What effect would a ND filter have on snow shooting?Reason I'm asking is because yesterday when I left the house it was overcast but when I got to my destination the sun broke out and I was forced to shoot wide open.
It will, of course, will reduce your stop. An ND filter would cause you to need to shoot a larger aperture, or slower shutter speed. If you had to shoot wide open with the sun out, an ND would force even slower shutter speeds. The statement "Reason I'm asking is because yesterday when I left the house it was overcast but when I got to my destination the sun broke out and I was forced to shoot wide open." is kind of an oxymoron, I assume you meant to say "stopped all the way down"
Since a standard ND filter affects all exposure range in an equal way, it would have no different effect on a snow scene than it would on any other kind of scene, affecting only overall exposure, with all values remaining relative. However, a graduated ND could be a useful tool for snow scenes in some compositions.
Regarding the OP, my standard practice would be to use a spot meter to determine individual values. If I
had to use an incident meter, I would use the meter to obtain a reading consistent with the light on the subject of interest, meaning I would use the meter differently for a person (metering for the light on the face) than a landscape (metering in a bright area and a shadow area, and determining my exposure by those readings, the conditions, and overall composition considering how much detail I wish in the highlights, or low values. If the scene exceeds the range of the stock, you gotta choose what you want to keep and what you let go, on one end or the other.)