Regions
Northwest Inland.
Confidence
Fair - Forecast snowfall amounts are uncertain on Wednesday
Weather Forecast
Clear skies and cold temperatures are forecast for Monday night. Cloud should start to build during the morning as the wind veers to the west and increases to moderate. Expect about 2-5 cm of snow Tuesday afternoon and another 5 cm by Wednesday morning. Wednesday is expected to be unsettled with flurries, moderate winds, and rising freezing levels. A warm front should move in from the Pacific on Thursday bringing strong southerly winds, high freezing levels, and heavy precipitation.
Avalanche Summary
We have a report of a natural size 2.5 on a North aspect in "Big Simpsons Gulch" that ran from the crater lake ridge and triggered a size 2.0 on a ESE aspect lower down and then triggered a size 2.0 slab below the big cliffs. We are not sure how old this avalanche is, and believe that it was the result of a cornice fall.
Snowpack Summary
Moderate southwest winds transported the 3-5 cm of new snow that we have received over the past two days into thin new windslabs at ridgetops. Currently, up to 60cm of snow sits over the mid February interface. This interface is variable, it consists of a strong melt freeze crust below 1000m, above 1000 m exists facets, surface hoar (in more sheltered areas), sun crust or wind press. The surface hoar is not widespread but is responsible for much of the larger avalanches that occurred earlier this week. This layer should be on your radar, as it may be susceptible to rider triggers.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.