Watch for pockets of wind slab on various aspects in exposed terrain and around ridgelines.
There is recent evidence that the persistent avalanche problem can still be human triggered in parts of our region.
Watch for pockets of wind slab on various aspects in exposed terrain and around ridgelines. Recent northeast winds have reverse loaded features building slabs in less common places.
These slabs have formed on top of old crusts and hard wind-pressed snow and there is uncertainty about how quickly they will bond to old surfaces.
Persistent slab avalanches are possible, mostly on shaded aspects, due to a layer of buried surface hoar around 40-60 cm deep. This problem is tricky to pin down because of its spotty distribution (it isn't a problem everywhere). It has been most reactive recently in the Flathead with reports of rider triggering (see MIN post), whumpfing and propagation in snowpack tests.
Steep open areas at treeline and below that are sheltered from the wind and haven't seen much rider compaction over the last month are the most suspect.
WEDNESDAY NIGHT: Light flurries overnight. Light southwest winds. Alpine lows of -20.
THURSDAY: Partly cloudy, light northwest wind, alpine high of -11.
FRIDAY: Mix of sun and cloud. Light to moderate southwest wind. Alpine highs of -10.
SATURDAY: Mix of sun and cloud, moderate southwest wind, alpine highs of -7.
On Tuesday there was a small natural wind slab reported in the Lizard Range, as well as some small (size 1) skier-controlled wind slabs. On Monday a skier accidentally triggered a wind slab on a reverse loaded feature in the Lizard Range (MIN here). On Saturday there was a machine triggered avalanche on an old buried surface hoar layer in an open gully feature in the Rolling Hills area.
The 10-30 cm of most recent snow has been redistributed by recent moderate to strong northeast winds and formed wind slabs in unusual places. In south-facing terrain, new snow sits on top of melt-freeze crusts, and in open terrain recent snow sits over old firm wind-affected surfaces.
A buried surface hoar layer may be found 30-60 cm deep on sheltered, north-facing treeline-type features. This distribution of this layer is spotty in nature but has recently produced avalanches, whumpfing and snowpack test results in the Flathead.
The lower snowpack is well consolidated, with a crust/facet layer found near the bottom of the snowpack. It is currently considered dormant but could become active later this season. Check out the forecaster blog for more information.
