To weight or not to weight......that is the question.
Weighting is not normally required providing the tires can find enough traction to control the direction of the tractor. However, if you have the blade at full angle and you are trying to move a monster sized windrow over another six inches, then more weight on the front end probably won't make a bit of difference. That's when you change your ploughing methods by making the blade straight and then pushing the windrow from a 90 degree angle to move the bulk of it off the area you are cleaning. Then you can angle the blade once again for the final cleanup.
Whether you are ploughing snow or blowing snow, it is a learning experience every time you go out because the conditions are always changing. One time the snow may be very dry and the next time it is super wet. In addition, the conditions can change rather rapidly while you are clearing the snow. Putting an aggressive tread pattern on the front rims is your starting point. Only then should you worry about adding weight if traction is still a problem.