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Avalanche Forecast

Archived

Mar 18th, 2021–Mar 19th, 2021

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

Regions

South Columbia.

 

New snow and strong wind may form isolated pockets of fresh wind slab.

The region will see mostly cloud cover on Friday, but if the sun shines it could heat up fast. Pay attention to steep South facing slopes and back off if they heat up

Avoid exposure above or below cornices.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

A Pacific frontal system reaching the Coast today will bring cloudy skies and snowfall to the Interior regions through the weekend.

Thursday Night: Snow 5-10 cm. Ridgetop wind moderate from the southwest and alpine temperatures near -5. Freezing levels 1300 m.

Friday: Cloudy with sunny periods and possibly 5-10 cm. Ridgetop wind strong from the southwest and freezing levels 1700 m.

Saturday: Snow 10 cm. Ridgetop wind strong from the West and alpine temperatures near -8. Freezing levels 1300 m.

Sunday: Snow 5-10 cm. Ridgetop wind light to moderate from the southwest. Freezing levels 1200 m. 

Avalanche Summary

On Wednesday, minimal avalanches were reported. A few loose-wet avalanches were seen on steep solar aspects below treeline. 

On Tuesday, a natural 1.5 loose wet avalanche was reported from steep rocky terrain and small loose-dry sluffs were easily triggered by skier traffic on northerly aspects. 

Snowpack Summary

Isolated wind slabs may form just below ridgelines with new snow and strong wind. Snow surfaces vary at the moment. Surface hoar up to 10 mm in size exists at treeline and above. Sunny skies and warm temperatures formed sun crusts on solar aspects and at all elevations and up to 2000 m on polar aspects. Dry snow still exists on north aspects at upper elevations. Large cornices loom over alpine ridgetops.

Persistent weak layers of surface hoar, crusts, and/or facets 80-120 cm down have recently been unreactive except for an explosives triggered avalanche in the southeast of the region on Saturday. 

Terrain and Travel

  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Use caution above cliffs and terrain traps where even small avalanches may have severe consequences.
  • Cornices become weak with daytime heating or solar exposure.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

Problems

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.