Weak Layer

Comments:

Name: January 30 facets or late January facet-crust sandwich

Author: DG

Zones: STV, EN, EC, SNQ, WS

Comments:

20220131: DG; This layer is often made up of two layers combined. The 1/20 MFcr was buried by snowfall that then faceted. These FC were then buried on 1/30. This layer has been widely observed in the STV and SNQ areas.

MP reported a thin ZR crust capping the facets below the inversion line at STV. Near SNQ and Crystal, a temperature crust often capped the FC on NW-NE aspects. Occasionally large SH was seen at this interface but seems to be much more localized than the FC and FC/MFcr combos.

20220201: MP; Added SH as secondary grain type after multiple parties observed it in failure layer (MP/Julz Holder) DG, MP, and AH observed facet/crust sandwiches as described above in STV, SNQ, and Crystal respectively. MP and separate public parties observed whumphing and long shooting cracks in Henry Crk Clearcuts 4-4.3k on NW-NE aspects mainly where wind drifting left ~50cm over the layer, HST at 30-40cm at the time in the area. On 1/31 Julz Holder (Avy Instructor) noted touchy conditions at similar elevations with long shooting cracks, and large SH encased in 1/30 freezing rain down 50cm on NW at 4,200ft Yodelin.

20220204:DG: Rainier,TatooshRange.FC/MFcr generally down about 30-35cm in wind sheltered areas. At the surface in some wind stripped spots. 2-10cm of 1-1.5mm FC between crusts. Distribution is limited in this area due to wind effects above 6000′. Most likely in the NTL band only.

20220205: JH Very active day with a handful of natural and triggered persistent slabs to D2.5 in WN and EN. SS-ASr-R4-D1.5-O from 200m away near Harts Pass, sympathetically triggered another SS-D1. SS-ASu-D2-O Maple pass w 3ppl involved, partial burials, no injuries.

20220207: MP: Incredibly reactive conditions with widespread localized collapsing underneath crust with human weight. EN-Powdercache zone. Observed large, flattened SH directly over smooth, brittle IFrc from 3,200-4,800ft on N’ly aspects. Faceted percolation tubes apparent in some areas between crust/facet/crust layers in mid 5,000ft zone. Large whumphs beneath upper crust underneath stiff windslab above 6.6k. Reports of rolling collapses continue to come in from NCH/NCMG in their tenure (2/8).

20220211: JH PS dropped from STV after warming trend, minimal signs of instability in the past week from this zone. Tests showing strengthening. still some indicating propagation, tho variable. No known avalanches on the pwl in the zone.

20220211: JH, EN- Gaining confidence on solars w stout surf crusts and signs of rounding, even MF, at late Jan FC. Still producing collapses near Harts Pass and remains possible on polars in much of zone. SS-N-D1.5-O Porcupine pk. Other Naturals in WN on Table Mtn and Shuksan.

20220225: JH EN- PS unlikely, W-N-W, NTL, ATL. Last known avalanche was on 2/11. Collapsing dramatically decreased in late Feb. Test results becoming less consistent w some ECTN/X, tho CT often produces sudden results.

20220303: JH EN- 2/26-3/1 storm likely re-activated late Jan FC w dry avy cycles on 2/27-28, and wetter avalanches on 3/1.  Not tons of evidence, but a couple of deep crowns on unsupported NE in the Hairpin valley, a couple deep crowns near Azurite Pass, and a very wide slide triggered 3/3, SS-AMu-R3-D3-O, NE, 6,700, Tatie Pk, Harts Pass area.

20220309: JH EN, WN, EC- Jan FC at a wide range of depth around Hwy 20 70-200cm. DPS becoming isolated and stubborn, tho still active. SS-ASr-R3-D2-O, N, 6,600ft, Allen Basin near Harts Pass, 3/9. Evidence that the weak layer could still produce avalanches outside of Harts Pass and ENorth zone from recent obs on Ruby Mtn (WNorth) and MP avy ob on McGregor (crown 2mx80m on NNE, 7100ft) in ECentral.