Bob Foster wrote an answer about CamelBak Fourteener Hydration Pack - 1587cu in on July 22, 2012
Andy, there is a specific deeper pocket in the back of the Fourteener, so I believe your rain gear would fit in there. I'm concerned more about that 300 weight polar fleece, what are the dimensions of the fleece? The change of clothes and hat should be able to fit in the outer stretchable mesh pocket if you wish....gloves will fit in an outer 'bottle' designed mesh pocket or in the small insulated pocket. If you are looking for a more cold weather climate pack then I would recommend a Osprey pack because the water tube for hydration is insulated to prevent freezing.