Travel was above Snake Creek and the head of American Fork Canyon. Mostly, we saw avalanches breaking in a density change in the new snow; HOWEVER, we also triggered an avalanche on small facets just above an ice crust. This concerns us, as this type of instability can last much longer. This weak layer was capped by 2-4" of snow on Valentine's Day. We suspect it will only be a problem where it rests on top of an ice crust, which could be on west, east, and south aspects. Another layer, which hasn't been an issue, is just under the early February snow. We'll keep looking for these layers to see how widespread they are and how long they last. For now, it's worth digging about 3 feet deep and testing these layers. A bad test result is all you need to change plans. A good test result means you should keep looking.”