is there a certain 16mm film stock i should use when shooting in the snow? im using my k-3 for a snowboard vid.

There are people a lot more knowledgeable than me in filmstock related questions, but I would suggest you keep in mind how bright it is likely to become. You could go with a low ASA rating, like 50, or you could get an ND filter, or polarizing filter, which might be better, because that would add some protection between your lens and all the show and water drops and such. You'll definitely want to do something, or else you'll be getting tons of ƒ22+s and not be able to do anyting about it.

I'm back from vacation.

The best stock depends totally on the lighting conditions. The presence of snow does not really affect this, except you will generally need to overexpose compared to the reading from many reflective meters if you want detail on faces and darker objects. Incident meters are easier for these situations.

What time of day are you shooting? A decent choice for full daylight is 50ASA or 64ASA (Fuji). For lower light, 250D is a good option.