Chester Lake Snow Observation Transect

Had an inauspicious start to the day. Sometime during the bleary eyed 6am transfer of gear to the carpool my ski boots remained behind the driver seat of my car. Not wanting to spend the day in the Chester Lake parking lot I decided to do a snow observation transect into Chester Lake, between elevations 1900m and 2300m. I did multiple hasty pits (4) on the hike in, and two study pits, one in Galatea Meadows on a 20 degree slope, and the other on the moraine at the end of Chester Lake, on a 30 degree slope. In both study pits I did both extended column compression tests across slope, and extended column propagation tests along the fall line. In my 30 years of climbing and skiing in the Rockies I have never experienced an early season snow pack like the one I observed today. The best phrase I can find to describe what I observed is "a total reset". At treeline, I found none of the growing dry facets and stiff wind slabs that are normal for this time of year. ***IMPORTANT WARNING*** do not try to cross Chester Lake, the surface is currently saturated, and not supportive.

Multiple wet slab storm releases ran to ground on the north facing aspect of the Mount Chester ridge, and on the south facing aspect of the Mount Galatea Gendarme. Based on snow cover, these appeared to have been triggered during the Tuesday through Thursday storm cycle; all originating out of steep terrain previously holding snow above threshold. The west most draw leading to the col on the regular scramble route up Mount Chester was cleaned out completely by a large, size 3, wet slab, originating out of step rocky leeward terrain on the west side of the draw. All the north couloirs on Mount Chester have been reset to rock and boulders. While multiple paths on the Mount Galatea Gendarme released to size 2, they had already been reloaded with cross loaded wind transport. Of concern is that the west most wind loaded south slopes above the Galatea Meadows have yet to run, as there was no evidence of debris.

At tree line we experienced broken clouds with scattered flurries, amounting to less than 1cm/hr accumulation of light small grained rounds and graupel. In the alpine above 2800m strong eastward winds over 60 km/hr were observed on Mountain Chester, with significant plumes and transport. All summits surrounding the Chester Lake basin were obscured by summit clouds, and high winds.

In all the hasty pits on the hike into Chester Lake (4), I observed the same pattern. The Tuesday to Wednesday warm storm decimated the existing snow pack into a 10cm water saturated layer, above this was another 20cm of wet crystals from the Thursday transition to snow, this is followed by a rapidly decomposing 5mm ice lens that must have formed on Friday before the most recent storm. The top of the snow pack is 10cm of fresh moist snow from the front that moved though Friday afternoon and night. The basal facets are completely saturated with water, and are decomposing rapidly; the Halloween crust could not be conclusively identified. I observed a similar pattern, but with nearly double the depth, at the study plots at Galatea Meadows, and the moraine at the back of Chester Lake. At the Galatea Meadows the uppermost layer was 10cm of moist storm snow sitting over the decomposing 5mm ice lens. This was followed by 30cm of wet crystals from the transition to snow on Thursday, and finally 20cm of decomposing saturated basal facets. At the Chester Lake moraine the uppermost layer was 20cm of moist storm snow sitting over the decomposing 5mm ice lens. This was followed by 40cm of wet crystals from the transition to snow on Thursday, and finally a 20cm mix of decomposing saturated basal facets and hard refrozen saturated snow. At both study pit locations the extended column propagation tests produced no significant results on the Friday morning ice lens underlying the newest snow, or the soaked remnants of the Halloween crust. All propagation tests required more than 90% of the column to be undercut before failing. The only conclusive result was a stubborn uneven CTE 16 on the soaked remnants of the Halloween crust at the Galatea Meadows study pit, that really just failed as the soaked basal facets fell apart. This is a very dynamic snow pack, there is a lot of thermal energy in this snow pack, particularly in the basal layers, and it will continue to evolve rapidly in an uncertain matter for the near future. These conditions are well outside the range of any of my previous experience so it is difficult to speculate on how the snow pack will evolve under new load. Under these conditions, with this much energy in the snow pack, the presumed persistence of both the Halloween layer and the Friday morning ice lens is far from a forgone conclusion. My ski partners for the day pushed higher above treeline and reported a restoration of the normal early season Rockies snow pack of wind stripped windward slopes, and wind loaded lee slopes, with bullet proof wind slabs. They did not determine what snow the wind slabs were overlying.