Justin and I spent the morning doing arial observations of most of the Yukon forecasting region. The overall goals for today were to assess spring conditions at a broad scale and to search for evidence of spring triggers such as cornices and loose wet avalanche triggering underlying persistent weak layers notably the Feb 21 SH and Dec 5 rain crust.
We finally got a refreeze overnight in the area with temperatures dipping down to -6C. Wind was light to moderate in the alpine and generally flowing from the SE. The highest temperature we recorded in the field today read 3.0C at about 1700m in the alpine. However, in the north facing bowl feature above this site, the skiing was quite good in 15cm of dry wind deposited snow on top of a supportive crust. This was in the Beaudette Creek area between the transitional and coastal snowpack areas.
Avalanche observations included numerous loose wet slides to size 2 at mid level elevations and at all aspects. Also, through the transitional snowpack area we observed numerous cornice failures to size 2. None of the these cornice failures had produced slab avalanches. Finally, we observed a few wet slab avalanches to size 3 on south aspects. These events had been triggered by smaller loose wet slides and the suspected bed surface was either the Dec 5 rain crust or the ground. I suspect the bed surface was indeed the December crust and the fact that we were now seeing dirt had to do with the age of these avalanches which are now 3 or 4 days old and what snow that remained after the event has now melted to ground.
Overall, fairly spring like conditions over the entire area. In the Wheaton Valley, south aspects are nearly bare and the snowpack in thinning rapidly. There is still some skiing to be had in the transitional snowpack areas but conditions are highly variable ranging from the snow described above to wind hammered crud like we found on Paddy Peak. Cornices seem to be much more active in the transitional snowpack area and I would suspect this is due to the more faceted nature of their bases in the colder, dryer region.
Please see next post for photos of the some of what is described above.
Widespread Cornice failure in Transtional Region.
More cornice failure
Widespread Loose snow avalanches on all aspects to size 2.0
More widespread wet loose snow avalanches.
Observed a few wet slab avalanches releasing on solar aspects in the Transitional/Coastal Snowpack regions.
Wet slab avalanches releasing on South Aspects.