Wind slab is the main concern for the weekend. Watch for reactive wind slabs in lee and cross-loaded terrain features at upper elevations.
Recent snow has been redistributed into lee and cross-loaded terrain features by primarily west and northwest wind. Wind slabs may be especially reactive where they sit over a crust which makes a slick be surface for avalanches. Watch for shooting cracks as an indicator of reactivity in wind-stiffened snow.
Cornices have grown with recent moderate winds. Cornice falls can be dangerous on their own and they can also trigger wind slabs on slope below. Give them a wide berth when travelling on or below ridgetops.
Wind slab avalanches size 1-2 have been observed over the last few days on north to east facing slopes in the alpine. Some of them are suspected to have been triggered by cornice falls.
Recent snowpack test results and signs of instability like shooting cracks reported in recent MINs also suggest instability in wind slabs.
Variable snow conditions exist at upper elevations due to extensive wind affect by sustained moderate west to northwest winds. Soft snow can still be found in sheltered areas like in trees, gullies and bowls.
A widespread near-surface crust has been described in nearly every MIN report this week (thank you!). It sits on the surface in scoured, windward features; an average of 10 cm deep in sheltered areas; and up to 30 cm deep in wind-loaded areas. Some faceting has been observed above the crust which has created a weak layer for overlying wind slabs to fail.
The snow below is a mix of dense wind affected snow layers at higher elevations. At lower elevations you may find another thin melt freeze crust 50+ cm deep. The lower snowpack is likely dense and well bonded from warm temperatures, rainfall and subsequent refreezing.
Friday night
A trace of snow. Moderate to strong northwest wind. Alpine low -14 C.
Saturday
A mix of sun and cloud with isolated flurries bringing a trace of snow. Moderate to strong northwest wind. Alpine temperature -15 C.
Sunday
5-10 cm of new snow. Moderate to strong northwest wind, switching northeast in the evening. Temperatures warming through the day, reaching 0 C in the alpine by late evening.
A "backdoor warm front" associated with an atypically tracking low pressure center moving west-to-east is casting great uncertainty on the weather forecast beyond the weekend. Weather models vary greatly from one run to the next so stay tuned for updates. Likely weather features include above zero temperatures, mixed precipitation and strong east to northeasterly winds.
More details can be found in the Mountain Weather Forecast.
