Teravail Cannonball 650b x 40
From the description- Its center tread is tightly-knit, meaning that you have less rolling resistance, while the diamond pattern takes on gravel to give you the most grip possible, shredding and shedding dirty terrain.
This may not be a real good tire on snow. My opinion- you need something with an open spaced out knobbie pattern, all the way accross the width of the tire. If the center gets filled in to make it roll better on hardpack or such, it's not going to ride like a real knobbie tire. I understand your constraint with 42mm limits your choices, and I have never ridden a Teravail Cannonball or a 650B bike. I commuted for years in the winter with 26" hard tail / fork mtn bike and 1.95 or 2.2 soft compound knobbie tires at reduced pressure in NoDak.