Whump there it is

Set out with an assessment mindset given the uncertainty involving wind slabs. We were aiming to ski a few S facing lines on the peak between Fraser and Taiya as we figured the area might be sheltered enough to hold snow. Around 1500m we set off a bone-chilling whumpf that sounded like a bomb going off around us, and propagated cracks over 100m away. Had us both emptying our bibs and thanking jeebus the angle was less than 30 degrees. Slope was south facing and 17° at 1500m, cold and not yet affected by the emerging sun. We dug a pit and did a quick CT in the area and found it took two hits from the shoulder to induce failing on a very hard ice crust around 30cm down. Right on top of that crust was a hard slab around 10cm thick, with 20cm of soft snow on top. The rest of the snowpack was one finger to four finger hard facets all the way to the base. We were surprised by the size, propagation, and aspect of the signal as we weren't expecting any signs of instabilities on S facing slopes. Turned around and called it a day after that. Otherwise beauty day in the hills.