An 18 degree slope is like an upper level "Blue" ski run:
Or a forgiving Black Diamond.
Just for perspective:
A "green" run (easy) at Buttermilk Mountain, Colorado:
slope = .2
20% grade
~ 12 degrees
A "blue" slope (More difficult) at Snowmass, Colorado:
slope = .279
27.9 % grade
~16 degrees
The slope in front of Oppy:
slope = .325
32.5 % grade
18 degrees
A "black diamond" (Most difficult) at Snowmas, Colorado:
slope = .36
36% grade
~ 20 degrees
I didn't bother with the double diamond slopes.
~jms~