Are you going to backpack or use a dogteam, mechanical vehicle or just how will you travel? NO blanket, skin robe or other contraption OR cheap POS bag from Coleman will consistently work in real cold like a top end down bag, properly used.

IF, you are going to backpack in cold weather in Alaska, you cannot carry everything you require plus all the heavy extras suggested here and this IS a BACKPACKING forum. Do not be led astray by what "might" work or comments about situations much different from the reality of backpacking in cold weather, buy and use one of the bags I told you about and you will enjoy your trip.

A GOOD -25F bag, like the ID-XPDII, WM Puma or Valandre SB or Odin is by far the most efficient way to go and, with care, such a bag is a lifetime investment. The weight will be between 4-4.5 lbs. plus VBL, maybe an eVent bivy at 1.25 lbs and your pad(s) at roughly 3-3.5 lbs. all in. This WILL WORK and better than any other option; a synthetic bag that is warm enough is too heavy and bulky to backpack...and I have 3 now and have had several others.

My work and hunting bag(s) is the ID North Twin/Andromeda Overbag Primaloft synthetic combo, good to about -10F, but, it weighs 5.25 lbs. and is NOT as warm as my 3lb. Valandre Shocking Blue down bag....THIS is the bag you SHOULD buy.