During the last 4 days especially, we have had large diurnal swings in SWE.  I can understand snow melting off in the morning, even now melting completely to get to a SWE of 0cm, but I can't understand a build up at night again to previous values, especially since the last 3 days have been completely clear days (and presumably nights) with no snow.  This appears to me to be a temperature artifact – it is getting pretty cold (almost down to -20 C) at night, though the snow pillows are supposed to apply a temperature correction, I thought.