New precipitation and warm temperatures means natural avalanches are possible and human-triggered avalanches are likely today.
Weather Forecast
A frontal system will bring strong southwest winds and precipitation to Rogers Pass today. Models suggest 10-15cm of snow could fall by this evening, but only at higher elevations. Freezing levels are already above 1900m and are expected to rise to 2000m. The system moves out of the area late tonight, beginning a period of high pressure.
Snowpack Summary
Isothermal snow in the valley bottom did not refreeze overnight and received 4mm of rain this morning. Above 1900m, 10cm of new snow fell with moderate southerly winds. Widespread and reactive wind slabs in exposed areas are now buried. Crusts in the top 30cm are weakening with continued warm temps and triggering of deeper layers is possible.
Avalanche Summary
A natural cycle of loose wet avalanches yesterday afternoon in the highway corridor. Avalanches started in moist, high alpine start zones and ended with wet deposits up to size 2.5. Wind slab avalanches were observed on the north face of Mt Cheops to size 1.5. On Dome Glacier, a size 2.0 wind slab was triggered by the 5th skier on the slope.
Confidence
Intensity of incoming weather systems is uncertain
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.