Generally around 120cm (50") in the upper Mill Creek area with a 4finger to 1finger slab on top of well developed weak sugary faceted snow. Locations like Mill Creek where the snow pack is somewhat shallow I would think it is more likely that a person could trigger an avalanche by impacting the weak snow near the ground.
Lots of wind affected snow in upper Mill Creek and a fairly recent natural avalanche that broke about mid slope where the snow might be a little shallow and was quickly over loaded by dense wind drifted snow. Other avalanche paths looked like there had been some large slides where the debris was quite deep when the avalanche stopped.
Fresh wind drifts on the leeward side of the ridge lines were a little sensitive and would break up to a foot and a half deep, these could get more connected with continued winds.
