Observation: NWAC Observer

All Observations

Basic Information

Observation Details

Observation Date:
December 19, 2021
Submitted:
December 19, 2021
Observer:
NWAC Observer - Drew Lovell
Zone or Region:
East North
Location:
Hwy 20 (E thru S, 3000'- 6500')

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced

Media/Attachments

HS 155cm. Right side up hardness profile. Early Dec crust down 120cm. Delancey Ridge, 6100ft, S
Widespread cycle of storm slab avalanches mid to late storm on Dec 18th. Washington Pass. 6,200ft, S

Advanced Information

Weather Summary

Cloud Cover:
Clear
Temperature:
10°F
Wind:
Calm , SW
New/Recent Snowfall:
HST 45 cm, fairly consistent from valley bottom to ridgecrest. Blower.

Clear cold and beautiful, with the huge moon setting with the sunrise. No wind transport, although the entire pack is basically available for transport, if the wind should choose to blow.

Numerous sz.1 - 1.5 storm slabs observed, mainly on steep features between 5000'-6500'. We estimate that they ran in association with warming and precip. intensity, mid- to late storm. Debris was fairly soft, with 15-20cm overtop, making for decent skiing. Crown depths were approx. 30cm and partially filled-in. A few steep, sustained gully features ran perhaps 1000' vertical, but most debris stopped within 500' of the crowns.
The most significant pertinent negative was the lack of evidence for smaller storm slabs stepping down and initiating larger avalanches at the Early December Crust interface. The avalanche cycle was certainly widespread and thorough, and seemed to occur in a fairly narrow time of peak instability.

Snowpack Observations

HS on Delancey was probed at 110cm near valley bottom, and ranged up to 160cm near ridgecrest.
HST consisted of 45cm F hard blower. This gradually trends favorably to a 1F hard lower pack.
Any instabilities in the recent storm snow have subsided, and tests at the new / old interface could generate resistant and unremarkable results. No wind slab observed today.

A test pit @ 4600' on a SE aspect held an HS of 110cm. The Early Dec. Crust was absent and tests were unremarkable.

Another test pit @ 6100' on a S aspect held an HS of 155cm. The early Dec. Crust was present and down 120cm. No noteworthy results within the upper or mid pack. Compression and Deep Tap tests yielded Hard, Sudden results on rounding faceted grains that overlie the Early Dec. Crust.

A weak sun crust formed today on very steep due solar features.

Avalanche Problems

No problems observed today other than very low-density dry loose with minimal entrainment.
Nonetheless, we remain cognizant of the faceted grains that overlie the Early December Crust, where it exists in the local mountains. It is worth probing for the crust as one approaches 5500'-6000', and, if found, acknowledging that one is entering a more-complex snowpack environment.

WordPress Lightbox