FWIW.....I don't think snow insulation is a factor, in my experience the cold start problem is totally random except for the cold ambient temps being a constant and even then not always......
I am beginning to zero in more on oil since in my case vacuum leaks have now been eliminated, I have always run with Castrol 0W30 and switched this year to 0W40 and I think my starting issues have gone worse and more frequent thus far this winter, also my mileage has gone south to the tune of 10%. Am going to experiment with an oil catch setup preventing the CCV from putting oil in the intake, there is another thread where I picked this up from. Haven't installed it yet but got all the needed parts.

Tried to attach a pic but lately this site won't accept png pics from my iPad will do later from my pc but here is the link, this is on a N62TU engine but you get the idea. Just have to cap off that lower drain not shown here.

Bimmerfest - BMW Forums - A B Able Truck's Album: Oil Consumption (CCV) fix - Picture

Btw. It's -4C out here today and will hook up INPA Before starting car today and take the valvelift reading. Keep you posted.

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E39 528i 1998, 5 spd black, 350Kkms and going..with new owner.
E60 545i 2004, 6 spd steptr. mystic blue, Tom Sellick's old car, Adaptive steering, Adaptive Xenons, Anti dazzle mirrors and FAST!!!, BT&Aux+SB Chime+Dig speedo+iDrive discl. Coded