The snow above a crust could slide on that crust's upper surface. The crust layer could be an obvious sun crust that is hard or a subtle wind crust you might miss without careful brushing. It is this snow that must have cohesion. If it is a graupel layer it may act like small ball bearings. If it is surface hoar, the little sheet flakes won't adhere to themselves very well.
Surface hoar forms on the surface of the snow at night when it gets colder than the dew point.
It may well get buried by later storms before it melts. If there is liquid water, like in the spring between layers it will lubricate the sheering of the layers. If you go to the trouble of digging a snowpit you should do a snow shovel sheer test. Using a ski like a knife cut a column free from the back wall. You need to cut three sides to make the column free standing.