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Ptarmigan Glacier

40.3125, −105.6996 · 3,587 m · NNE · 23° · 0.6 ha on Sep 22

Snow · small

From the satellite, Sep 22 pass. No ground report in the last 10 days.

What the satellite saw

Drag the handle to compare two passes; tap a pass below to change them. The blue line is what the scanner counted as snow.

0    200 m
N
Every pass this season · tap one to compare it

Sentinel-2 L2A true color, read at 20 m. One pixel is 0.04 ha. A strip narrower than about 40 m can hold skiable snow and show nothing. By mid-September, north-facing cirques sit in shadow at the late-morning overpass, so one zero isn't proof of anything.

Reviewer notes

  • Sep 27 pass · excluded: in shadow

    In shadow, exclude this pass

    Patrick · Sep 28

An admin checked the imagery. An excluded reading stays visible above but doesn't count toward the status.

Getting there

Approach
~3.5 h · 6 km one way
Route
Bear Lake TH, via Flattop Mountain trail; the glacier sits just north of the summit plateau
Approach from
Munter rule from straight-line distance and climb, from the first analysis. Rough.
Route from
Unverified: written during the first analysis, not by someone who went.
Terrain from
From the first analysis: a coarse elevation model at one point. Not checked.
Open Sep 22 in Copernicus Browser Open in CalTopo Download snow outline (GeoJSON)

From the ground

No reports for this snowfield yet. Members post what they find on the ground.

Snow on each pass

Hectares of counted snow per pass, as a chart. Grey stubs are passes with cloud over the snowfield.
0 ha12345JUL 4: cloud or not coveredJUL 9: cloud or not coveredJUL 14: 4.9 haJUL 19: cloud or not coveredJUL 24: 1.9 hashadow?JUL 26: 3.2 haJUL 29: 2.9 haAUG 3: 2.3 haAUG 8: cloud or not coveredAUG 13: cloud or not coveredAUG 15: cloud or not coveredAUG 18: cloud or not coveredAUG 23: cloud or not coveredAUG 28: 0.04 haSEP 2: 0 hashadow?SEP 4: 0.4 haSEP 7: cloud or not coveredSEP 12: cloud or not coveredSEP 17: cloud or not coveredSEP 22: 0.6 haSEP 24: cloud or not coveredSEP 27: 0 ha, excluded by a reviewer (in shadow)excludedOCT 7: cloud or not coveredJUL 4JUL 24AUG 8AUG 23SEP 7SEP 24OCT 7

How we got to this status

  1. A reviewer excluded this snowfield's reading on Sep 27 (in shadow) after checking the imagery. The status comes from the other passes, the latest being Sep 22.
  2. The Oct 7 pass was cloudy over the snowfield (86%), so a cloudy pass counts as no look, not as zero. This uses the Sep 22 pass.
  3. Sep 22 pass fully covers the snowfield and is clear over it.
  4. 15 snow pixels in 2 clusters, which is 0.6 ha.
  5. Not flagged as possible new snow.
  6. Under 1.0 ha, so it's marked Small.
Scan run 7 · status rules 2026.09-2
NDSI > 0.4 · NIR ≥ 0.6 × green · SCL mask · algorithm 2026.09-2
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