Depending on how may nights you plan to stay, you'll need lots of things!
A polk sled is key if you plan to cover any ground with any degree of ease. You'll want something with tall sides along the whole length made of thick rugged plastic (In most cases this means a good sled for downhill sledding is not a good polk sled). The department stores are not typically a good source for polk quality sleds. I got mine at fleet farm, but they dont carry that model any longer. Try an outfitter like REI or EMS, and chose wisely.
Depending on your abilities, pulling the sled on Cross Country skis may be more work than it is worth, given the varying terrain in the BWCA. (skiing up hill with a 50-60lb sled tied to your waist aint easy) But, Snowshoes work great on any terrain!
for packing your polk sled youll need at least 1 15'x15' or larger tarp ($5 at any gas station on the north shore.) Depending on how much snow there is you may not be able to dig a fully covered snow shelter and you will need 2-3 of these tarps instead of just 1.
Bungee cords are a must, for packing sleds, making shelters and about 23098423.999 other things, make sure you have several of these.
Rope is VERY useful. Bring AT LEAST 100 feet of braided NYLON rope. useful for packing your sled, making shelters, drying clothes, etc..
Coleman makes a 100' x .25" braided nylon rope i picked up at walmart for $7.99.. a great deal. (Polyester and Cotton rope will become brittle and break in low temperatures)
A small backpack. When pulling a sled there isnt much need to carry everything on your back, but its a good thing to have a backpack handy for daytrips, and easy access to commonly used items you dont want packed away in the sled (e.g. a flask of good Whiskey!!).
A medium sized light weight coal shovel is key for making shelters and digging out the fire pit & latrine. These are available from any hardware store--the ones with the plastic blades are WAY lighter than any metal shovel.
A -15F mummy bag at minimum, -20, -30 preferred--goose down or synthetic, no cotton!! Preferably a bag that comes with a compression sack, for getting the size down when packing the sled. (Kelty makes some good compression sacks for stuffing clothes and sleeping bags also--theyre not exactly cheap but are very well made, i own several)
At least 2-3 pair of medium-heavy polypropylene long johns, (top and bottoms)
This is common sense, but bring a good stocking cap and scarf (wool or poly, NO COTTON!)
Also, bring good weather resistant mittens for when its really cold. I also carry a pair of leather gloves for working around the fire and cutting wood--i actually wear the leather gloves more than anything BUT, dont expect ANY 5 fingered glove to save you from frost bite!! WARM DRY MITTENS WORK BEST!!
several pair of wool socks, and maybe some real light weight silk socks to stop the itch from the wool. Just make sure your boots aren't too tight, or your toes WILL turn black and fall off!.
Good waterproof cold weather boots, preferably with removable liners for easy drying by the fire, (if its extra cold, ill pull out my liners and wear them in my sleeping bag with me.. That way my feet stay extra warm at night, and the liners/boots are warm in the morning, and dry!)
a couple polar fleece or wool hooded sweatshirts, (hooded to keep thewind off your neck)
A heavy winter jacket and snow-pants. These can be really well insulated or just for breaking the wind, but if you get something lightweight, make sure you compensate with more layers of wool/fleece under neath. Spare no expense.
Another good thing to have is sunglasses or ski-goggles. The snow reflects sunlight really well. Use glasses or goggles to avoid snow blindness or a really bad headache.
Chapstick or some other kind of lip balm is important too. Personally I use Dermatone brand lip balm, works great!
Bring a good axe/hatchet and a bow saw.
Firewood will be plentiful, but tinder may not be. You can scrounge for twigs and tinder at your campsite, but its best practice to bring some fire starters with you.
Hexamine or trioxen work great and are easily found at outfitters and army surplus stores.
If you prefer something more "natural" you can make your own firestarters using an old egg carton, some paraffin wax, wood chips and sawdust. Fill the carton's egg slots with the wood chips and sawdust, then pour molten wax over the sawdust, filling all the gaps, then let it cool. (there should be more wood/sawdust than wax). Later when starting a fire, tear one of the egg slots out and use it to get the fire started.
Usually the wood in the winter is covered with snow, so bring something you can fan the fire with also till you really get it roaring.. I carry a small bellows myself, $9 at fleetfarm.
Plan your meals ahead of time and stick to a regiment, dont bring too much or too little. Bring food you can eat without cooking, like nuts, raisins, granola bars and stuff like that... this way you're not forced cook every meal. For the meals you do plan to cook, only bring what you need, a pot, a pan, a spatula, a plate, and utensils. and LOTS of tinfoil--to keep the heat in while cooking.
I found out the hard way that butane stoves dont work too good in sub freezing temperatures. They do work, but not as well as in warmer temps. A white gas stove is the best bet if you don't plan to cook over an open fire.
What else.... Dress in layers, stay dry & dont forget your map!
If you get hot or start to sweat while hiking or cutting wood, take the time to strip off 1 or 2 layers! If you soak your inner layers with moisture from sweat, it will be difficult to dry them out, and youll get cold a lot quicker.
Side note.. So far this year there has been a lot of snow up there an in my experience heavy snow on the lakes can create a layer of slush above the ice but below the snow, Stay on the already blazed trail when crossing lakes in deep snow, otherwise you may end up with boots and a sled caked in thick slushy ice. NOT GOOD!
hmm, wrote more than i expected.. just punch me if im too winded!
And lemme know if this helps