Avalanche Forecast
Issued: Apr 16th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet, Cornices and Persistent Slabs.
Conrad Janzen,
We expect to see a lot more avalanche activity on Saturday as this is the hottest day of the spring so far. Avoid all avalanche terrain once the snowpack heats up and be aware that a forecast inversion may be heating upper elevations faster.
Summary
Weather Forecast
An inversion is forecast Friday night with above freezing temperatures all night in the alpine. The clear skies and warm weather will continue until Saturday evening when a cooling trend starts with some precipitation expected on Sunday. Saturday could be "the day" for avalanches. This is the biggest warm up so far this year.
Snowpack Summary
Surface crusts present on solar aspects and all aspects up to 2200 m in the morning, quickly turning to wet snow as the day warms up. High elevation north aspects still holding dry snow. Several persistent layers exist in the mid to lower snowpack from earlier in the winter that may become active layers again over the next 48 hr as things heat up.
Avalanche Summary
On Friday explosive control on the 93 S produced good results up to size 3 with small slabs at treeline gouging into deeper layers at lower elevations and running full path. Widespread natural loose wet avalanche activity up to size 2 was also observed at all elevations. We expect avalanche activity to increase on Saturday.
Confidence
Problems
Loose Wet
Expect widespread wet loose avalanches on Saturday. With the forecast inversion these may start much sooner in the day so plan objectives that allow you to avoid this hazard as the day warms up.
- Daytime warming will weaken surface layers, plan your day around being back to the trailhead early.
- Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are huge and are failing regularly, sometimes triggering deeper layers in the snowpack. With the intense solar input forecasted, they may start to fail even earlier in the day.
- Give cornices a wide berth when traveling on ridges.
- Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
Be wary of large slab avalanches Saturday as the heat penetrates deep into the snowpack and starts to wake up some old persistent weak layers. These may run to the bottom of run out zones in the right terrain features.
- Pay attention to overhead hazards like cornices which could trigger persistent slabs.
- Pockets of persistent slabs linger on alpine lee features.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 17th, 2021 4:00PM
