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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

South Rockies.

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.

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 strong from the southwest. Alpine temperatures near + 3 and freezing levels 2000-2500 m.

Friday: Mostly sunny and ridgetop wind strong from the southwest. Alpine temperatures near + 2 and freezing levels 2000 -2500 m.

Avalanche Summary

No recent avalanche reports on 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 above the 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

Upper elevations are highly wind-affected and scouring down to rocks or crusts can be seen on west to southwest aspects. On leeward (northeast-east) slopes, stiff wind-slab has formed at treeline and in the alpine.

40 to 60 cm (in some places up to a meter) of snow now sits above sugary faceted snow that formed mid-February. Snowpack testing done by the South Rockies Field Team last Saturday in the Mear Lake area showed a relatively easy to moderate failure on the mid-Feb layer which propagated across the whole column (ECTP 13 down 40 cm). This test was on a south-facing slope at treeline and shows the sensitivity of this weak layer. Deeper in the snowpack (60 to 100 cm deep) is yet another weak layer that was buried at the end of January. This layer consists of surface hoar, faceted grains, and/or a hard melt-freeze crust. MIN reports prove these layers remain easily triggered by people. 

Weak faceted grains and a decomposing melt-freeze crust can be found near the base of the snowpack. 

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.
  • Choose simple, low-angle, well supported terrain without convexities.
  • 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.

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.