20-30cm of snow is on its way. While not a huge amount, we are expecting a brief natural cycle tomorrow.
Weather Forecast
All forecasts are saying snow is on the way. Amounts vary, but 30cm seems to a common number for the Spray area. Unfortunately moderate to strong southwest winds will accompany the snow. As for temperatures, they will remain warm until later in the week end. Tomorrow's high is -5C. Today saw above zero temps on the road.
Avalanche Summary
Nothing noted today due to poor visibility.
Snowpack Summary
The leading edge of the approaching storm has so far given us only 4cm near the divide. It is exactly what the forecast said would happen (don't hear that much!). That's giving us confidence in there being a further 20cm by tomorrow. The forecasted winds are also correct. As of this afternoon ridgetop winds were around 50km/hr from the SW. Windslabs are building on any easterly aspect in the alpine and treeline areas. How well these slabs stick to the underlying windslabs is the question. Given how long the slabs were exposed for, it may be a poor bond at first. Treeline saw little change today, but again, if there are new slabs by tomorrow expect them to be poorly bonded due to surface facetting. In general, this 20cm would be considered a rapid load. The Jan 17th surface hoar is isolated, but where it exists, expect it to be down 30cm and possibly reactive. Deeper layers will be stressed trying to support the weight of a 20-30cm storm.
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.