Always remember to select your scale before starting a new project. I used centimeters for this one (Fig.01).
We start with two planes. The top one will be the standard ground positioned at Z:0.0, and the second will be just underneath it. Tweaking will be necessary on the second plane; I found Z:-0.4 was good for me. Increase the texture size depending on the scale and level of detail you want. I used 750 by 550, and created a 4K map.
Now created an orthographic camera on top of your scene and make a render to use as a guide in Photoshop.
In Photoshop you should not begin painting with a white canvas, as you will be unable to have negative displacement, so instead pick a colour that will give you enough leeway in both positive displacement and negative displacement. It would be wise to study your scene to figure out what will be needed most.
For this one I used a dark gray since I won't be digging much so: R:77 G:77 B:77 (Fig.02).
Then you just start digging into the snow, removing it where needed. Try to think about how it should look; where are the hotspots that would leave less snow; what kind of shoes a person uses, and how he walks. Obviously try to reduce the amount of snow where there is cover, or where there was cover. You can make a story based around this, eg: a car was parked at one point, but then drove off and left a distinctive mark in the snow.
In some places you will need to add snow. This includes pretty much anywhere where buildup is possible, mostly due to static objects. For example: a wall with the wind against it will harvest more snow at its base.
When you are done, add a noise map overlayed (Fig.03) with the final snow displace. This creates different elevations which supports the fact that snow is never perfectly flat when you examine it up close (Fig.04).
Back into Max we start with two planes. The top one will be the standard ground positioned at Z:0.0 and then make another plane just under it, tweaking where necessary (again, I found Z:-0.4 was good for me).
You do not need to make a dense mesh for this, just a standard plane with four sides. The V-Ray displacement mod will take care of the rest.
I used a Vray shader for the snow, with some blurry reflections and a low Fresnel. I also added a bump speckle for some added detail (Fig.05 - Fig.06).