Four Pass Loop
Elk Mountains, CO
Elevation Profile
Current Conditions
Bottom Line
March backpacking is marginal — expect significant snow at altitude with Saturday night's storm bringing 25-30 mph winds and dropping temps to single digits. Stream crossings are normal flows and safe.
36°/9°F · Sunny
Moderate (2/5)
47" depth
Normal flows · 5 gauges
No active fires within 50 miles
11h 50m daylight · Sunrise 7:23 AM · Sunset 7:13 PM
Full Briefing
This is a shoulder season attempt that requires winter gear and experience. The Four Pass Loop sits at 8,000-12,400 feet where Annie Springs SNOTEL shows 35 inches of snow depth even at the relatively low 6,021-foot station. Most of the loop will be under continuous snow cover requiring snowshoes or skis for travel, and many trail markers will be buried. Saturday night's incoming system drops temperatures to 9°F with sustained 25-30 mph winds — conditions that can quickly become life-threatening without proper shelter and insulation. The avalanche bulletin shows Moderate danger across all elevations but with no identified problems, meaning the snowpack is relatively stable after recent settlement.
Stream crossings won't be your concern — flow data from regional gauges shows 38-88% of median flows, well below spring snowmelt levels. The Roaring Fork drainage feeding this area typically runs highest during late May and June snowmelt, so March crossings should be straightforward rock-hopping even if snow bridges haven't formed yet.
The weather window is tight. Friday looks manageable with 34°F highs and moderate west winds, but Saturday brings increasing instability with isolated snow showers developing. Saturday night's system is the real concern — sustained winds of 25-30 mph combined with 9°F temperatures create serious wind chill and hypothermia risk. Sunday maintains cold temperatures and gusty winds with lingering snow showers.
Plan for winter camping conditions throughout. Bring a four-season tent rated for wind loading, sleeping systems rated well below the forecast lows, and navigation tools since trail finding will be challenging in snow. Consider this a winter mountaineering objective rather than traditional backpacking. Start early Friday to maximize your good weather window, and have bailout plans if Saturday's system proves more severe than forecast.
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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