The warm temperatures are a good thing for our snowpack long term, but warm temps Friday night into Saturday may allow for human triggerable avalanches Saturday, especially in more extreme terrain. Cornices are expected to remain fragile Saturday too.
Once it gets cold again these wind slabs are expected to be neutralized, but warmer temperatures Friday night into Saturday may allow for some human triggerable wind slab avalanches yet, especially in extreme terrain.
Weak snow at the bottom of the snowpack hasn't gone away unfortunately. Cornice failures become more likely during these kinds of conditions and a failing cornice could be the perfect trigger for the deep persistent slab. Human triggering would be most likley around steep rocky terrain features, or anywhere the snowpack is thin and weak.
Warmer funky weather is with us for the forecast period.
FRIDAY NIGHT: Freezing level around 2200 m in the early evening lowering to about 1500 m by dawn, moderate to strong west/southwest wind, 2 to 6 mm of rain expected at lower elevations, wet heavy snow near ridge top,
SATURDAY: Broken cloud cover, freezing level holding around 1500 m, moderate to strong west/southwest wind, 1 to 6 cm of snow expected up high, rain down low.
SUNDAY: Broken cloud cover at dawn clearing to just a few clouds in the late afternoon, freezing level beginning at valley bottom rising to 1500 m, light west/southwest wind, no precipitation expected.
MONDAY: A few clouds in the morning building to broken cloud cover in the afternoon, freezing level beginning at valley bottom rising to about 1800 m, moderate to strong west/northwest wind, no significant precipitation expected.
One of our field team members got out for a flight Friday, and she found a slab avalanche on a steep east/southeast facing alpine feature, but aside from that and a bit of loose wet activity on solar aspects, there has been little reported recent avalanche activity.
On Thursday a few small cornice falls were observed near Elkford, one of which triggered a size 2 slab on the slope below. A few small (size 1-1.5) slab avalanches were triggered by skiers on Tuesday and Wednesday, including a small storm slab that may have failed on surface hoar.
The most recent deep persistent slab activity we know about is described in this MIN report from February 11 and this MIN report on February 9.
The 10 to 35 cm of snow from Sunday/Monday was absolutely hammered by wind Wednesday as evidenced in this MIN submission. Wind was strong enough to get into below treeline features even. Then it got quite warm Friday, the freezing level got to at least 2300 m. The beat up old snow is now quite warm. It sits on a variety of old surfaces including a firm crust on solar aspects, soft faceted snow, possibly surface hoar in sheltered areas, and old wind slabs near ridge crest, once it cools off it is unlikely to be much of a problem anywhere.
A thick rain crust sits 30-60 cm below the surface and can be found up to 2100 m. Avalanche activity was last observed at the faceting interface between this crust and overlying snow on February 17.
The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
