I picked this one that I had started last year (see post on 08 October 2012) and lightly sketched in where I wanted to lift a few more snow covered trees from the background.
Using water I lifted out more snow covered tree shapes from the background, removing more of the paint from the closer ones and less from the more distant ones.

With a dark green mix of French ultramarine blue and raw sienna I added a few more needles to some of the snow covered foreground trees.
The painting needed some deciduous trees into the background so I lightly sketched then in with a pencil.
With a grey made of French ultramarine blue and burnt sienna I put the darker trees into the foreground and gradually added more water to the paint mixture to lighten the colour as I painted the trees that were further back in the painting.

The OSWOA shown here is an original watercolour painting using Artist quality Winsor & Newton paint on 300lb. Arches 100% rag, acid free watercolour paper. It is priced at $40.00 and sold unframed.
If you would like more information about OSWOA please go to my post on 12 March 2010.