Observation: NWAC Forecaster

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Basic Information

Observation Details

Observation Date:
December 3, 2022
Submitted:
December 3, 2022
Observer:
NWAC Forecaster - Josh Hirshberg
Zone or Region:
East North
Location:
Hairpin, Early Winters creek (5,100-7,600ft, W-SW)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
Isolated

Media/Attachments

Weak dry snow still exists near the surface. You can see 2 interfaces failing in this test.
Pointing out a the mid November facets under a crust in the lower half of the snowpack. Height of snow 100cm. Hairpin Valley, WSW, 6250ft
Very shallow 2-3" chunks of wind slabs could be initiated on kickturns above treeline. Hairpin valley, SW, 7,500ft.
The Liberty Bell group poking out of valley fog and temperature inversions.
The ridge of Copper benchmark and Pica/Poster peak rise above valley fog and teperature inversions.
Debris and crowns, in red, from a couple of small slab avalanches that occurred around 11/30. WNW, 7,400ft
The blue card is at the interface of the mid November facets and a weak crust. Found sudden test results at this interface. Height of snow 100cm. SW, 6540ft, Hairpin Valley
A party of 3 initiated a large whumphing collapse in this area that propagated at least 30 feet. The red lines highlight cracks that connected areas of shallower snow around rock features. 7600ft, SW.

Advanced Information

Weather Summary

Wind:
Calm
New/Recent Snowfall:
HN24 1-2cm

Very calm quiet day with great visibility. No wind xport, had to search hard for the slightest puff of wind. Temperature inversions and a bit of moisture in the atmosphere were the only notable weather factors. Temps stayed cold in the valley all day. Near and above treeline warmed significantly relative to the valleys and received quite a bit of sun for the time of year.
Dynamic cloud cover- Valley fog to 6500 in AM, dropping to valley bottom around 11a. By 12p a thick band of "upper level" clouds capped most ridges for about an hour. Finally all clouds cleared for blue-bird conditions till sunset.

A few small, older, natural slab avalanches from roughly 11/30 above treeline. D1 x3. WNW, 7,400ft. See photo

Snowpack Observations

Signs of instability:
- A large collapse, propagating 10m, in an area of patchy, older wind-drifted slabs (~10 days old) sitting on 1.0mm mid-November facets, roughly 30cm above the ground. Snowpack was 90cm deep and void of any crusts. 7,600, SW. See photo
- Cracks shooting through very thin, 5cm, recent wind slabs 7,500ft and above on SW. Any resulting avalanche, may not have been big enough to knock a person off their feet.
-Predictable, but terrifying whumphing collapses, propagating 20m in the valley bottom. One smaller collapse was @ 5400ft, W.
-Sudden test results on the mid-November facets in the lower half of the snowpack. 6540ft, WSW.

Height of snow:
7600ft- 70-130cm
6,500ft- 100cm
5,100ft- 65cm

Profile- 6540ft, SW
HS 100cm
55-53cm crust, Nov 25
@ 53cm CTM (RP), CTH(RP), variable resistant results
46-40cm P+ hard, crust, Nov 22nd
@ 40cm, 4F hard, 1mm, "mid-November" facets, CTH 21, 26 (SP), variable sudden results

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