This winter I did a good chunk of biking thru the snow... My suggestion is wool glomitts. They're wool half-finger gloves with a 'mitten' part that folds back over the back of your hand... and they're lined with polar fleece. I'm not sure if that'll help you, but if you wear your 'all season' gloves under them, your palms should stay warm enough to maintain heat in your fingers.

What I'd be more concerned about is how warm you're keeping your core and head. With adequate insulation in those areas, your extremeties (sp) should (yes, "should" doesn't always translate into real life) stay warm enough. Trek should have some ideas... she's from roughly the same area I'm originally from...