NEVER, NEVER spray Pam or anything like it on these dishes, whether they are metal or fiberglass - you will eventually buy a new dish as these things will destroy the coating on the dish which reflects the signal off the dish to the LNB...as an installer for more years than I can count, PLEASE don't do that!
Snow & ice will affect the signal (snow moreso as it is less reflective) but a signal strength of 37 sounds pretty low regardless. If, under normal conditions, your signal on 105 is less than say 55, it is not aligned very well and you may want to call dish for a trouble. If it is mounted on the roof, did the installer use the support struts on it? If not, let them know that as well (a Super Dish should never be on the roof without them because of its shape/weight) - may get you a free service call if you'd normally have to pay for improper installation. I can usually peak a 105 dish at about 70 (as high as 81 a few times) but anything above 55 will help the rain fade and snow/ice conditions.