I observed graupel on top of rain crust on top of older storm snow--noted in the avalanche forecast for 02/24/2021--at and above the talus field which starts at 47.4619, -121.6459 (~4.1k') in morning climb of Mailbox Peak (arrived at summit around 09:15).
The rain crust over the deeper (supposedly 2'+ powder according to prior weekend's WTA trip reports), was very difficult to puncture with microspikes using kicking steps and my La Sportiva TX4s. Partner reported some ease in puncturing rain crust with spike on ice axe, so I assume that crampons would have been required for safe and easy ascent and descent. Gaps were noted in boulder field, so snow coverage was variable/low.
I noticed some small localized carbs falling later on in the morning but nothing serious of note, avalanche risk wise, on the surface. There was a fair amount of wind scouring in sections (mostly south aspects) with loading in leeward areas not along the Mailbox Peak ridge (seemed to be mostly the west side at the base of the talus field).
I didn't dig a pit or do proper handshear tests due to large amount of difficulty puncturing rain crust with trekking pole and microspikes.