Had wet weather problems with a sensor 2 years ago. Once it dried out the problem went away.
Without either Yokohama Ice Guard or Bridgestone Blizzak Winterbiter, my 1999 Subaru Outback did poorly in snow and ice here in the Colorado Rockies. But once I installed the Blizzak or Yokohama clones of Blizzak tires, the car did fantastic in snow and ice. In fact unless the snow is 8 inches or more deep my Blizzak equipped Outback is better in snow than my 4WD Jeep Cherokee.
I would liked to have had more info about your Subaru.
As far as tires go, an excellent all season tire that actually does well in snow is the BF Goodrich Traction T/A.
After much research, I put a set on my VW and thus far are doing great even in the snowy/icey conditions we experience in New England. I wouldn't say it's equal to the 4WD traction of my Jeep, but I wouldn't hesistate to drive on them even in a snow storm.
I have had great luck with Nokian Hakkapeliitta's both model 10 and Q. They are Finnish tires and wonderful in here in the UP of Michigan where we get over 200 inches of snow annually. A bit hard to find and priced the same as other winter tires, but I feel they are worth every penny….the Finns really know how to make things!!!