Is it the tires or the car???

As I sit in my little bungalow on the second day of heavy rain....I start to think about preparing for the winter with the proper vehicle!! Last night as I was driving home my car was sort of slip sliding in the rain!! Now granted my tires are worn.... I have made numerous trips back and forth to San Diego in addition to driving another 10,000 going back and forth to work from Dayton to Truckee this summer!! Needless to say - My Rogue is a good little car and I love it!! But I want to feel safe driving in wet & snowy conditions. So the question is this.... Do I need to trade out my Rogue S for a Rogue AWD or can I just put on a real good set of snow tires and still be Safe!? My driving in Truckee is limited to in town and over to Tahoe City for work. Typically about 15 miles on hwy. 89 (fairly flat). I don't see myself driving over any passes during a storm and from what I hear the area is plowed pretty quickly after snow!! Im looking forward to hearing from all you professional snowy road drivers!!