts within the same hourly time-step. Transition regions were common over this period as exemplified by the event on 11-12 January during which a site on Whistler Mountain B.C. had 11 hours of transition regions with one lasting 5 hours. The average hourly transition region coverage was reduced by 30% from 14,917 km2 (3.7% of the study area) to 10,656 km2 under PGW. Under PGW there was a mean elevation gain of almost 300 m, and a spatial change from the Coastal Mountains to the higher Rocky Mountains. Even though the overall transition region area was reduced under PGW, there were more areas experiencing both lower (<2 mm/h) and higher (>6 mm/h) precipitation intensities.