Four Pass Loop
Elk Mountains, CO
Elevation Profile
Current Conditions
Bottom Line
Stream crossing data looks mismatched — the gauges returned are all California stations (Salinas, Alameda, Llagas Creek), not the Maroon Creek/Snowmass Creek drainages on the Four Pass Loop. Treat stream crossing risk as UNKNOWN, not confirmed. Weather data is also unavailable. Avalanche danger is Low with no identified problems — snowpack isn't the concern here. Get current NWS and USGS data for the Aspen/Maroon Bells area before you leave.
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Low (1/5)
56" depth
High flows · 5 gauges
No active fires within 50 miles
13h 6m daylight · Sunrise 6:36 AM · Sunset 7:42 PM
Full Briefing
The biggest caveat on this briefing: the stream flow data returned is from California watersheds, not the Elk Range. Those gauges (Salinas River near Bradley, Llagas Creek near Gilroy, Alameda Creek at Sunol) have nothing to do with Maroon Creek, Snowmass Creek, or the drainages you'll be crossing on the Four Pass Loop. Disregard those numbers entirely. The real question for mid-April on the Four Pass is snowmelt-driven flow in Snowmass Creek and the creek crossings near Fravert Basin — and without valid local gauge data, that's an open variable. April is historically when these crossings go from manageable to legitimately dangerous as daytime highs push snowmelt hard. You need current USGS data for Maroon Creek near Aspen (USGS site 09073400) and Snowmass Creek before you commit to this route.
Avalanche is a non-issue. CAIC is calling Low (1/5) at all elevations with zero identified problems. The Four Pass Loop crosses above treeline on all four passes — Buckskin, West Maroon, Frigid Air, and Trail Rider — but with Low danger and no active problems, you can move through that terrain without special concern. The snowpack is still substantial (the Long Lake SNOTEL at comparable high-elevation terrain shows 102 inches depth, though that station metadata looks off — the elevation listed is 840 ft which doesn't match a mountain snowpack, so treat that depth figure as approximate). Expect significant snow on north-facing slopes and at the passes themselves. Travel will be slower and routefinding may require attention above treeline.
Weather data is unavailable through NWS, which is the other significant gap. April in the Elk Range means afternoon thunderstorm potential is real, especially by mid-month. Without a forecast, you're going in partially blind. Pull the Aspen/Pitkin County NWS forecast before departure and check again the morning of Day 2. Standard protocol applies given the uncertainty: be below or off the exposed pass crossings by noon each day. With 13+ hours of daylight you have plenty of room to start early.
No fires within 50 miles, air quality is a non-issue. Plan your crossing schedule knowing that snowmelt flows peak in early-to-mid afternoon on warm days — cross Snowmass Creek and any other significant drainages in the morning. If you can't get valid local stream gauge data before you leave, build a conservative turnaround plan for any crossing that looks sketchy.
Waypoints
Maroon Lake
Start at Maroon Lake with views of the Maroon Bells. Take the bus from Aspen.
9,600 ft
West Maroon Pass
First pass at 12,500 ft. Views of Maroon Peak and Pyramid Peak.
12,300 ft
Frigid Air Pass
Second and highest pass. Steep approach from the Fravert Basin side.
12,500 ft
Trail Rider Pass
Third pass. Snowmass Lake visible from the descent.
12,201 ft
Buckskin Pass
Final pass with sweeping views back to the Maroon Bells.
12,300 ft
Return to Maroon Lake
Complete the loop back at Maroon Lake.
9,600 ft
Route Details
Distance
27.0 mi
Elevation Gain
10,000 ft
Elevation Loss
10,000 ft
Max Elevation
12,500 ft
Estimated Days
3
Trailhead
Maroon Lake Trailhead
Best Season
July through September. Snow on passes possible into July.
About This Route
The Four Pass Loop near Aspen, Colorado is one of the most popular backpacking routes in the state, circumnavigating the Maroon Bells-Snowmass Wilderness over four passes above 12,000 feet. The 27-mile loop can be completed in 2-4 days and offers non-stop alpine scenery. The route crosses West Maroon Pass, Frigid Air Pass, Trail Rider Pass, and Buckskin Pass, with each pass delivering panoramic views of the Elk Mountains. Between passes, the trail descends into wildflower-filled valleys with reliable water from snowmelt streams. The Maroon Bells themselves—perhaps Colorado's most iconic peaks—are visible from multiple points. The loop is best done counterclockwise, starting from Maroon Lake. Camping is available at designated sites in some valleys. The area sees heavy use in July and August. Bear canisters are required. Afternoon thunderstorms are almost guaranteed, so plan to be below treeline by noon.
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