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Avalanche Forecast

Archived

Mar 2nd, 2021–Mar 3rd, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Lizard-Flathead.

This is the first significant warm-up in March and we expect this to complicate current avalanche conditions. Natural avalanche activity will be on the rise as the snowpack heats up. Check out the new Forecaster Blog on warming and the effects on our already complex snowpack

Confidence

Moderate - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

High pressure over the region will bring sunny skies and a significant warm-up. Freezing levels forecast 2000 m to 2500 m.

Wednesday: A mix of sun and cloud. Ridgetop wind light from the southwest. Alpine temperatures near 0 and freezing levels rising 1500-2000 m. 

Thursday: Mostly sunny and ridgetop wind light from the southwest. Alpine temperatures near + 1 and freezing levels 2000-2500 m.

Friday: Mostly sunny and ridgetop wind generally light with strong southerly gusts. Alpine temperatures near + 2 and freezing levels 2000 -2500 m.

Avalanche Summary

No recent avalanche reports for Tuesday.

Sun and warming is our primary concern over the next few days. Large looming cornices may weaken and fail, triggering slabs on the slopes below. Loose-wet avalanches will likely be seen from solar aspects first and then possibly all aspects. The persistent slab sitting above weak layers may stiffen and consolidate further, failing as a natural avalanche or becoming more sensitive to skier and rider triggers. This problem is not healing quickly and the conditions are not easily managed. A conservative mindset and patience are crucial right now.  

Pockets of wind slab may be reactive on northeast-east aspects at upper elavtions. 

Snowpack Summary

Large, looming cornices exist on many ridgelines and threaten slopes below. Strong west-southwest winds have formed wind slabs on leeward slopes while freezing rain formed a widespread breakable crust 1-5 mm below 1800 m and in spotty locations at upper elevations.

Up to 50 cm of snow sits above a variety of old interfaces that formed mid-February and 60-100 cm down is a persistent weak layer that was buried in late January. These mostly include sugary facets, hard wind pressed surfaces, surface hoar in wind-sheltered locations, and sun crust on steep solar aspects. The South Rockies Field Team was near the powder cowboy sled zone today and their snowpack tests showed easy results (CTE 7 SC down 60) on a persistent weak layer.

The weather forecast is concerning with the current snowpack structure. Warming and solar radiation may stiffen and consolidate the slab above the weak layers. Expect surface snow to become moist and weak and large looming cornices overhead may fail, triggering slabs on the slopes below.

Terrain and Travel

  • The trees are not the safe-haven they normally are at this time. Terrain at treeline is primed for human triggered avalanches.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • In times of uncertainty conservative terrain choices are our best defense.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.