Marmot Ion Wind Hoodie
Right now there is a coupon for 35% off, making it $31.82. My large weighs 145g/5.1oz.
However, (and this is a little too late for me) there are some bad reviews on here for it, saying it doesn't breathe well. My experience so far is that it's not too bad. There is mesh under the arms and behind the neck...I wonder if these were added on after hearing some reviews about it's breathability. Not sure.
As for the Boreas, I figure it would be a lot more breathable and functional than the Marmot Ion. I'm taking a trip to Colorado this summer, and the last time I was there I was shocked at how many times I had to go from teeshirt to synthetic jacket. When the sun would hide behind the clouds, it felt like it dropped 20 degrees. Not having a mid layer that I could use in both sun and shade (like a Boreas) was really frustrating. Here in the southeast, we have this thing called humidity, which tends to normalize temps between sun and shade ;)