A change was "in the wind" on Saturday at Helen Shoulder and throughout Banff Park. Skied up the Helen Lake Trail to the shoulder. Trail is now super pounded into a luge run. In the morning there was a lot of snow still clinging to the trees with 10 - 15mm surface hoar everywhere treeline and below. Snowpack was still 120 cm and less in general unless you were in a wind deposited lee area. Lots of areas of unsupportive facets and depth hoar made for difficult trail breaking if you were off the beaten paths. Much of the good skiing had been heavily skied in recent days when the hazard was lower. No real cracking, whumpfing or hollow sounds noted until we got to the open ridge crest where the immediate lee had a slab set in which was quickly noticeable as your ski penetration changed radically. Here the surface hoar sat on top of 10cm of low density facets which sat atop a variable thickness stiff slab (25 - 70cm), all of which sits on facets and depth hoar of course.
We did a compression test just in the lee of the ridge crest and got a hard (CTH23) sudden planar "pop" on the facets under the slab. We did an extended column test where the slab was about 60 to 70cm thick and the entire column failed (dropped) and propagated on the 23rd hit again. Even before doing the tests we were getting a bad gut feeling about skiing anything steep, open and potentially lee loaded so we skied a short shot safe then retraced our route.
Some recent avalanches from size 1 - 2 noted on the steep moraines on Crowfoot peak across the valley with the crowns becoming obscured by the blowing wind.
Temperature were moderate throughout the day with a high of -5. Winds picked up from moderate to strong as the day progressed with gusts in the extreme range, knocking people off their feet by the end of the day. Locally the wind was from the NW. It was strong enough to pick snow up from the moraines on Crowfoot and blow it vertically up the face to near the summit! No snow was left on the trees all the way down to the valley bottom.