Beautiful images. Your system must be working. When I take pictures of this type I put the camera in face recognition mode and the camera is smart enough to read the light only from the recognized face and nothing else. This works if the background is a black tunnel or brilliant snow. But you are right, one should a bit overexpose because snow pictures should be generally whiter than others, even the face itself. The most important thing is NOT to leave the camera on matrix metering mode which will average the image and expose for grey.
Some more if anyone needs this:
The camera would always expose the selected area (spot, scene, whatever) to (18% grey + minimum highlights and no shadows)
So if your image is mostly white, use + EV values.
If your image is mostly black, you may need to use - EV to prevent overexposing blacks. :)
Canon users, turn HTP on all the time to ensure better details in highlights and to get a better dynamic range.
55-250mm standard lenses. Dual tube macro flash and external speedlit...