Avalanche Forecast
Issued: Apr 13th, 2021 4:06PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet, Persistent Slabs and Cornices.
Lisa Paulson,
Wednesday will start with LOW hazard, but intense solar radiation and rising freezing levels will raise the hazard. Start and finish early, and avoid steep solar aspects and terrain threatened by cornices as they warm up.
Summary
Weather Forecast
Light easterly winds & sunny skies continue for Wednesday. Freezing levels will rise to 2500 m with intense solar inputs expected at all elevations during the day. Good overnight freezes with slowly increasing freezing levels and lots of solar inputs are expected for the next several days as we progress to the spring diurnal hazard rating.
Snowpack Summary
15 to 30 cm of storm snow at treeline with more at higher elevations. Buried crusts up to 1800m on all aspects and to ridge crest on solar aspects. Small wind slabs in alpine lee areas. Several persistent layers exist in the mid to lower snowpack that might be a concern in thin areas with significant warming or with larger triggers like cornices.
Avalanche Summary
One size 3 deep persistent slab triggered by cornice failure at 10 am today on Mt. Stanley. Another size 2.5 cornice triggered slab on the Mt. Whymper from Monday afternoon. Several loose dry avalanches observed with in steep terrain as the sun warmed the surface. A few days ago, storm snow failed on a buried crust so this is worth monitoring.
Confidence
Problems
Loose Wet
With intense solar inputs expected and lots of loose snow on solar aspects, we expect many loose wet avalanches over the next few days. Keep an eye on any sun exposed terrain above you and be off steep solar terrain before these start.
- 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: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Warming temperatures may cause this problem to start showing up again. Significant solar warming , high alpine thin snowpack areas or places where a large cornice might have enough punch to trigger the deeper layers are the main areas of concern.
- Pockets of persistent slabs linger on alpine lee features.
- Pay attention to overhead hazards like cornices which could trigger persistent slabs.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Cornices
Cornices are huge and are failing triggering deeper persistent layers in the snowpack. With the intense solar input forecasted, they may start to fail early in the day.
- Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.
- Give cornices a wide berth when traveling on ridges.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 14th, 2021 4:00PM
