Heap of snow

Dirty big heap of snow. Or is it 'big heap of dirty snow'? Or even big dirty heap of snow?

Couldn't sleep in the night and wandered into the living room where I could see (well hear mainly because I didn't have my glasses on and all I could really see were the flashing orange hazard lights) the contracted snow plough clearing the car park opposite the flat. This is the resulting heap.

I'm nervous because the last time it got warmer and the streets and pavements got clearer, that was in preparation for Monday's unforecasted big dump. Has the thaw finally started for real?