Best winter sleeping bag for the Adirondacks?

It can get really cold in the Adirondack mountains during the winter. Temperatures can regularly dip into the negative (without windchill). During the months of January and February, the average low temperature is typically around 0 degrees Fahrenheit, but temperatures have gotten as low as -30 (without windchill). The average temps will be in the teens or single digits, but with winchill it can feel much, much colder. So essentially, you'll want a sleeping bag that can get you through some very cold winter nights. If you are going to be sleeping in a lean-to, you'll want to also use a bivy sack such as the Outdoor Research Alpine Bivy. A bivy sack will keep you 15 degrees warmer, as well as protected from wind and blowing snow.

To deal with the cold temps, an Adirondack winter sleeping bags should be rated to at least -20F (-28C), but you may really need a -40F degree bag. Here are some -20°F winter sleeping bags that you might consider: 

• Mountain Hardwear Wraith -20°F Degree Down Sleeping Bag
• Western Mountaineering Puma Gore WS -25 Degree Down Sleeping Bag
• REI Expedition -20 Degree Down Sleeping Bag
• Marmot Col MemBrain -20 Degree Sleeping Bag
• Feathered Friends Ptarmigan EX -25 Degree Down Sleeping Bag

However, if you sleep cold, you should definitely consider a -40 degree bag, because depending on the weather, temperatures can get extremely cold especially in January and February in the Adirondacks.

• Marmot CWM Membrain -40 Degree Sleeping Bag
• Feathered Friends Snow Goose EX -40 Degree Sleeping Bag
• Western Mountaineering Bison GWS -40 Degree Sleeping Bag
• Mountain Hardwear Ghost -40 Degree Sleeping Bag
• First Ascent Karakoram -30° Sleeping Bag

You can use a synthetic fill sleeping bag that's rated to at least -20 degrees, however they are often 20% to 40% times heavier for the same insulating value as a Down fill sleeping bag.  On the plus side, synthetic sleeping bags will retain a substantial portion of their loft and continue to provide insulation even when damp or wet.