Merino wool undershirt, medium weight mid layer, and a UA hoodie will get me up there without killing me with heat.
But, you freeze your ass off once you are there. A stout puff that'll pack in a gallon ziplock is what you want for cutting wind, and keep you warm in the coldest wind with damp underlayers. Not good for hiking in, but it'll be worth it's weight in gold once you get there.
Good luck.
