Regions
Northwest Inland.
Snow, wind, and warming are on the menu this week. Expect slabs to build and avalanche danger to rise.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Synopsis: The storm track looks like it will be aimed squarely at the Northwest for the next few days bringing a series of frontal systems. Expect 5-15 cm of snow on Tuesday, another 15-30 cm (or mm) Tuesday night through Wednesday, and it keeps coming down on Thursday. We should see a warming trend with freezing levels around 500-1000 m on Tuesday, and 1500-1700 m on Wednesday/Thursday. Winds should be consistently moderate or strong from the SW.
Avalanche Summary
A couple size natural size 2 wind slabs were reported from steep wind loaded terrain (northeast facing) on Sunday.
Snowpack Summary
Strong southerly winds are building wind slabs, generally depositing snow on N and NE aspects (other aspects may be getting cross-loaded or variable local wind effects too, so keep your eyes open). A surface hoar layer was reported to have been buried at the start of January in the northern part of the region. In the mid-pack, a crust weakness buried in mid-December seems to have fallen off most operators' radar for now. Near the base of the snowpack is a November crust-facet combination that could remain problematic, especially in shallower snowpack areas.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.