15 to 25 cm of snow fell this week. At lower elevations the snow may be resting on weak surface hoar which could hit the tipping point this weekend, stay alert for changing conditions & watch for stiff wind slabs in exposed terrain which may remain sensitive to human triggering.
A persistent weak layer exists throughout the region 80 to 100 cm below the surface. In most places it looks like the overlying snow is gaining strength and human triggering is trending towards unlikely. However, areas around the Pine Pass may remain problematic.
15 to 25 cm of new snow has fallen in the last week. At lower elevations this snow is resting on surface hoar. We haven't heard much about reactivity with this surface hoar yet, but it could reach the tipping point anytime.
In wind exposed terrain at and above treeline the new snow has been shifted into wind slabs in exposed terrain by ongoing west & southwest wind.
Dribs and drabs of new snow are expected to be accompanied by strong wind throughout the forecast period.
FRIDAY NIGHT: Freezing level around 1200 m, strong west/northwest wind, 2 to 6 cm of snow possible.
SATURDAY: Broken cloud cover at dawn building to overcast by lunch, freezing level beginning at valley bottom rising to about 1200 m, strong west/southwest wind, light snow during the day with 2 to 5 cm expected. 5 to 15 cm possible Saturday night.
SUNDAY: Overcast, freezing level around 1200 m, strong west/northwest wind, 5 to 10 cm of snow expected.
MONDAY: Clear skies at dawn with clouds steadily building to broken by sunset, freezing level beginning at valley bottom potentially rising as high as 1500 m, moderate to strong northwest wind, trace of snow possible.
This week control work produced storm slab avalanches to size 2.5 in steep rocky terrain in the far south of the region. Near McBride, storm slab avalanches to size 2 were observed in north and northwest facing alpine terrain. Losse dry activity in the new snow was also reported.
15 to 25 cm of snow fell this week with plenty of wind from the southwest. This storm snow sits on previously wind-affected snow in exposed areas, soft snow and perhaps surface hoar in sheltered areas, and a hard melt-freeze crust or moist snow below about 1600 m.
You may find a couple weak layers of surface hoar in the top 50 cm of the snowpack, as suggested by numerous MINs in the region. These layers are expected to be found in terrain features sheltered from the wind, for example in openings below treeline or at treeline elevations. As the new snow continues to settle and forms slab properties, these layers could become reactive to human traffic.
Around 60 to 100 cm of snow rests above a weak layer buried in early-December. On Jan 14th our field team found it in the Holmes area. This setup has created a persistent slab avalanche problem and a low probability/high consequence scenario. Depending on location, the buried weak layer is composed of surface hoar and/or a crust/facet combination. Reports suggest that this layer has become dormant in much of the region except for perhaps the Pine Pass area.
