Choose simple terrain, and avoid large features. Warm temperatures and sun are forecasted to hit a complicated snowpack. It's a good time to make conservative decisions, and our recent forecasters' blog explains why.
Up to 10 cm of recent snow and strong wind has formed wind slabs that may be reactive to rider triggering.
Sun and warm temperatures all the way into the alpine could keep this problem active. Slabs may be more reactive where they sit on surface hoar or crusts.
Be extra cautious in leeward terrain and convex rolls.
Natural cornice fall is possible with upper elevation warming and solar radiation. Cornice fall could be a hazard on its own and it could trigger a deeper slab avalanche from the slope below.
Loose wet avalanches are possible, especially on southerly aspects and steeper slopes.
The early December crust can be found 90-160 cm deep. A deep persistent slab problem could wake up with forecast warming, solar radiation, cornice fall, and step-downs from smaller avalanches.
A ridge of high pressure brings warming and sunny skies through the weekend. Alpine inversions may see temperatures as high as +1 degrees with valley bottoms seeing some cloud and cooler air pooling at the lower elevations.
Saturday Night: Mostly clear. No new snow expected. Moderate to strong ridge wind from the northwest. Mixed bag of freezing levels across the region, between 2000 m and 3000 m. Cold air pooling in valleys could keep temperatures between 2000 m and 500 m below 0.
Sunday: Mostly clear. No new snow expected. Freezing levels rise through the day to between 1000 m and 1500 m. Ridgetop winds moderate to strong from the northwest.
Monday: Partly cloudy. Possible trace of snow. Moderate to strong ridge wind from the northwest. Freezing level at valley bottom in the morning, rising to 750 m by the afternoon.
Tuesday: Partly cloudy. No new snow expected. Light southwest wind, trending to strong northwest at higher elevations. Freezing level at valley bottom overnight, rising to 600 m by the afternoon.
Most concerning is the warm weather this weekend. Warming, solar radiation, smaller surfaces avalanches, and cornice fall could trigger deep persistent slabs.
On Saturday, two size 1.5 rider triggered wind slab avalanches were reported near Golden. They were on northeast through southeast aspects at treeline and above. Additionally, a natural cornice fall from a south aspect in the alpine triggered a size 2.5 avalanche in extreme terrain that ran into rideable terrain below.
On Friday, explosive triggered wind slabs up to size 2 were reported. Additionally, a natural wind slab cycle up to size 2 was reported but likely from Thursday.
Over the last week, the early December persistent weak layer has produced a few large natural avalanches (2-3) in the center of the region. Explosive controls have also produced a few size 2 avalanches that failed on the same persistent weak layer, one being remotely triggered. These occurred on thin to thick features on northeast-facing slopes from between 1600 m and 2000 m, where the layer was buried 100 cm + deep.
Incoming warm air may ride on top of colder air in the valleys, so the snowpack may experience above zero temperatures at higher elevations, where you may not expect them. Combine this with the potential for strong solar input, and the alpine snowpack could experience some rapid change for the worse.
Up to 10 cm of recent snow and strong winds have formed pockets of reactive wind slab, especially where it sits above surface hoar and crusts.
Around 1900 m and below, a crust is now capping the dense 10-30 cm of snow which has settled significantly with the past mild temperatures. The crust varies from thin to thick, according to the aspect and elevation. Below this, a layer of surface hoar and melt-freeze crusts are found, which seems to be still reactive in isolated areas.
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 90-160 cm. This layer was reactive last weekend producing many large size 3 avalanches from all aspects and elevations.
Activity has tapered, however, warming, cornice fall, and human triggers from steep, rocky slopes, with a shallow or thin-to-thick snowpack may wake it up again this weekend.
