I have been receiving this question a fair bit. Having only been open two seasons, we don't have the history we do on other trails, but we think a 35-40 inches deep base is a good number for an approximate Montezuma Bowl opening. Of course there are lots of variables that impact this and they change from year to year. I do have some good news on Zuma. Opening the top requires a fair bit snow farming and snow cat operations. The cat crew had a great start back there and we have corduroy surfaces down Columbine and Larkspur all the way to the Tower 13 zone. Every time the wind blows, it snows a bit, and we catch the snow behind our snowfences, the cat drivers will push the trail down a little further. Those wooden, 8 foot tall fences you see back there are critical in the snow farming program.
Of interest on another note, Pali trail is usually opened with 30-35 inch base. Very early this season, Pali had a large avalanche that buried the willows and brush on the bottom. I don't think it will take a whole lot of snow and wind to fill in the top. I suspect that trail will open relatively soon with very good cover down low from the avalanche debris. If you have been up here, you have noticed the extensive work (explosives, foot packing, ski packing, boot packing, etc.) the ski patrol is doing on Pali. Kudos to them. Think snow.