Very strong outflow (north) winds have returned to our area.  These are forecasted to be much stronger than the wind event directly following the 12/15 storm.  The increased strength will also mean a greater area is affected.  On 12/22 there were many areas were sheltered powder still existed.  These are the areas that will have the highest hazard today as there is a significant amount of snow for transport and wind speeds should be ripe for building dangerous wind slabs (25-35mph) in these areas.  In places that were previously damaged by wind, such as locations in close proximity to Thompson Pass summit, winds speeds of 60-70 mph are expected.  The avalanche hazard will be less in these areas although remains possible, as there is not as much snow available for transport (already been blown away).  In addition, the strength of winds that are expected will be stripping and sublimating transported snow rather than depositing it.  Where it does get deposited expect to find wind slab formation further down from ridge lines than you may expect.

Either way wind slabs will be forming today and will be initially reactive to human triggers 1-2 feet in depth.

Asses the hazard of this avalanche problem by paying attention to what slopes are loaded, how deep and their sensitivity.  Watch for signs of instability such as shooting cracks and collapsing that would indicate a slope has the potential to produce an avalanche.

Persistent weaknesses in our snowpack will be receiving increased pressure today in specific areas due to wind loaded snow.

Faceted snow near the base of the snowpack has been identified in all three forecast zones. In most locations above brush line, faceted snow is capped by pencil-knife hard wind affected snow.  This has created a strong bridging affect making a person or machines weight unlikely to directly affect these layers. 

Our area received 3-4 inches of snow water equivalent over a 5 day period beginning 12/11.  This put significant stress on these weak layers.  Natural avalanches did occur, but activity was not widespread and natural avalanches were mostly confined to the storm snow.  This points to the strength of the wind hardened snow overlying the weak facets at the base of our snowpack. 

It has been five days since the last significant snowfall event and stability tests that directly target these layers have not produced propagation since.  One exception was an interior location  just north of our continental forecast zone where propagation in stability tests still existed on 12/18.

Persistent weak layers are tricky to assess and are notorious for surprising people.  As long as temperatures remain cold and our snowpack is thin, these weak layers will continue to lose strength.  It is likely that facets will reactivate in the future when stress is being applied through dramatic changes in weather such as: significant snow accumulation, rapid warming and wind loading.  Maintaining safe travel protocols such as skiing one at a time and avoiding traveling in or above terrain traps will increase your safety margin.  

 The most likely areas to trigger a persistent slab avalanche would be in steep terrain that was protected from previous strong winds that have occurred this season. This could be below brushline or in areas of terrain that are typically spared from outflows.  The Continental zone remains suspect as this area has a weaker snowpack and generally receives less wind, which would decrease the bridging affect mentioned above.