north twin conditions
Addendum to my earlier post: Not only are most road maps wrong, most maps also show the trail in the wrong position. (The AMC White Mountain Guide has it right, though.) [The location of the crucial third river crossing, and the trail's direction after making it, are wrong on all other maps I've seen: the trail continues due south (and fairly flat) for a while after the crossing, whereas most maps show it turning dramatically west and climbing sharply.]
Here is one of the few road maps that's accurate.
As you can see, Little River Road (which is plowed) will get you to within about a mile of the trailhead at the end of Haystack Rd. Follow Little River Rd to the gate with the No Trespassing signs, park there and cross the wooden bridge (snowmobile trail) a few feet away to the west. Immediately (as in as soon as your feet leave the bridge) turn left (south) onto an old railroad grade (there will probably be ski tracks, but no snowmobiles due to some very minor downed trees). Follow this straight south, parallel to the river, til you hit Haystack Rd at the trailhead.
The trail is very well marked and blazed, just follow it and you'll have no problems. (Ignore your trail map!) We barebooted yesterday (even off-trail), but obviously fresh snow might mean you'll need snowshoes. The three stream crossings are easy to spot and easy to make (the river is frozen solid at all three). The bushwhack that avoids the first two crossings will probably be packed down more than the trail itself, but either way will work fine. I recommend staying on the trail to avoid all risk of following the wrong tracks (eg, mine when we did some silly bushwhacks for the fun of it).
This isn't posted under trip reports because we turned around before getting very high on the mountain (we let our maps convince us we were on the wrong trail, and doubled back for a lot of fruitless searching), so I can't say whether, for example, crampons might be needed on the steepest sections.
