You're on the right track. It's because the range tends north to south, which forms a perfect snow fence. On highways, we use the same thing to keep less snow on the roads. Here's a diagram of how a line of trees forms a snow fence and how the snow drifts on the downwind side:Harlan U wrote: ↑Mon Nov 28, 2022 11:40 pmI think their placement has something to do with the amount of blowing snow that creates isolated areas of extremely deep snowpack in certain cirques.XterraRob wrote: ↑Mon Nov 28, 2022 11:19 pm What area of Colorado had the last remaining significant glacial coverage? I would have thought the San Juans given the average elevation, and amount of rock glaciers around Gilpin, Dallas/West Dallas, and surrounding areas. I seem to remember reading somewhere it was the Front Range around Boulder though.
A mountain range that tends north south acts as a really big snow fence and the same thing happens. More snow actually falls on the west side of the Indian Peaks and RMNP, but since the range works as the perfect snow fence, a good amount is deposited by wind on the east side ridges and cirques. That's why you almost never find cornices in Colorado facing west. They almost always face east (though they can face north or south on occasion).
Even if the San Juans get more snowfall than the IPW or RMNP, it takes much longer to form a glacier than it would if they formed a north to south snow barrier like the Front Range does.
A secondary reason for the glaciers in IPW and RMNP is because east facing slopes are shaded in the afternoon/hottest part of the day, but the most important reason is the "snow fence effect" (my own words for it).