Another hot day with a limited overnight freeze may initiate a spike in wet loose and possibly larger wet slab avalanche activity. Start and finish your day early and avoid sun-exposed terrain. Don't linger in runout zones and steer clear of cornices from above and below.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
Wednesday: A mix of sun and cloud. Ridgetop wind generally light. Alpine temperatures near +7 C and freezing levels 2500 m.
Thursday: A mix of sun and cloud. Ridgetop wind light from the northwest. Alpine temperatures near +5 C. Freezing levels 2500 m.
Friday: Mostly cloudy with some sun. Ridgetop winds light from the South. Alpine temperatures +6 C and freezing levels 2400 m.Â
Avalanche Summary
No new reports on Monday.Â
Last weekend, reports of natural loose wet avalanches size 2-3 on solar aspects continued. Explosive work produced size 2-3.5 wet slab avalanches, failing on crusts in the upper snowpack and gouging to the ground as they ran to near valley bottom.
With all of this heat, sunshine, and little overnight crust recovery, I suspect this type of avalanche activity will continue through the forecast period. It's crucial to start early and end your day early as well as avoid solar slopes and cornices.Â
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Snowpack Summary
The snow surface consists of a melt-freeze crust on solar aspects and shaded aspects into the lower alpine, which transitions into moist/wet snow during the day. With a limited freeze overnight on Tuesday, this crust may break down even faster (by noon) with mostly wet snow surfaces on Wednesday. Dry snow might still be found on northerly aspects in the high alpine. There are no layers of concern in the snowpack, which has been melting and settling over the past week.Â
Large cornices loom along many ridgelines.Â
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Terrain and Travel
- Avalanche hazard is expected to to increase througout the day, think carefully about your egress.
- Keep in mind that wet avalanches can be destructive due to their high density.
- Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
- Avoid lingering or regrouping in runout zones.
Problems
Loose Wet
Wet loose avalanche activity can also be expected on sun-exposed slopes. These avalanches are generally smaller than wet slabs but they can gather mass as they travel and reach low elevations.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wet Slabs
The likelihood of wet slab avalanches increases during prolonged periods of warm temperatures, as the heat penetrates deeper into the snowpack. These avalanches are dense, destructive, and can run far, reaching otherwise snow-free valley bottoms.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are at their largest at this time of year, and become weaker with warm temperatures and solar radiation.
Aspects: North, North East, East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 21st, 2021 4:00PM
